Patent Publication Number: US-2009234453-A1

Title: Implant devices

Description:
REFERENCE TO RELATED APPLICATIONS 
     The present application is related to U.S. Provisional Patent Application Ser. No. 60/662,940 filed Mar. 17, 2005, and entitled IMPLANT DEVICES, the disclosure of which is hereby incorporated by reference and priority of which is hereby claimed pursuant to 37 CFR 1.78(a) (4) and (5)(i). 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to orthopedic implants generally and to methodologies and tools useful therewith. 
     BACKGROUND OF THE INVENTION 
     The following patent publications, the disclosures of which are hereby incorporated by reference, are believed to represent the current state of the art: 
     PCT Patent Application Publication Nos.: WO 97/10776; WO 98/46169; WO 00/053077; WO 2003/047470 and WO 2003/099156 
     SUMMARY OF THE INVENTION 
     The present invention seeks to provide improved orthopedic implants as well as methodologies and tools useful therewith. 
     There is thus provided in accordance with a preferred embodiment of the present invention an orthopedic implant including an implant element adapted to be attached to at least one bone, the implant element including at least one throughgoing bone growth region adapted to be located in bone growth communication with the at least one bone and configured such that bone growth therein creates a grown bone suture binding the implant element to the at least one bone. 
     There is also provided in accordance with another preferred embodiment of the present invention an orthopedic implant including a resilient implant element adapted to be attached to at least one bone, the implant element including at least one bone growth region adapted to be located in bone growth communication with the at least one bone and configured such that bone growth therein creates a grown bone lock binding the resilient implant element to the at least one bone. 
     There is further provided in accordance with yet another preferred embodiment of the present invention an orthopedic implant including an implant element adapted to be attached to at least one bone, the implant element including at least one bone growth region adapted to be located in bone growth communication with the at least one bone and containing grown bone enhancing material configured such that bone growth therein creates a grown bone lock binding the implant element to the at least one bone. 
     Preferably, the grown bone enhancing material includes bone growth enhancing material. Alternatively, the grown bone enhancing material includes grown bone reinforcing material. 
     In accordance with a preferred embodiment the implant element is a glenoid socket element. Alternatively, the implant element is an elbow joint implant element. Further alternatively, the implant element is a hip joint implant element. In another alternative embodiment, the implant element is a knee joint implant element. In an additional alternative embodiment, the implant element is a spinal disc implant element. 
     Preferably, the at least one bone growth region contains a resorbable material. Additionally or alternatively, the at least one bone growth region contains a resorbable grown bone enhancing material. Additionally, the resorbable grown bone enhancing material includes at least one of a bone substitute, a synthetic matrix substitute, a BMP material, a PTH material, a bisphosphonate material, a receptor agonist material and a bone graft substitute. 
     Preferably, the implant element also includes reinforcement elements located in the at least one bone growth region. Additionally or alternatively, at least part of the at least one bone growth region is formed with an undercut in order to enhance grown bone locking thereat. 
     Preferably, the at least one bone growth region also includes at least one drug supply channel, the at least one drug supply channel containing a drug which it is sought to supply to at least one location on the at least one bone. Additionally, the drug is in a timed-release dosage form. Additionally or alternatively, the drug is at least one of a taxane, an alkylating agent and an anthracycline. 
     In another preferred embodiment, the implant is a grown bone locked splint implant. Additionally, the grown bone locked splint implant includes a plurality of throughgoing bone growth regions adapted to be located in bone growth communication with portions of the at least one bone and configured such that bone growth therein creates a grown bone suture binding the grown bone locked splint implant to the portions of the at least one bone. Additionally or alternatively, the grown bone locked splint implant is resilient. 
     Additionally or alternatively, the grown bone locked splint implant is adapted to be attached to the portions of the at least one bone and configured such that the bone growth creates a grown bone lock binding the grown bone locked splint implant to the at least one bone. Additionally or alternatively, the plurality of bone growth regions include grown bone enhancing material such that the bone growth creates a grown bone lock binding the grown bone locked splint implant to the at least one bone. 
     In accordance with a preferred embodiment the grown bone locked splint implant is a humerus splint implant and includes a grown bone locked humerus splint implant element arranged to surround portions of the humerus. Alternatively, the grown bone locked splint implant is a femur splint implant and includes a grown bone locked femur splint implant element arranged to surround portions of the femur. Further alternatively, the grown bone locked splint implant is a tibia splint implant and includes a grown bone locked tibia splint implant element arranged to surround portions of the tibia. 
     Additionally or alternatively, the grown bone locked splint implant is in the form of a split cylinder, formed of a somewhat resilient material, and includes a plurality of elongate reinforcing strips, formed of a generally non-stretchable material, embedded therein. Additionally, the split cylinder has formed therein a plurality of throughgoing bone growth regions which encircle at least one of the reinforcing strips. Additionally or alternatively, the grown bone locked splint implant includes reinforcement elements which encircle at least one of the plurality of reinforcing strips. 
     Preferably, the grown bone locked splint implant is useful for broken elongated bones as well as for weakened bones. 
     There is also provided in accordance with another preferred embodiment of the present invention an orthopedic implant including a ligament attachment assembly adapted to be attached to at least one bone and at least one ligament, the ligament attachment assembly including at least one ligament attachment element having at least one throughgoing bone growth region adapted to be located in bone growth communication with the at least one bone and configured such that bone growth therein creates a grown bone suture binding the at least one ligament attachment element to the at least one bone. 
     There is further provided in accordance with still another preferred embodiment of the present invention an orthopedic implant including a ligament attachment assembly adapted to be attached to at least one bone, the ligament attachment assembly including at least one ligament attachment element having at least one bone growth region adapted to be located in bone growth communication with the at least one bone and configured such that bone growth therein creates a grown bone lock binding the at least one ligament attachment element to the at least one bone. 
     There is yet further provided in accordance with yet another preferred embodiment of the present invention an orthopedic implant including a ligament attachment assembly adapted to be attached to at least one bone, the ligament attachment assembly including at least one ligament attachment element having at least one bone growth region adapted to be located in bone growth communication with the at least one bone and containing grown bone enhancing material configured such that bone growth therein creates a grown bone lock binding the at least one ligament attachment element to the at least one bone. 
     Preferably, the grown bone enhancing material includes bone growth enhancing material. Alternatively, the grown bone enhancing material includes grown bone reinforcing material. 
     Preferably, the at least one bone growth region contains a resorbable material. Additionally, the at least one bone growth region contains a resorbable grown bone enhancing material. Additionally, the resorbable grown bone enhancing material includes at least one of a bone substitute, a synthetic matrix substitute, a BMP material, a PTH material, a bisphosphonate material a receptor agonist material and a bone graft substitute. 
     Preferably, the orthopedic implant also includes reinforcement elements located in the at least one bone growth region. Additionally or alternatively, at least part of the at least one bone growth region is formed to engage an undercut in bone in order to enhance grown bone locking thereat. 
     In accordance with a preferred embodiment the ligament attachment assembly is a knee ligament attachment assembly. Alternatively, the ligament attachment assembly is a hip ligament attachment assembly. Further alternatively, the ligament attachment assembly is a shoulder ligament attachment assembly. 
     Preferably, the ligament attachment assembly includes a plurality of ligament attachment elements, each adapted to have looped therearound, at a ligament loop retaining location thereof, a closed looped ligament end. Additionally, the closed loop ligament ends are formed of at least one of natural ligaments, artificial ligaments and portions thereof. Additionally or alternatively, the plurality of ligament attachment elements are formed of or include bone growth enhancement materials. Additionally or alternatively, the each of the plurality of ligament attachment elements is adapted to be located in bone growth communication with a bone surface and configured such that bone growth therein creates a grown bone ligament anchor. 
     In accordance with another preferred embodiment, the ligament attachment assembly includes multiple ligament attachment elements and a ligament attachment element positioner. Additionally, the ligament attachment element positioner includes an elongate element formed with a generally conical surface at an inner end thereof. Additionally, the ligament attachment element positioner has first and second operative orientations, the first operative orientation where the generally conical surface is generally decoupled from the multiple ligament attachment elements and allows them to lie at a relatively radially inward position for insertion into a hole formed into bone and the second operative orientation where the generally conical surface engages inner surfaces of the multiple ligament attachment elements and forces the implant elements radially outwardly such that respective first surfaces of the multiple ligament attachment elements engage a first circumferential bone surface of an undercut formed in the at least one bone and respective second surfaces of the multiple ligament attachment elements engage a second circumferential bone surface of the undercut. 
     In another preferred embodiment, the multiple ligament attachment elements are adapted such that following insertion of the ligament attachment assembly and positioning of the ligament attachment element positioner in the second operative orientation, bone growth may take place while the multiple ligament attachment elements are retained such that the respective first surfaces of the multiple ligament attachment elements engage the first circumferential bone surface of the undercut and the respective second surfaces of the multiple ligament attachment elements engage the second circumferential bone surface of the undercut. 
     There is also provided in accordance with another preferred embodiment of the present invention an orthopedic implant including a conformal, resilient element adapted to be inserted between respective articulating joint surfaces of a patient, the conformal resilient element including at least one position maintaining engagement portion for attachment to patient tissue in the vicinity of the articulating joint surfaces. 
     Preferably, the conformal, resilient element is a generally thin element formed of a flexible resilient material and is adapted to be generally surrounded by synovial fluid when implanted. Additionally or alternatively, the conformal, resilient element is formed with at least one throughgoing channel for passage of synovial fluid therethrough in response to changes in fluid pressure resulting from joint articulation and the application of changing forces to a joint. Additionally or alternatively, the conformal, resilient element is operative to decrease or eliminate frictional engagement between the articulating joint surfaces. Alternatively or additionally, the conformal, resilient element is operative to enhance desired cartilage regeneration along at least one of the articulating joint surfaces. 
     In accordance with a preferred embodiment, the conformal, resilient element is adapted for implantation in a shoulder joint. Alternatively, the conformal, resilient element is adapted for implantation in an elbow joint. Further alternatively, the conformal, resilient element is adapted for implantation in a hip joint. In another alternative embodiment, the conformal, resilient element is adapted for implantation in a knee joint. In an additional alternative embodiment, the conformal, resilient element is adapted for implantation in an ankle joint. 
     Preferably, the conformal, resilient element is a generally cup-shaped element having an outer facing circumferential protrusion arranged to be loosely seated in a corresponding recess in a surgically reamed socket, with synovial fluid being interposed between the cup-shaped element and the surgically reamed socket and between the cup-shaped element and a corresponding ball. Additionally or alternatively, the conformal, resilient element is formed of polyurethane. 
     In another alternative embodiment, the conformal resilient element is formed with throughgoing respective non-inclined and inclined passageways to allow synovial fluid to pass therethrough and a relatively thin and highly resilient membrane portion which functions as a synovial fluid pump in response to articulation of the articulating joint surfaces and variations in synovial fluid pressure thereat, thereby enhancing synovial fluid flow through the passageways and reducing friction between the articulating joint surfaces. 
     Preferably, the conformal resilient element is constructed that immediately following surgical insertion, the shape thereof does not necessarily conform to the corresponding shapes of the articulating joint surfaces and following at least some articulation of the articulating joint surfaces, the shape of the conformal resilient element increasingly conforms to the corresponding shapes of the articulating joint surfaces. Additionally or alternatively, the conformal, resilient element is constructed that during steady-state, long term use, the conformal, resilient element floats in synovial fluid between the articulating joint surfaces. Alternatively, the conformal, resilient element is constructed that during steady-state, long term use, the conformal, resilient element partially floats in synovial fluid between the articulating joint surfaces and partially contacts at least one of the articulating joint surfaces. 
     Preferably, the conformal, resilient element includes at least one inclined passageway, which provides synovial fluid communication between a first synovial fluid region between the conformal, resilient element and a surgically reamed socket and a second synovial fluid region between the conformal, resilient element and a corresponding ball. 
     In another preferred embodiment, the conformal, resilient element includes at least one membrane portion defining a synovial fluid pump operative to cause micro-rotation of the conformal, resilient element relative to a socket. Additionally or alternatively, the conformal, resilient element is formed of a liquid absorbing structural material. 
     Preferably, the conformal, resilient element is also formed with at least one tab having a protrusion adapted to be seated in a corresponding socket surgically formed in a bone. Additionally, engagement of the tab in the socket is snap-fit engagement. Additionally or alternatively, the conformal, resilient element is arranged to be implanted in a knee joint wherein synovial fluid is interposed between the conformal, resilient element and the tibia and between the conformal, resilient element and a corresponding femoral condyle. 
     Alternatively, the conformal, resilient element is also formed with at least one tab having a resilient protrusion adapted to be seated in a corresponding socket surgically formed in a bone. 
     Additionally or alternatively, the conformal, resilient element is also formed with at least one tab having an extendible protrusion adapted to be seated in a corresponding socket surgically formed in a bone. 
     There is further provided in accordance with yet another preferred embodiment of the present invention an orthopedic implant including a resilient, at least partially hollow, meniscus implant element adapted to be inserted between respective articulating knee joint surfaces of a knee joint of a patient, the resilient meniscus implant element including at least one position maintaining engagement portion for attachment to patient tissue in the vicinity of the articulating knee joint surfaces. 
     Preferably, the meniscus implant element is a generally thin element formed of a flexible resilient material and is adapted to be generally surrounded by synovial fluid when implanted. Additionally or alternatively, the meniscus implant element is formed with at least one throughgoing channel for passage of synovial fluid therethrough in response to changes in fluid pressure resulting from articulation of the knee joint surfaces and the application of changing forces to the knee joint. 
     Preferably, the meniscus implant element is operative to decrease or eliminate frictional engagement between the articulating knee joint surfaces of the knee joint. Additionally or alternatively, the meniscus implant element is operative to enhance desired cartilage regeneration along at least one of the articulating knee joint surfaces. 
     Preferably, the meniscus implant element is formed of polyurethane. 
     In another preferred embodiment, the meniscus implant element is formed with throughgoing passageways to allow synovial fluid to pass therethrough and functions as a synovial fluid pump in response to articulation of the knee joint and variations in synovial fluid pressure thereat, thereby enhancing synovial fluid flow through the passageways and reducing friction in the knee joint. 
     Preferably, the meniscus implant element is constructed so that immediately following surgical insertion, the shape thereof does not necessarily conform to the corresponding shapes of the articulating joint surfaces and following at least some articulation of the knee joint, the shape of the meniscus implant element increasingly conforms to the corresponding shapes of the articulating joint surfaces. Additionally or alternatively, the meniscus implant element is constructed that during steady-state, long term use, the meniscus implant element floats in synovial fluid between the articulating knee joint surfaces. Alternatively or additionally, the meniscus implant element is constructed that during steady-state, long term use, the meniscus implant element partially floats in synovial fluid between the articulating joint surfaces and partially contacts at least one of the articulating joint surfaces. 
     Preferably, the meniscus implant element includes at least one inclined passageway, which provides synovial fluid communication between a first synovial fluid region between the meniscus implant element and a surgically reamed socket and a second synovial fluid region between the meniscus implant element and a corresponding ball. 
     In another preferred embodiment, the meniscus implant element includes at least one membrane portion defining a synovial fluid pump operative to cause micro-rotation of the meniscus implant element relative to a socket. 
     Preferably, the meniscus implant element is formed of a liquid absorbing structural material. 
     Additionally or alternatively, the meniscus implant element is also formed with at least one tab having a protrusion adapted to be seated in a corresponding socket surgically formed in a bone. Alternatively or additionally, the meniscus implant element is also formed with at least one tab having a resilient protrusion adapted to be seated in a corresponding socket surgically formed in a bone. Additionally, engagement of the tab in the socket is snap-fit engagement. Additionally or alternatively, the meniscus implant element is arranged to be implanted in a knee joint wherein synovial fluid is interposed between the meniscus implant element and the tibia and between the meniscus implant element and a corresponding femoral condyle. 
     Preferably, the meniscus implant element is also formed with at least one tab having an extendible protrusion adapted to be seated in a corresponding socket surgically formed in a bone. Additionally or alternatively, the meniscus implant element is configured such that articulation of the knee joint may serve to enhance desired cartilage regeneration along one or both of the knee joint articulating surfaces. 
     Preferably, the meniscus implant element is conformal. Additionally or alternatively, the meniscus implant element is at least one of a medial meniscus implant and a lateral meniscus implant. 
     Preferably, the meniscus implant element is formed of a liquid absorbing material. Additionally or alternatively, the meniscus implant element is a generally kidney-shaped, partially hollow generally flat element. 
     Preferably, the meniscus implant element includes at least one resilient protrusion arranged to be tightly seated in a corresponding socket, surgically formed in the tibia. Additionally or alternatively, the meniscus implant element is formed with at least one tab having a resilient protrusion arranged to be tightly seated in a corresponding socket, surgically formed in the tibia. 
     In another preferred embodiment, the meniscus implant element includes a hollow portion which tapers down to a relatively thin non-hollow portion along a transition line. Additionally, the orthopedic implant also includes at least one valve communicating with the hollow portion. Additionally, or alternatively, the orthopedic implant also includes a fluid at least partially filling the hollow portion. 
     Preferably, the orthopedic implant also includes apertures formed in at least one wall defining the hollow portion to enable synovial fluid to readily communicate therethrough and to be pumped by changes in the volume of the interior of the hollow portion resulting from articulation of the knee joint. 
     Preferably, the meniscus implant element includes folded-over sheet material Additionally or alternatively, the meniscus implant element includes a pair of generally web-type elements which are joined along two seams. Alternatively or additionally, the meniscus implant element includes at least one shape stabilizing internal structural element which cooperates with a polymerizeable material in the interior of a hollow portion thereof to help maintain a desired three-dimensional shape of the implant notwithstanding articulation of the knee joint. 
     There is still further provided in accordance with a further preferred embodiment of the present invention an orthopedic implant including a shock-absorbing ball assembly including a stem mounting portion and a multi-layer shock-absorbing, ball-defining portion defining a generally ball-shaped articulating surface. 
     Preferably, the ball assembly is formed with at least one throughgoing channel for passage of synovial fluid therethrough in response to changes in fluid pressure resulting from joint articulation and the application of changing forces to a joint. Additionally or alternatively, the ball assembly is configurable in situ to provide an individualized fit with a socket. Additionally, the ball assembly is configured to enhance desired cartilage regeneration along an articulating surface of a socket. 
     In accordance with a preferred embodiment the ball assembly is adapted for implantation in a shoulder joint. Alternatively, the ball assembly is adapted for implantation in a hip joint. 
     Preferably, the ball assembly is a generally ball-shaped, partially hollow multi-layer assembly arranged to be tightly seated onto a top portion of a conventional replacement stem. 
     In accordance with a preferred embodiment the ball assembly includes a replacement stem socket having an outer facing rim, a generally ball shaped hollow element fixed to the stem socket and defining an articulating surface, a core element, disposed within the hollow element and at least one relatively thin reinforcing layer located between the hollow element and the core element. 
     Preferably, the core element is formed with at least one synovial fluid void. Additionally, the core element is formed with at least one first synovial fluid communication passageway which communicates with the at least one void and a location adjacent the outer facing rim. Additionally, the core element is formed with at least one second synovial fluid communication passageway which communicates between at least one void through the core element, the at least one reinforcing layer and the hollow element with the articulating surface, thus providing synovial fluid communication with the articulating surface. 
     Preferably, the orthopedic implant also includes at least one one-way flow valve associated with at least one of the first and second synovial fluid communication passageways, whereby pumping action produced by articulation of the ball assembly relative to a socket causes a relatively large amount of synovial fluid to be provided in an articulation region between the articulating surface of the ball assembly and a corresponding articulating surface of the socket. Additionally, the pumping action is constrained by the at least one one-way flow valve such that synovial fluid flows towards the at least one void only via the at least one first passageway and from the at least one void to the articulation region only via the at least one second passageway. 
     Preferably, the orthopedic implant also includes at least one selectably inflatable, selectably expandable void. Additionally, the at least one selectably inflatable void is located so as to underlie most of a generally spherical articulating surface defined by the ball assembly. 
     In another preferred embodiment, the orthopedic implant also includes a spherical radius determining material passageway communicating with the selectably inflatable void to enable a spherical radius determining material to be selectably inserted into the selectably inflatable void in order to enable adaptation of the overall radius of the generally spherical articulating surface in situ so as to provide individualized fit of the ball implant to a patient&#39;s socket. 
     Preferably, the orthopedic implant also includes at least one fluid-filled void. 
     There is even further provided in accordance with yet another preferred embodiment of the present invention a surgical groove reamer including a central bone anchor element including a generally spherical bone engagement surface and a central shaft extending along a longitudinal axis, the central shaft having a first threaded portion thereon, a rotational driving assembly, mounted for rotation about the central shaft and including a first handle fixedly associated with an elongate hollow shaft, which is sized to rotationally accommodate the central shaft, the hollow shaft terminating in a rotational driving plate, a rotational and axial driving element, coupled for rotation together with the rotational driving plate, the rotational and axial driving element including a second threaded portion, which threadably engages the first threaded portion. 
     Preferably, the rotational driving plate is formed with a plurality of axially extending portions which extend into corresponding axially extending sockets formed in the rotational and axial driving element. Additionally, the rotational driving plate is formed with a plurality of first slidable knife support channels and the rotational and axial driving element is formed with a plurality of correspondingly positioned second slidable knife support channels, which extend generally at an angle with respect to the plurality of first slidable knife support channels. 
     In another preferred embodiment the surgical groove reamer also includes a plurality of knives, each slidably seated in a corresponding pair of the first and second slidable knife support channels and mounted on a resilient knife support which permits simultaneous radially outward and rotational displacement of the knives in response to simultaneous axial and rotational movement of the rotational and axial driving element in threaded engagement with the first threaded portion in response to rotation of the first handle. 
     Preferably, the surgical groove reamer also includes a radially displaceable bone engagement assembly including a plurality of flexible engagement elements, each including a hand engageable portion, lying intermediate first and second retaining portions and a radial bone engaging tooth portion. Additionally, the radially displaceable bone engagement assembly includes plural integrally formed flexible engagement elements which are held together about the hollow shaft at respective first and second retaining portions thereof by a corresponding pair of retaining bands to collectively define a second handle at hand engageable portions thereof. 
     Preferably, the surgical groove reamer is operative such that an operator grasping the second handle with one hand causes bending of the plurality of flexible engagement elements about the first and second retaining portions, causing the bone engaging tooth portions to be displaced radially outwardly into retaining engagement with walls of a bone socket being reamed. 
     There is also provided in accordance with still another preferred embodiment of the present invention a socket implanting assembly including a socket implant assembly including inner and outer implantable socket elements and a socket element mounting assembly adapted for preassembly with the inner and outer implantable socket elements and an implanter tool operative with the socket implant assembly for implanting the implantable socket elements in a reamed socket in a patient&#39;s joint. 
     There is further provided in accordance with another preferred embodiment of the present invention a socket implanting assembly including an implanter tool useful with a socket implant assembly including inner and outer implantable socket elements and a socket element mounting assembly adapted for preassembly with the inner and outer implantable socket elements for implanting the implantable socket elements in a reamed socket in a patient&#39;s joint. 
     There is yet further provided in accordance with still another preferred embodiment of the present invention a socket implanting assembly for use with an implanter tool and including a socket implant assembly including inner and outer implantable socket elements and a socket element mounting assembly adapted for preassembly with the inner and outer implantable socket elements. 
     There is even further provided in accordance with yet another preferred embodiment of the present invention a socket implanting assembly for use with an implanter tool and inner and outer implantable socket elements, the socket implanting assembly including a socket implant mounting assembly adapted for preassembly with the inner and outer implantable socket elements and for implanting operation in cooperation with the implanter tool. 
     Preferably, the implanter tool includes a central shaft extending along an axis and having an outer facing threaded portion adjacent the top thereof and a rotational driving assembly mounted onto the central shaft for driving rotation thereof, the rotational driving assembly including a handle fixed to the central shaft. Additionally, the central shaft is formed with an end portion having a reduced radius and defining a shoulder with respect to the remainder of the central shaft. Additionally, the end portion has an end surface formed with a bevel. 
     In another preferred embodiment, the socket implanting assembly also includes a sleeve disposed about the central shaft, the sleeve including a generally uniform inner surface and an inner facing threaded portion. Additionally, the sleeve includes an outer surface which includes a circumferential recess, defining a retaining circumferential protrusion which may be engaged by a protective sleeve, depending from the handle. Further, a central portion of the outer surface of the sleeve is knurled in order to provide a gripping surface for user engagement during implanting. 
     Preferably, the outer surface includes a peripheral protrusion of uniform radius and, spaced therefrom along the axis, a beveled protrusion, which tapers inwardly and towards a bottom edge of the sleeve, a space between the peripheral protrusion and the beveled protrusion defining a recess. Additionally or alternatively, the socket element mounting assembly is arranged for operational engagement with the central shaft and the sleeve. 
     Preferably, the socket element mounting assembly includes a flexible central element, a pair of outer elements and an end element. Additionally, the flexible central element is formed of a relatively rigid plastic material and is generally rotationally symmetric. Additionally, the flexible central element is formed with a generally flat top surface which surrounds a generally axial collar and is joined thereto by a beveled edge. Additionally, extending outwardly and downwardly from the top surface is an upper peripheral outer surface and extending downwardly from the upper peripheral outer surface is an intermediate peripheral outer surface which terminates in a peripheral recess and below the peripheral recess is a lower peripheral surface which terminates in a lower edge, there being provided, interiorly of the intermediate peripheral outer surface, the peripheral recess and the lower peripheral surface, an interior facing recess which defines an upper interior facing shoulder. 
     Preferably, a plurality of radially outward extending tabs are formed at a junction of the upper peripheral outer surface and the intermediate peripheral outer surface, and a plurality of slits are formed in the flexible central element to provide flexibility thereof and extend radially in evenly spaced azimuthal distribution through the flat top surface and the upper peripheral outer surface. 
     In another preferred embodiment, the socket implanting assembly also includes a bottom element formed with a central collar portion which is integrally joined at its bottom to a curved generally radially extending portion having a peripheral edge which is configured to seat in a recess of the flexible central portion against the upper interior facing shoulder. Additionally, a plurality of radially extending ribs are provided at the top of the radially extending portion and a ring integrally depends from the radially extending portion slightly inwardly of the peripheral edge, the ring defining a peripheral outwardly facing surface and an adjacent downwardly facing surface. 
     Preferably, the outer elements together define a generally hemispherical body and each include a generally flat top facing surface which defines a collar, an upper peripheral surface, an intermediate peripheral surface and a lower peripheral surface. 
     Preferably, apertures are formed in the intermediate peripheral surface to accommodate the tabs of the flexible central element for desired mounting of the outer elements with respect thereto. Additionally, the apertures each include a relatively widened portion for receiving one of the tabs and a relatively narrowed portion adjacent the widened portion for retaining the one of the tabs. 
     Preferably, the inner implantable socket element includes a relatively rigid implant element. Additionally, the inner implantable socket element includes a generally circular peripheral rim below which is defined a generally circular, peripheral, outer-facing recess and a generally spherical outer surface portion, the inner implantable socket element defining at an interior surface thereof, a generally spherical articulating surface. Additionally, the peripheral rim is formed with a beveled edge. 
     Preferably, the outer implantable socket element includes a relatively resilient implant element. Additionally, the outer implantable socket element includes a generally circular inwardly facing peripheral rim, which is adapted to be seated in the outer-facing recess of the inner implantable socket element, and, disposed below the circular inwardly facing peripheral rim, an inwardly tapered portion which terminates in an inwardly facing peripheral protrusion having a downwardly facing beveled edge adapted to engage the beveled edge of the inner implantable socket element. Additionally, the outer implantable socket element also includes, below the downwardly facing beveled edge, an inwardly facing recess which is adapted to engage the peripheral rim of the inner implantable socket element and below the inwardly facing recess, an inwardly facing protrusion which is adapted to engage the outwardly facing recess of the inner implantable socket element. 
     Preferably, the inwardly tapered portion of the outer implantable socket element lying below the inwardly facing peripheral protrusion is generally spherical and is adapted to engage the spherical outer surface portion of the inner implantable socket element and wherein an outer surface of the outer implantable socket element is generally spherical and includes a peripheral protrusion which lies intermediate therealong. Additionally, reinforcing material is provided at least one location between the inwardly tapered portion and the outer surface of the outer implantable socket element. Additionally, the reinforcing material is provided generally at a location which lies against a naturally occurring acetabulum notch in a patient&#39;s acetabulum. 
     Preferably, the inner implantable socket element includes a generally smooth outer surface which includes a circumferential protrusion intermediate therealong. Additionally, the outer implantable socket element includes a generally smooth outer surface and is adapted to be forced by the circumferential protrusion into locking engagement with a corresponding reamed recess formed in a patient&#39;s acetabulum. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of alleviating difficulties in joint articulation of a patient including placing a conformal, resilient element between respective articulating joint surfaces of the patient and retaining the conformal resilient element in a desired position with respect to the respective articulating joint surfaces by attachment thereof to patient tissue in the vicinity of the articulating joint surfaces. 
     There is further provided in accordance with yet another preferred embodiment of the present invention a method of implanting a bone implant element including a bone growth region, the method including the steps of positioning the bone implant element with the bone growth region in contact with a patient&#39;s bone surface, encouraging bone growth from the bone surface into the bone growth region and completing bone growth throughout the bone growth region, thereby locking the bone implant element to the bone surface within a few months. 
     There is still further provided in accordance with still another preferred embodiment of the present invention a method of implanting a bone implant element including at least one bone growth region and at least one drug delivery channel communicating therewith, the method including the steps of positioning the bone implant element with the at least one bone growth region in contact with a patient&#39;s bone surface, encouraging bone growth from the bone surface into the at least one bone growth region, effecting drug delivery through the at least one drug delivery channel to the bone surface and completing bone growth throughout the at least one bone growth region, thereby locking the bone implant element to the bone surface. 
     There is yet further provided in accordance with a further preferred embodiment of the present invention a method of implanting a bone splint implant element including at least two bone growth regions, the method including the steps of positioning the bone splint implant element with at least one of the at least two bone growth regions in contact with bone surfaces of each of at least two bone elements, encouraging bone growth from each of the bone surfaces into the at least two bone growth regions and completing bone growth throughout the at least two bone growth regions, thereby locking the bone splint implant element to the bone surfaces. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting a ligament attachment assembly including at least one bone growth region, the method including the steps of forming a hole in a bone in a manner providing a circumferential undercut, having a first circumferential surface and therebelow a second circumferential surface which are joined to define the circumferential undercut, providing the ligament attachment assembly, including a plurality of ligament attachment elements, each having looped therearound, at a ligament loop retaining location thereof, a closed looped ligament end and inserting the ligament attachment assembly into the hole and locating the plurality of ligament attachment elements in bone growth communication with a bone surface defined by the hole and configured such that bone growth thereat creates a grown bone ligament anchor binding the plurality of ligament attachment elements to the bone. 
     Preferably, the ligament attachment assembly includes a ligament attachment element positioner in the form of an elongate element having a generally conical surface at an inner end thereof, and the method also includes the steps of orienting the ligament attachment element positioner in a first operative orientation where the generally conical surface is generally decoupled from the plurality of ligament attachment elements and allows the plurality of ligament attachment elements to lie at a relatively radially inward position for insertion into the hole and thereafter orienting the ligament attachment element positioner in a second operative orientation where the generally conical surface engages inner surfaces of the plurality of ligament attachment elements, forces the plurality of ligament attachment elements radially outwardly such that respective first surfaces of the plurality of ligament attachment elements engage the first circumferential surface of the circumferential undercut and respective second surfaces of the plurality of ligament attachment elements engage the second circumferential surface of the circumferential undercut. 
     Additionally, the method of implanting a ligament attachment assembly also includes following the inserting and the orienting the ligament attachment element positioner in the second operative orientation, allowing bone growth to take place while the plurality of ligament attachment elements are retained such that the first respective surfaces of the plurality of ligament attachment elements engage the first circumferential surface of the circumferential undercut and the second respective surfaces of the plurality of ligament attachment elements engage the second circumferential surface of the circumferential undercut, thereby providing a grown bone lock binding the plurality of ligament attachment elements to the bone, thus creating the grown bone ligament anchor. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting an inter-surface articulating joint implant, the method including the steps of surgically inserting the inter-surface articulating joint implant between an acetabulum socket and a femoral head when the inter-surface articulating joint implant does not necessarily conform to corresponding shapes of articulating surfaces of the acetabulum socket and the femoral head, by means of at least some articulation of the hip joint, causing the shape of the inter-surface articulating joint implant to become increasingly conformal to the corresponding shapes of the articulating surfaces of the acetabulum socket and the femoral head and causing the inter-surface articulating joint implant to float in synovial fluid between the articulating surfaces of the acetabulum socket and the femoral head. 
     There is further provided in accordance with still another preferred embodiment of the present invention a method of implanting an inter-surface articulating joint implant, the method including the steps of surgically inserting the inter-surface articulating joint implant between an acetabulum socket and a femoral head when the inter-surface articulating joint implant does not necessarily conform to corresponding shapes of articulating surfaces of the acetabulum socket and the femoral head, by means of at least some articulation of the hip joint, causing the shape of the inter-surface articulating joint implant to become increasingly conformal to the corresponding shapes of the articulating surfaces of the acetabulum socket and the femoral head and causing the inter-surface articulating joint implant to partially float in synovial fluid between the articulating surfaces of the acetabulum socket and the femoral head and to partially contact at least one of the acetabulum socket and the femoral head. 
     Preferably, the method of implanting an inter-surface articulating joint implant also includes providing synovial fluid communication between a first synovial fluid region defined between the inter-surface articulating joint implant and the acetabulum socket and a second synovial fluid region defined between the inter-surface articulating joint implant and the femoral head. Additionally, the method of implanting an inter-surface articulating joint implant also includes pumping synovial fluid and thus providing micro-rotation of the inter-surface articulating joint implant relative to the acetabulum socket, thereby to tend to prevent the inter-surface articulating joint from being frozen in position relative to either of the articulating surfaces of the acetabulum socket and the femoral head and to contribute to lowering friction between the inter-surface articulating joint implant and the articulating surfaces of the acetabulum socket and the femoral head. 
     There is still further provided in accordance with yet another preferred embodiment of the present invention a method of implanting an inter-surface articulating joint implant, the method including the steps of surgically inserting the inter-surface articulating joint implant between a tibia and a femur head when the inter-surface articulating joint implant does not necessarily conform to corresponding shapes of articulating surfaces of the tibia and the femur head, by means of at least some articulation of the knee joint, causing the shape of the inter-surface articulating joint implant to become increasingly conformal to the corresponding shapes of the articulating surfaces of the tibia and the femur head and causing the inter-surface articulating joint implant to float in synovial fluid between the articulating surfaces of the tibia and the femur head. 
     There is even further provided in accordance with yet another preferred embodiment of the present invention a method of implanting an inter-surface articulating joint implant, the method including the steps of surgically inserting the inter-surface articulating joint implant between a tibia and a femur when the inter-surface articulating joint implant does not necessarily conform to corresponding shapes of articulating surfaces of the tibia and the femur, by means of at least some articulation of the knee joint, causing the shape of the inter-surface articulating joint implant to become increasingly conformal to the corresponding shapes of the articulating surfaces of the tibia and the femur and causing the inter-surface articulating joint implant to partially float in synovial fluid between the articulating surfaces of the tibia and the femur and to partially contact at least one of the tibia and the femur. 
     Preferably, the method of implanting an inter-surface articulating joint implant also includes providing synovial fluid communication between a first synovial fluid region defined between the inter-surface articulating joint implant and the tibia and a second synovial fluid region defined between the inter-surface articulating joint implant and the femur. Additionally, the method of implanting an inter-surface articulating joint implant also includes pumping synovial fluid, thereby to contribute to lowering friction between the inter-surface articulating joint implant and the articulating surfaces of the tibia and the femur. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting a meniscus implant, the method including the steps of surgically inserting the meniscus implant between a tibia and a femur when the meniscus implant does not necessarily conform to corresponding shapes of articulating surfaces of the tibia and the femur, by means of at least some articulation of the knee joint, causing the shape of the meniscus implant to become increasingly conformal to the corresponding shapes of the articulating surfaces of the tibia and the femur and causing the meniscus implant to float in synovial fluid between the articulating surfaces of the tibia and the femur. 
     There is further provided in accordance with yet another preferred embodiment of the present invention a method of implanting a meniscus implant, the method including the steps of surgically inserting the meniscus implant between a tibia and a femur when the meniscus implant does not necessarily conform to corresponding shapes of articulating surfaces of the tibia and the femur, by means of at least some articulation of the knee joint, causing the shape of the meniscus implant to become increasingly conformal to the corresponding shapes of the articulating surfaces of the tibia and the femur and causing the meniscus implant to partially float in synovial fluid between the articulating surfaces of the tibia and the femur and to partially contact at least one of the tibia and the femur. 
     Preferably, the method of implanting a meniscus implant also includes providing synovial fluid communication between a first synovial fluid region defined between the meniscus implant and the tibia and a second synovial fluid region defined between the meniscus implant and the femur. Additionally, the method of implanting a meniscus implant also includes pumping synovial fluid, thereby to contribute to lowering friction between the meniscus implant and the articulating surfaces of the tibia and the femur. 
     There is still further provided in accordance with still another preferred embodiment of the present invention a method of employing a shock-absorbing ball implant, the method including the steps of surgically inserting the shock-absorbing ball implant and rigidly mounting it onto a stem, disposing the shock-absorbing ball implant with an articulating surface thereof in articulating engagement with a socket and by walking or running, intermittently applying a force on the shock-absorbing ball implant via the socket, thereby producing deformation of the shock-absorbing ball implant and consequent temporary reshaping of the articulating surface, the deformation producing pumping of synovial fluid into an articulation region between the articulating surface and the socket. 
     Preferably, the method of employing a shock-absorbing ball implant also includes the step of by walking or running intermittently removing the force, thereby eliminating the deformation of the shock-absorbing ball implant and consequent temporary reshaping of the articulating surface and allowing drainage of the synovial fluid from the articulation region between the articulating surface and the socket. 
     There is yet further provided in accordance with yet another preferred embodiment of the present invention a method of employing an individually in-situ sizable ball implant, the method including the steps of surgically inserting the individually in-situ sizable ball implant and rigidly mounting it onto a stem, disposing the individually in-situ sizable ball implant with an articulating surface thereof in articulating engagement with a socket and selectably filling at least a portion of the individually in-situ sizable ball implant to cause the articulating surface to have an individually preferred configuration adapted to the socket. 
     Preferably, the method of employing an individually in-situ sizable ball implant also includes enhancing regeneration of cartilage along the articulating surface by precise matching of the articulating surface and the socket. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of surgically reaming a bone socket including the steps of providing a reamer including a bone anchor assembly including a generally spherical bone engagement surface and a central shaft extending along a longitudinal axis, the central shaft having a first threaded portion thereon, a rotational driving assembly, mounted for rotation about the central shaft and including a first handle fixedly associated with an elongate hollow shaft, which is sized to rotationally accommodate the central shaft, the hollow shaft terminating in a rotational driving plate, a rotational and axial driving element, coupled for rotation together with the rotational driving plate, the rotational and axial driving element including a second threaded portion, which threadably engages the first threaded portion, the rotational driving plate being formed with a plurality of axially extending portions which extend into corresponding axially extending sockets formed in the rotational and axial driving element and a plurality of first slidable knife support channels and the rotational and axial driving element being formed with a plurality of correspondingly positioned second slidable knife support channels, which extend generally at an angle with respect to the first slidable knife support channels and a plurality of knives, each slidably seated in a pair of corresponding ones of the first and second slidable knife support channels and mounted on a resilient knife support which permits simultaneous radially outward and rotational displacement of the plurality of knives in response to simultaneous axial and rotational movement of the rotational and axial driving element in threaded engagement with the first threaded portion in response to rotation of the first handle, placing the reamer with the bone anchor assembly in a bone socket to be reamed, pushing the first handle axially, thereby causing the generally spherical bone engagement surface to engage a bone surface at the bone socket, thereby anchoring the bone anchor assembly against rotation with respect to the bone socket, producing engagement of radial bone engagement tooth portions of the bone anchor assembly with side surfaces of the bone socket and rotating the first handle about the longitudinal axis, thereby causing rotation of the rotational and axial driving element about the longitudinal axis and consequent corresponding axially forward displacement of the rotational and axial driving element due to threaded engagement of the threaded portion the central shaft with the second threaded portion, the forward displacement driving the plurality of knives which are slidably seated in the first and second slidable knife support channels in a radially outward direction into cutting engagement with the bone socket and the rotation of the first handle about the longitudinal axis causing rotation of the rotational and axial driving element about the longitudinal axis and consequent corresponding axially forward displacement thereof, driving the plurality of knives into cutting engagement with the bone socket, thus producing a circumferential channel therein. 
     There is further provided in accordance with still another preferred embodiment of the present invention a method for assembly of a socket implant assembly, the method including the steps of mounting a flexible central element on an assembly fixture in a manner preventing relative rotation between the flexible central element and the assembly fixture, mounting a bottom element onto the flexible central element, mounting an inner implant element onto the flexible central element and the bottom element, mounting an outer implant element over the inner implant element and in engagement with the flexible central element and mounting outer elements onto the flexible central element. 
     There is yet further provided in accordance with yet another preferred embodiment of the present invention a method for mounting a socket implant assembly onto an implanter including the steps of providing the socket implant assembly including a flexible central element, a bottom element, an inner implant element, an outer implant element and outer elements, providing the implanter including a central shaft extending along an axis and having an outer facing threaded portion and an end portion having a reduced radius and defining a shoulder with respect to the remainder of the central shaft, the end portion having an end surface formed with a bevel, a rotational driving assembly mounted onto the central shaft for driving rotation thereof, the rotational driving assembly including a handle fixed to the central shaft and a sleeve disposed about the central shaft, the sleeve including a generally uniform inner surface, an inner facing threaded portion and an outer surface which is conditioned to provide a gripping surface for user engagement during implanting, the outer surface including a peripheral protrusion of uniform radius and spaced therefrom along the axis a beveled protrusion, which tapers inwardly and towards a bottom edge of the sleeve, a space being provided between the peripheral protrusion and the beveled protrusion and defining a recess and providing relative axial displacement of the socket implant assembly and the implanter along the axis, producing snap-fit engagement therebetween. 
     There is also provided in accordance with another preferred embodiment of the present invention a method for implanting a socket implant, the method including the steps of reaming a bone socket of a patient in order to define a circumferential groove therein, axially inserting a relatively resilient outer implant element into the bone socket and producing snap fit engagement of at least one circumferential protrusion of the relatively resilient outer implant element with the circumferential groove and axially producing engagement of a relatively rigid inner implant element with the outer implant element, thereby to retain the outer implant element in engagement with the bone socket. 
     Preferably, the method for implanting a socket implant also includes the steps of providing a socket implant assembly including a flexible central element, a bottom element, the inner implant element, the outer implant element and outer elements and employing the socket implant assembly in the axially inserting and the axially producing steps. 
     Additionally, the method for implanting a socket implant also includes the steps of providing an implanter including a central shaft extending along an axis and having an outer facing threaded portion and an end portion having a reduced radius and defining a shoulder with respect to the remainder of the central shaft, the end portion having an end surface formed with a bevel, a rotational driving assembly mounted onto the central shaft for driving rotation thereof, the rotational driving assembly including a handle fixed to the central shaft and a sleeve disposed about the central shaft, the sleeve including a generally uniform inner surface, an inner facing threaded portion and an outer surface which is conditioned to provide a gripping surface for user engagement during implanting, the outer surface including a peripheral protrusion of uniform radius and spaced therefrom along the axis a beveled protrusion, which tapers inwardly and towards a bottom edge of the sleeve, a space being provided between the peripheral protrusion and the beveled protrusion and defining a recess and employing the implanter for carrying out the axially inserting and the axially producing steps. 
     Additionally, the method for implanting a socket implant also includes the steps of rotation of the handle about the axis while the sleeve is held static, thus producing axial displacement of the central shaft relative to the sleeve, due to threaded engagement therebetween, and thus relative to the flexible central element, the axial displacement causing displacement of the bottom element and the inner implant element relative to the flexible central element and engagement of an outer surface of the inner implant element with a protrusion of the outer implant element, producing a slight deformation of the at least one circumferential protrusion, preliminary to the engagement between the inner implant element and the outer implant element. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting an orthopedic implant including attaching an implant element to at least one bone, the implant element including at least one throughgoing bone growth region adapted to be located in bone growth communication with the at least one bone and enhancing bone growth in the bone growth region such that the bone growth therein creates a grown bone suture binding the implant element to the at least one bone. 
     There is further provided in accordance with yet another preferred embodiment of the present invention a method of implanting an orthopedic implant including attaching a resilient implant element to at least one bone, the resilient implant element including at least one bone growth region adapted to be located in bone growth communication with the at least one bone and allowing bone growth in the at least one bone growth region such that the bone growth therein creates a grown bone lock binding the resilient implant element to the at least one bone. 
     There is yet further provided in accordance with still another preferred embodiment of the present invention a method of implanting an orthopedic implant including attaching an implant element to at least one bone, the implant element including at least one bone growth region adapted to be located in bone growth communication with the at least one bone and containing grown bone enhancing material and allowing bone growth in the at least one bone growth region such that bone growth therein creates a grown bone lock binding the implant element to the at least one bone. 
     Preferably, the grown bone enhancing material includes bone growth enhancing material and enhances the bone growth. Alternatively, the grown bone enhancing material includes grown bone reinforcing material which is operative to strengthen the grown bone lock. Additionally or alternatively, the at least one bone growth region contains a resorbable grown bone enhancing material which enhances bone growth. 
     Preferably, the at least one bone growth region also includes at least one drug supply channel and the method also includes supplying a drug via the at least one drug supply channel to at least one location on the at least one bone. 
     Preferably, the implant element is a grown bone locked splint implant and includes a plurality of throughgoing bone growth regions adapted to be located in bone growth communication with portions of the at least one bone such that bone growth therein creates a grown bone suture binding the grown bone locked splint implant to the portions of the at least one bone. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting an orthopedic implant including attaching a ligament attachment assembly to at least one bone and at least one ligament, the ligament attachment assembly including at least one ligament attachment element having at least one throughgoing bone growth region adapted to be located in bone growth communication with the at least one bone and encouraging bone growth in the at least one bone growth region thereby to create a grown bone suture binding the at least one ligament attachment element to the at least one bone. 
     There is further provided in accordance with still another preferred embodiment of the present invention a method of implanting an orthopedic implant including attaching a ligament attachment assembly to at least one bone, the ligament attachment assembly including at least one ligament attachment element having at least one bone growth region adapted to be located in bone growth communication with the at least one bone and enhancing bone growth in the at least one bone growth region, thereby creating a grown bone lock binding the at least one ligament attachment element to the at least one bone. 
     There is still further provided in accordance with yet another preferred embodiment of the present invention a method of implanting an orthopedic implant including attaching a ligament attachment assembly to at least one bone, the ligament attachment assembly including at least one ligament attachment element having at least one bone growth region adapted to be located in bone growth communication with the at least one bone and containing grown bone enhancing material and allowing bone growth in the at least one bone growth region to create a grown bone lock binding the at least one ligament attachment element to the at least one bone. 
     Preferably, the ligament attachment assembly includes multiple ligament attachment elements and a ligament attachment element positioner, which includes an elongate element formed with a generally conical surface at an inner end thereof, and the method also includes initially orienting the ligament attachment element positioner in a first operative orientation where the generally conical surface is generally decoupled from the multiple ligament attachment elements and allows the multiple ligament attachment elements to lie at a relatively radially inward position for insertion into a hole formed in the at least one bone and thereafter orienting the ligament attachment element positioner in a second operative orientation where the generally conical surface engages inner surfaces of the multiple ligament attachment elements and forces the multiple ligament attachment elements radially outwardly such that respective first surfaces of the multiple ligament attachment elements engage a first circumferential bone surface of an undercut formed in the at least one bone and respective second surfaces of the multiple ligament attachment elements engage a second circumferential bone surface of the undercut. 
     Additionally, following insertion of the ligament attachment assembly and the orienting the ligament attachment element positioner in the second operative orientation, bone growth is allowed to take place while the multiple ligament attachment elements are retained such that the respective first surfaces of the multiple ligament attachment elements engage the first circumferential bone surface of the undercut and the respective second surfaces of the multiple ligament attachment elements engage the second circumferential bone surface of the undercut. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting an orthopedic implant including inserting a conformal, resilient element between respective articulating joint surfaces of a patient, the conformal resilient element including at least one position maintaining engagement portion and attaching the at least one position maintaining engagement portion to patient tissue in the vicinity of the articulating joint surfaces. 
     Preferably, the conformal, resilient element is formed with at least one throughgoing channel and synovial fluid is pumped therethrough by changes in fluid pressure resulting from joint articulation and the application of changing forces to a joint. Additionally or alternatively, the conformal, resilient element is operative to enhance desired cartilage regeneration along at least one of the articulating joint surfaces. Alternatively or additionally, the conformal, resilient element is a generally cup-shaped element having an outer facing circumferential protrusion and is loosely seated in a corresponding recess in a surgically reamed socket, with synovial fluid being interposed between the cup-shaped element and the surgically reamed socket and between the cup-shaped element and a corresponding ball. 
     Preferably, the conformal resilient element is formed with throughgoing respective non-inclined and inclined passageways to allow synovial fluid to pass therethrough and with a relatively thin and highly resilient membrane portion and wherein the membrane functions as a synovial fluid pump in response to articulation of the articulating joint surfaces and variations in synovial fluid pressure thereat, thereby enhancing synovial fluid flow through the passageways and reducing friction between the articulating joint surfaces. 
     Preferably, immediately following surgical insertion thereof, the shape of the conformal resilient element does not necessarily conform to corresponding shapes of the articulating joint surfaces and following at least some articulation of the articulating joint surfaces, the shape of the conformal resilient element increasingly conforms to the corresponding shapes of the articulating joint surfaces. Additionally or alternatively, conformal, resilient element is operative during steady-state, long term use to float in synovial fluid between the articulating joint surfaces. Alternatively or additionally, the conformal, resilient element is operative during steady-state, long term use to partially float in synovial fluid between the articulating joint surfaces and to partially contact at least one of the articulating joint surfaces. 
     Preferably, the conformal, resilient element includes at least one inclined passageway, which provides synovial fluid communication between a first synovial fluid region defined between the conformal, resilient element and a surgically reamed socket and a second synovial fluid region defined between the conformal, resilient element and a corresponding ball. Additionally or alternatively, the conformal, resilient element includes at least one membrane portion defining a synovial fluid pump operative to cause micro-rotation of the conformal, resilient element relative to a socket. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting an orthopedic implant including inserting a resilient, at least partially hollow, meniscus implant element between respective articulating knee joint surfaces of a knee joint of a patient, the resilient meniscus implant element including at least one position maintaining engagement portion and attaching the at least one position maintaining engagement portion to patient tissue in the vicinity of the articulating knee joint surfaces. 
     Preferably, the meniscus implant element is formed with at least one throughgoing channel and synovial fluid is pumped therethrough by changes in fluid pressure resulting from knee joint articulation and the application of changing forces to a knee joint. Additionally or alternatively, the meniscus implant element is operative to enhance desired cartilage regeneration along at least one of the articulating knee joint surfaces. 
     Preferably, the meniscus implant element is a generally cup-shaped element having an outer facing circumferential protrusion and is loosely seated in a corresponding recess in a surgically reamed socket, with synovial fluid being interposed between the cup-shaped element and the surgically reamed socket and between the cup-shaped element and a corresponding ball. Additionally or alternatively, the meniscus implant element is formed with throughgoing respective non-inclined and inclined passageways to allow synovial fluid to pass therethrough and a relatively thin and highly resilient membrane portion and wherein the membrane functions as a synovial fluid pump in response to articulation of the articulating knee joint surfaces and variations in synovial fluid pressure thereat, thereby enhancing synovial fluid flow through the passageways and reducing friction between the articulating knee joint surfaces. 
     Preferably, immediately following surgical insertion thereof, the shape of the meniscus implant element does not necessarily conform to corresponding shapes of the articulating knee joint surfaces and following at least some articulation of the articulating knee joint surfaces, the shape of the meniscus implant element increasingly conforms to the corresponding shapes of the articulating knee joint surfaces. Additionally or alternatively, the meniscus implant element is operative during steady-state, long term use to float in synovial fluid between the articulating knee joint surfaces. Alternatively or additionally, the meniscus implant element is operative during steady-state, long term use to partially float in synovial fluid between the articulating knee joint surfaces and to partially contact at least one of the articulating knee joint surfaces. Alternatively or additionally, the meniscus implant element includes at least one inclined passageway, which provides synovial fluid communication between a first synovial fluid region defined between the meniscus implant element and a surgically reamed socket and a second synovial fluid region defined between the meniscus implant element and a corresponding ball. 
     There is also provided in accordance with another preferred embodiment of the present invention a method of implanting an orthopedic implant including mounting onto a stem, a shock-absorbing ball assembly including a stem mounting portion and a multi-layer shock-absorbing, ball-defining portion defining a generally ball-shaped articulating surface. 
     Preferably, the shock-absorbing ball assembly is formed with at least one throughgoing channel and synovial fluid passes therethrough in response to changes in fluid pressure resulting from joint articulation and the application of changing forces to a joint. Additionally or alternatively, the shock-absorbing ball assembly is configurable in situ to provide an individualized fit with a socket. Alternatively or additionally, the shock-absorbing ball assembly enhances desired cartilage regeneration along an articulating surface of a socket. 
     Preferably, the shock-absorbing ball assembly includes a replacement socket having an outer facing rim, a generally ball shaped hollow element fixed to the stem and defining an articulating surface, at least one relatively thin reinforcing layer; a core element, disposed within the hollow element and separated therefrom by the at least one relatively thin reinforcing layer, the core element being formed with at least one synovial fluid void and at least one first synovial fluid communication passageway which communicates with the at least one synovial fluid void and a location adjacent the outer facing rim and formed with at least one second synovial fluid communication passageway which communicates between the at least one synovial fluid void through the core element, the at least one reinforcing layer and the hollow element with the articulating surface, thus providing synovial fluid communication with the articulating surface and at least one one-way flow valve associated with at least one of the first and second synovial fluid communication passageways; and the method also includes pumping, produced by articulation of the shock-absorbing ball assembly relative to the socket, which causes a relatively large amount of synovial fluid to be provided in an articulation region between the articulating surface of the shock-absorbing ball assembly and a corresponding articulating surface of the socket. 
     Additionally, the pumping is constrained by the at least one one-way flow valve such that synovial fluid flows towards the at least one synovial fluid void only via the at least one first synovial fluid communication passageway and from the at least one synovial fluid void to the articulation region only via the at least one second synovial fluid communication passageway. 
     Preferably, the method of implanting an orthopedic implant also includes providing at least one selectably inflatable, selectably expandable void located so as to underlie most of a generally spherical articulating surface defined by the shock-absorbing ball assembly and a spherical radius determining material passageway communicating with the selectably inflatable void and selectably inserting a spherical radius determining material into the selectably inflatable void in order to enable adaptation of the overall radius of the generally spherical articulating surface in situ so as to provide individualized fit of the shock-absorbing ball assembly to a patient&#39;s socket. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will be understood and appreciated more fully from the following detailed description, taken in conjunction with the drawings in which: 
         FIG. 1  is a simplified anatomical illustration showing various applications of a grown bone locked implant constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIGS. 2A &amp; 2B  are simplified partial illustrations of a plurality of alternative structures of a grown bone lockable implant useful in the embodiment of  FIG. 1 ; 
         FIGS. 3A &amp; 3B  are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 2A &amp; 2B ; 
         FIG. 4  is a simplified partial illustration of an alternative embodiment of another grown bone lockable implant useful in the embodiment of  FIG. 1 ; 
         FIG. 5  is a simplified illustration of sequential bone growth and medicament dispersal in the embodiment illustrated  FIG. 4 ; 
         FIG. 6  is a simplified anatomical illustration showing various applications of a grown bone locked splint implant constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIGS. 7A &amp; 7B  are simplified partial illustrations of a plurality of alternative structures of a grown bone lockable implant useful in the embodiment of  FIG. 6 ; 
         FIGS. 8A &amp; 8B  are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 7A &amp; 7B ; 
         FIG. 9  is a simplified anatomical illustration showing various applications of a grown bone locked ligament attachment implant constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIG. 10  is a simplified illustration of steps in the insertion of the ligament attachment implant of  FIG. 9  into a bone; 
         FIGS. 11A &amp; 11B  are simplified partial illustrations of a plurality of alternative structures of a grown bone lockable implant useful in the embodiment of  FIG. 9 ; 
         FIGS. 12A &amp; 12B  are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 11A &amp; 11B ; 
         FIG. 13  is a simplified anatomical illustration showing various applications of an inter-surface articulating joint implant constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIGS. 14A &amp; 14B  are simplified partial illustrations of a plurality of alternative structures of an inter-surface articulating joint implant useful in the embodiment of  FIG. 13 ; 
         FIGS. 15A &amp; 15B  are simplified illustrations of an aspect of the functionality of the inter-surface articulating joint implant in the embodiments illustrated respectively in  FIGS. 14A &amp; 14B ; 
         FIGS. 16A &amp; 16B  are simplified partial illustrations of a plurality of alternative structures of another inter-surface articulating joint implant useful in the embodiment of  FIG. 13 ; 
         FIGS. 17A &amp; 17B  are simplified illustrations of an aspect of the functionality of the inter-surface articulating joint implants in the embodiments illustrated respectively in  FIGS. 16A &amp; 16B ; 
         FIG. 18  is a simplified anatomical illustration showing various applications of a meniscus implant constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIGS. 19A &amp; 19B  are simplified partial illustrations of a plurality of alternative structures of a meniscus implant useful in the embodiment of  FIG. 18 ; 
         FIGS. 20A &amp; 20B  are simplified illustrations of an aspect of the functionality of the meniscus implant in the embodiments illustrated respectively in  FIGS. 19A &amp; 19B ; 
         FIGS. 21A ,  21 B,  21 C and  21 D are sectional illustrations of a plurality of alternative constructions of the meniscus implant of  FIGS. 18-20B , taken along the lines XXI-XXI in  FIG. 18 ; 
         FIG. 22  is a simplified anatomical illustration showing various applications of a ball implant constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIGS. 23A ,  23 B and  23 C are simplified partial illustrations of a plurality of alternative structures of a ball implant useful in the embodiment of  FIG. 22 ; 
         FIGS. 24A &amp; 24B  are simplified illustrations of aspects of the functionality of the ball implants in the embodiments illustrated respectively in  FIGS. 22A &amp; 22B ; 
         FIG. 25  is a simplified pictorial illustration of a groove reamer constructed and operative in accordance with a preferred embodiment of the present invention, useful, for example in the embodiment of  FIG. 13 ; 
         FIG. 26  is a simplified composite illustration showing the structure of the groove reamer of  FIG. 25 ; 
         FIGS. 27A ,  27 B,  27 C and  27 D are simplified sectional illustrations illustrating various stages of the operation of the groove reamer of  FIGS. 25 and 26 ; 
         FIG. 28  is a simplified composite exploded-view illustration of a socket implant assembly and implanter useful therewith, constructed and operative in accordance with a preferred embodiment of the present invention; 
         FIG. 29  is a simplified sectional assembled-view illustration of the socket implant assembly and implanter of  FIG. 28 ; 
         FIGS. 30A ,  30 B,  30 C,  30 D,  30 E and  30 F are simplified illustrations of assembly of the socket implant assembly of  FIGS. 28 and 29 ; 
         FIGS. 31A ,  31 B and  31 C are simplified illustrations of mounting of a socket implant assembly onto an assembler; 
         FIGS. 32A ,  32 B,  32 C and  32 D are simplified illustrations of implanting a socket implant employing the apparatus of  FIGS. 28 and 29 ; 
         FIG. 33  is a simplified composite exploded-view illustration of a socket implant assembly and implanter useful therewith, constructed and operative in accordance with another preferred embodiment of the present invention; and 
         FIG. 34  is a simplified illustration of a final stage of implanting the socket implant assembly of  FIG. 33  into a patient. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     Reference is now made to  FIGS. 1-3B  which illustrate various applications of a grown bone locked implant constructed and operative in accordance with a preferred embodiment of the present invention. 
     There is provided in accordance with a preferred embodiment of the present invention an orthopedic implant including an implant element adapted to be attached to at least one bone, the implant element including at least one throughgoing bone growth region adapted to be located in bone growth communication with the bone and configured such that bone growth therein creates a grown bone suture binding the implant element to the bone. 
     Additionally or alternatively, the implant element may be resilient and be adapted to be attached to at least one bone and may include at least one bone growth region adapted to be located in bone growth communication with the bone and configured such that bone growth therein creates a grown bone lock binding the resilient implant element to the bone. 
     Additionally or alternatively, the implant element may be adapted to be attached to at least one bone, the implant element including at least one bone growth region adapted to be located in bone growth communication with the at least one bone and containing grown bone enhancing material configured such that bone growth therein creates a grown bone lock binding the implant element to the bone. 
     The grown bone enhancing material preferably comprises bone growth enhancing material and/or grown bone reinforcing material. 
     Turning initially to  FIG. 1 , there is provided a simplified anatomical illustration showing various applications of a grown bone locked implant of the type described hereinabove, constructed and operative in accordance with a preferred embodiment of the present invention. A shoulder joint implant assembly, shown in an enlargement designated by reference numeral  102 , includes a grown bone locked artificial glenoid socket element  104  which is constructed and operative in accordance with a preferred embodiment of the present invention. 
     An elbow joint implant assembly, shown in an enlargement designated by reference numeral  106 , includes grown bone locked implant elements  108  and  110 , which are constructed and operative in accordance with a preferred embodiment of the present invention. 
     A hip joint implant assembly, shown in an enlargement designated by reference numeral  112 , includes a grown bone locked implant element  114  which is constructed and operative in accordance with a preferred embodiment of the present invention. 
     A knee joint implant assembly, shown in an enlargement designated by reference numeral  116 , includes a grown bone locked implant element  118  which is constructed and operative in accordance with a preferred embodiment of the present invention. 
     A disc replacement implant assembly, shown in successive enlargements designated by reference numerals  120 ,  122  and  124 , includes a grown bone locked implant element  126  which is constructed and operative in accordance with a preferred embodiment of the present invention. Preferably, the grown bone locked implant element  126  includes a bone growth region  130  which is preferably throughgoing and which is preferably in the shape of a hook or a handle, as shown. 
     Specific reference is now made to  FIGS. 2A &amp; 2B , which are simplified partial illustrations of a plurality of alternative structures of grown bone lockable implant useful in the embodiment of  FIG. 1  and to  FIGS. 3A &amp; 3B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 2A &amp; 2B . 
       FIGS. 2A &amp; 2B  represent two alternative embodiments of an exemplary implant element useful in a disc replacement implant assembly as shown in enlargement  124  of  FIG. 1 .  FIGS. 2A &amp; 2B  are pictorial illustrations of implant element  126  taken generally along lines II-II in enlargement  122 .  FIGS. 3A &amp; 3B  are sectional illustrations of implant element  126  taken generally along the lines II-II. It is appreciated that the descriptions of  FIGS. 2A-3B  which follow are applicable to any other suitable type of grown bone lockable implant. 
     Turning now to  FIGS. 2A &amp; 2B , there are seen partial illustrations of a portion of a grown bone lockable implant element, such as a replacement spinal disc.  FIG. 2A  shows a portion of the implant element  126  having formed therein bone growth region  130 , which is preferably throughgoing and preferably is in the shape of a hook or a handle. In accordance with a preferred embodiment of the present invention, bone growth region  130  is generally filled with a resorbable material such as any one of the following materials: 
     α-BSM, commercially available from Etex Corporation of 38 Sidney Street, Cambridge, Mass. 02139; 
     Bi-Ostetic, commercially available from Berkeley Advanced Biomaterials, Inc., of 901 Grayson St., Suite 101, Berkeley Calif. 94710; and 
     Boneplast™ Bone Void Filler, commercially available from Interpore Cross International, Inc. of 181 Technology Drive, Irvine, Calif. 92618. 
     Additionally or alternatively, bone growth region  130  is generally filled with a material, such as any one of the following materials: 
     a bone graft substitute such as Chronos Granules, commercially available from Synthes, Inc. of 1302 Wrights Lane East, West Chester, Pa. 19380 or POLYGRAFT BGS Technology Bone Graft Substitute, commercially available from OsteoBiologics, Inc. of 12500 Network, Suite 112, San Antonio, Tex. 78249; 
     a BMP material such as Infuse® Bone Graft, commercially available from Medtronic of 710 Medtronic Parkway Minneapolis, Minn. 55432-5604; 
     a parathyroid hormone such as Forteo, commercially available from Eli Lilly And Company of Lilly Corporate Center Indianapolis, Ind. 46285 USA; and 
     a Bisphosphonate material such as Fosamax (alendronate) Bone-strengthening drugs, commercially available from Merck &amp; Co., Inc. of One Merck Drive P.O. Box 100 Whitehouse Station, N.J. 08889-0100 USA. 
       FIG. 2B  shows a portion of the implant element  126  having formed therein a bone growth region  130 , which is preferably throughgoing and is preferably in the shape of a hook or a handle. In accordance with a preferred embodiment of the present invention, bone growth region  130  is generally filed with a resorbable material of the type described hereinabove with reference to  FIG. 2A . In addition, the implant element of  FIG. 2B  includes reinforcement elements  134 , preferably relatively rigid elongate metal elements or relatively flexible fibers, located in the bone growth region. 
     Turning now to  FIGS. 3A &amp; 3B , there are seen simplified illustrations of sequential bone growth in the embodiments illustrated in  FIGS. 2A &amp; 2B  respectively.  FIGS. 3A and 3B  each show at step A the implant element  126  positioned in contact with a vertebral endplate  140 . The bone growth region  130  is shown filled with one or more of the materials described hereinabove with reference to  FIGS. 2A and 2B . As seen in step A, bone growth has not yet commenced. At steps B and C respectively, initial and further bone growth from endplate  140  into bone growth region  130  are shown. Step D shows complete bone growth throughout the throughgoing bone growth region  130 . The entire bone growth process can be expected to take place over a period of a few months. 
     Reference is now made to  FIG. 4 , which is a simplified partial illustration of a grown bone lockable implant useful in the embodiment of  FIG. 1  and to  FIG. 5 , which is a simplified illustration of sequential bone growth and drug delivery in the embodiment illustrated  FIG. 4 . 
       FIG. 4  represents an exemplary implant element useful in a hip replacement implant assembly as shown in enlargement  112  of  FIG. 1 .  FIG. 4  is a pictorial illustration of implant element  114  taken generally along lines IV-IV in enlargement  112 .  FIG. 5  is a sectional illustration of implant element  114  taken generally along lines V-V in  FIG. 4 . It is appreciated that the descriptions of  FIGS. 4 and 5  which follow are applicable to any other suitable type of grown bone lockable implant. 
     Turning now to  FIG. 4 , there is seen a partial illustration of a portion of a grown bone lockable implant element, such as a replacement acetabulum.  FIG. 4  shows a portion of the implant element  114  having formed therein a bone growth region  150 , which is preferably throughgoing and is preferably in the shape of a hook or a handle. Forming part of or communicating with bone growth region  150  there are preferably provided one or more drug supply channels  152 , each preferably containing a drug, preferably in a timed-release dosage form, which it is sought to supply to one or more locations on an adjacent bone  154 . Some examples of timed release drugs include: 
     Taxanes such as Nolvadex (Tamoxifen Citrate) commercially available from Astrazeneca Pharmaceuticals Lp (U.S. Headquarters) of Wilmington, Mass.; 
     Alkylating agents such as Cytoxan and Neosar which are commercially available from Mead Johnson Oncology Products of Princeton, N.J.; 
     Anthracyclines such as Adriamycin and Ellence which are commercially available from Pharmacia &amp; Upjohn of 100 Rte. 206 North, Peapack, NJ 07977; and 
     Platinum compounds such as PLATINOL-AQ, commercially available from Bristol Myers-Squibb Company of Princeton, N.J. 08543. 
     In accordance with a preferred embodiment of the present invention, channels  152  and bone growth region  150  are generally filled with bone growth enhancing materials of the type described hereinabove with respect to  FIGS. 2A &amp; 2B . Channels  152  and other parts of the bone growth region  150  may be formed with an undercut, as shown, in order to enhance grown bone locking thereat. In accordance with an alternative embodiment of the present invention, the implant element containing drug supply channels  152  need not necessarily be a grown bone lockable implant. 
     Turning now to  FIG. 5 , there is seen a simplified illustration of sequential bone growth and drug delivery in the embodiment illustrated in  FIG. 4 .  FIG. 5  shows at step A, the implant element  114  positioned in contact with an acetabulum bone  154 . The bone growth region  150  and channels  152  are shown filled with one or more of the materials described hereinabove with reference to  FIGS. 2A and 2B . Channels  152  also include one or more drugs. As seen at step A, bone growth and drug delivery have not yet commenced. At steps B and C respectively, initial and further bone growth from acetabulum bone  154  into bone growth region  150  are shown at reference numeral  162  and drug delivery through channels  152  to bone  154  is shown at reference numeral  164 . Step D shows complete bone growth throughout the throughgoing bone growth region  150  and continuing drug delivery through channels  152 . The entire bone growth process can be expected to take place over a period of a few months and the drug delivery can take place over a shorter or longer period. 
     Reference is now made to  FIG. 6 , which is a simplified anatomical illustration showing various applications of a grown bone locked splint implant constructed and operative in accordance with a preferred embodiment of the present invention, to  FIGS. 7A &amp; 7B , which are simplified partial illustrations of a plurality of alternative structures of grown bone lockable implant useful in the embodiment of  FIG. 6 , and to  FIGS. 8A &amp; 8B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 7A &amp; 7B . 
     There is provided in accordance with a preferred embodiment of the present invention a splint implant including a splint implant element adapted to be attached to two portions of at least one bone, the implant element including a plurality of throughgoing bone growth regions adapted to be located in bone growth communication with the portions of the bone and configured such that bone growth therein creates a grown bone suture binding the implant element to the portions of the bone. 
     Additionally or alternatively, the splint implant element may be resilient and may be adapted to be attached to portions of a bone and may include a plurality of bone growth regions adapted to be located in bone growth communication with the portions of the bone and configured such that bone growth therein creates a grown bone lock binding the resilient implant element to the bone. 
     Additionally or alternatively, the splint implant element may be adapted to be attached to portions of a bone and may include a plurality of bone growth regions adapted to be located in bone growth communication with the bone portions and containing grown bone enhancing material configured such that bone growth therein creates a grown bone lock binding the splint implant element to the bone. 
     The grown bone enhancing material preferably comprises bone growth enhancing material and/or grown bone reinforcing material. 
     Turning initially to  FIG. 6 , there is provided a simplified anatomical illustration showing various applications of a grown bone locked splint implant of the type described hereinabove, constructed and operative in accordance with a preferred embodiment of the present invention. 
     A humerus splint implant assembly, shown in an enlargement designated by reference numeral  202 , includes a grown bone locked humerus splint implant element  204  which is constructed and operative in accordance with a preferred embodiment of the present invention and arranged to surround portions of the humerus. 
     A femur splint implant assembly, shown in an enlargement designated by reference numeral  206 , includes grown bone locked femur splint implant element  208 , constructed and operative in accordance with a preferred embodiment of the present invention. 
     A tibia splint implant assembly, shown in an enlargement designated by reference numeral  212 , includes a grown bone locked tibia splint implant element  214  constructed and operative in accordance with a preferred embodiment of the present invention. 
     Reference is now made to  FIGS. 7A &amp; 7B , which are simplified partial illustrations of a plurality of alternative structures of grown bone lockable splint implant useful in the embodiment of  FIG. 6  and to  FIGS. 8A &amp; 8B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 7A &amp; 7B . 
       FIGS. 7A &amp; 7B  represent two alternative embodiments of an exemplary implant element useful in a femur splint implant assembly as shown in enlargement  206  of  FIG. 6 .  FIGS. 7A &amp; 7B  are partially pictorial partially sectional illustrations of implant element  208  taken generally along lines VII-VII in enlargement  206 .  FIGS. 8A &amp; 8B  are sectional illustrations of implant element  208  taken generally along the lines VII-VII in enlargement  206 . It is appreciated that the descriptions of  FIGS. 7A-8B  which follow are applicable to any other suitable type of grown bone lockable implant. 
     Turning now to  FIGS. 7A &amp; 7B , there are seen partial illustrations of a portion of a grown bone lockable splint implant element  208 , such as a femur splint implant element.  FIG. 7A  shows a portion of the implant element  208  arranged to surround portions  216  and  218  ( FIG. 6 ) of an elongate bone, such as the femur. In the illustrated embodiment, the implant element is typically in the form of a split cylinder  220  formed of a somewhat resilient material, such as polyurethane, and is preferably formed with a plurality of elongate reinforcing strips  222 , typically formed of a generally non-stretchable material such as a composite material or metal, embedded therein. 
     In accordance with a preferred embodiment of the present invention, the split cylinder  220  has formed therein a plurality of bone growth regions  230 , which are preferably throughgoing, preferably are in the shape of a hook or a handle, and which preferably encircle one of the reinforcing strips  222  as shown. In accordance with a preferred embodiment of the present invention, bone growth regions  230  are generally filled with a resorbable material such as any one of the materials listed above with reference to  FIG. 2A . 
     Additionally or alternatively, bone growth regions  230  are generally filled with a material, such as any one of the materials listed hereinabove with reference to  FIGS. 2A &amp; 2B . 
       FIG. 7B  shows a portion of the implant element  208  having formed therein preferably throughgoing bone growth regions  230 , preferably in the shape of a hook or a handle, as shown. In accordance with a preferred embodiment of the present invention, bone growth regions  230  are generally filed with a resorbable material of the type described hereinabove with reference to  FIG. 7A . In addition, the splint implant element of  FIG. 7B  includes reinforcement elements  234 , preferably relatively rigid elongate metal elements or relatively flexible fibers located in the bone growth regions  230 , which preferably encircle a reinforcing strip  222 . 
     Reference is now made to  FIGS. 8A &amp; 8B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 7A &amp; 7B .  FIGS. 8A and 8B  each show at step A the implant element  208  positioned in contact with portions  216  and  218  ( FIG. 6 ) of an elongate bone, such as the femur. The bone growth regions  230  are shown filled with one or more of the materials described hereinabove with reference to  FIG. 2A . As seen in step A, bone growth has not yet commenced. At steps B and C respectively, initial and further bone growth from portions  216  and  218  ( FIG. 6 ) of the femur into bone growth regions  230  are shown. Step D shows complete bone growth throughout the throughgoing bone growth regions  230 . The entire bone growth process can be expected to take place over a period of a few months. 
     It is appreciated that the splint implant described hereinabove with reference to  FIGS. 6-8B  may be employed for broken elongated bones as well as for weakened bones, such as bones suffering from osteoporosis or bones weakened by cancer. 
     Reference is now made to  FIG. 9 , which is a simplified anatomical illustration showing various applications of a grown bone locked ligament attachment implant constructed and operative in accordance with a preferred embodiment of the present invention, to  FIG. 10 , which illustrates steps in the insertion of the ligament attachment implant, to  FIGS. 11A &amp; 11B  which are simplified partial illustrations of a plurality of alternative structures of grown bone lockable implant useful in the embodiment of  FIG. 9 , and to  FIGS. 12A &amp; 12B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 10A &amp; 10B . 
     There is provided in accordance with a preferred embodiment of the present invention a ligament attachment implant including a ligament attachment assembly comprising one or more ligament attachment elements adapted to be attached to a bone, each ligament attachment implant element adapted to be located in bone growth communication with a portion of the bone and configured such that bone growth therein creates a grown bone ligament anchor. Preferably, the ligament attachment elements contain grown bone enhancing material configured such that bone growth therein creates a grown bone lock binding the implant element to the bone. 
     The grown bone enhancing material preferably comprises bone growth enhancing material and/or grown bone reinforcing material. 
     Turning initially to  FIG. 9 , there is provided a simplified anatomical illustration showing various applications of a grown bone locked implant of the type described hereinabove, constructed and operative in accordance with a preferred embodiment of the present invention. 
     A knee ligament attachment assembly, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  302 . 
     A hip ligament attachment assembly, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  306 . 
     A shoulder ligament attachment assembly, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  312 . 
     Reference is now made to  FIG. 10 , which shows steps in the insertion of knee ligament attachment assembly in a tibia. It is appreciated that the hip and shoulder ligament attachment implant assemblies are similar in all relevant respects to the knee ligament attachment assembly shown in  FIGS. 10-12B . 
     Initially, as shown at A, a hole  318  is formed in the tibia  319  by conventional surgical drilling techniques. The hole  318  is characterized in that it has a circumferential undercut, indicated generally by reference numeral  320 . The undercut has a first circumferential surface  322  and therebelow a second circumferential surface  324 . Generally, surfaces  322  and  324  are smoothly joined to define the undercut  320 . 
     As seen at B, there is provided a knee ligament attachment assembly  328 , which preferably comprises a plurality of ligament attachment elements  330 , each having looped therearound, at a ligament loop retaining location  332  thereof, a closed looped ligament end  334 . The closed loop ligament ends  334  may be formed of natural or artificial ligaments or portions thereof. A single ligament may be formed with multiple ligament ends. Ligament attachment elements  330  are preferably formed of or include bone growth enhancement materials, such as those referenced hereinabove in connection with  FIG. 2A . In the illustrated embodiment, the knee ligament attachment assembly includes three ligament attachment elements  330 . 
     In accordance with a preferred embodiment of the invention, each ligament attachment element  330  is adapted to be located in bone growth communication with a bone surface and configured such that bone growth therein creates a grown bone ligament anchor. Preferably, the bone growth enhancing material in the ligament attachment elements creates a grown bone lock binding the ligament attachment element to the bone. 
     Knee ligament attachment assembly  328  also includes a ligament attachment element positioner  336 , preferably in the form of an elongate element formed with a generally conical surface  338  at an inner end thereof. Positioner  336  preferably has two operative orientations, a first, shown at B, where the generally conical surface is generally decoupled from attachment elements  330  and allows them to lie at a relatively radially inward position for insertion into hole  318 . 
     A second operative orientation of positioner  336 , shown at C, in which the generally conical surface  338  engages inner surfaces  340  of attachment elements  330 , forces the attachment elements radially outwardly such that respective surfaces  342  of attachment elements  330  engage first circumferential bone surface  322  of undercut  320  and respective surfaces  344  of attachment elements  330  engage second circumferential bone surface  324  of undercut  320 . 
     Following insertion of implant assembly  328  and positioning positioner  336  in its second operative orientation as shown at C, bone growth is allowed to take place while attachment elements  330  are retained such that respective surfaces  342  of attachment elements  330  engage first circumferential bone surface  322  of undercut  320  and respective surfaces  344  of attachment elements  330  engage second circumferential bone surface  324  of undercut  320 . 
     Preferably, the bone growth enhancing material in the ligament attachment elements  330  creates a grown bone lock binding the implant element to the bone, thus creating a grown bone ligament anchor in accordance with a preferred embodiment of the present invention. 
     Reference is now made to  FIGS. 11A &amp; 11B , which are simplified partial illustrations of two alternative structures of grown bone lockable ligament attachment implant useful in the embodiment of  FIG. 9  and to  FIGS. 12A &amp; 12B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 11A &amp; 11B . 
       FIGS. 11A &amp; 11B  illustrate a portion of an exemplary ligament attachment assembly  328  as shown in enlargement  302  of  FIG. 9 .  FIGS. 11A &amp; 11B  are pictorial illustrations of two alternative embodiments of ligament attachment assembly  328  taken generally along lines XI-XI in  FIG. 10 .  FIGS. 12A &amp; 12B  are sectional illustrations of ligament attachment assembly  328  taken generally along lines XII-XII in  FIG. 11A . It is appreciated that the descriptions of  FIGS. 11A-12B  which follow are applicable to any other suitable type of grown bone lockable implant. 
     Turning now to  FIGS. 11A &amp; 11B , there are seen partial illustrations of a portion of a grown bone lockable ligament attachment assembly  328 .  FIG. 11A  shows a portion of the ligament attachment assembly  328  with positioner  336  in its second operative orientation such that bone growth is allowed to take place while ligament attachment elements  330  are retained such that respective surfaces  342  of ligament attachment elements  330  engage first circumferential bone surface  322  of undercut  320  and respective surfaces  344  of ligament attachment elements  330  engage second circumferential bone surface  324  of undercut  320 . 
       FIG. 11B  shows a portion of the ligament attachment assembly  328  including ligament attachment elements which also include reinforcement elements  354 , preferably relatively rigid elongate metal elements or relatively flexible fibers. 
     Reference is now made to  FIGS. 12A &amp; 12B , which are simplified illustrations of sequential bone growth in the embodiments illustrated respectively in  FIGS. 11A &amp; 11B .  FIGS. 12A and 12B  each show at step A an ligament attachment element  330  positioned in contact with surface  322  of the tibia  319 . As seen in step A, bone growth has not yet commenced. At steps B and C respectively, initial and further bone growth from surface  322  of the tibia  319  into the ligament attachment element  330  are shown. Step D shows complete bone growth throughout the ligament attachment element  330 . The entire bone growth process can be expected to take place over a period of a few months. 
     Reference is now made to  FIG. 13 , which is a simplified anatomical illustration showing various applications of an inter-surface articulating joint implant constructed and operative in accordance with a preferred embodiment of the present invention, to  FIGS. 14A &amp; 14B , which are simplified partial illustrations of a plurality of alternative structures of an inter-surface articulating joint implant useful in the embodiment of  FIG. 13  and to  FIGS. 15A &amp; 15B , which are simplified illustrations of an aspect of the functionality of the inter-surface articulating joint implant in the embodiments illustrated respectively in  FIGS. 14A &amp; 14B . 
     There is provided in accordance with a preferred embodiment of the present invention an inter-surface articulating joint implant adapted to be located between articulating surfaces of a joint, the inter-surface articulating joint implant being a generally thin element formed of a flexible resilient material and being adapted to be generally surrounded by synovial fluid. 
     Preferably, the inter-surface articulating joint implant is formed with one or more throughgoing channels for passage of synovial fluid therethrough in response to changes in fluid pressure resulting from joint articulation and the application of changing forces to the joint. 
     The inter-surface articulating joint implant preferably serves to decrease or eliminate frictional engagement between the articulating surfaces of the joint. Additionally or alternatively, the inter-surface articulating joint implant may serve to enhance desired cartilage regeneration along one or both articulating surfaces of the joint. 
     Turning initially to  FIG. 13 , there is provided a simplified anatomical illustration showing various applications of an inter-surface articulating joint implant of the type described hereinabove, constructed and operative in accordance with a preferred embodiment of the present invention. 
     A shoulder inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  402 . 
     An elbow inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  404 . 
     A hip inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  406 . 
     A plurality of femur-patella/knee inter-surface articulating joint implants, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  408 . 
     A tibia/knee inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  409 . 
     Reference is now made to  FIGS. 14A &amp; 14B , which are simplified partial illustrations of a plurality of alternative structures of a hip inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 13  and to  FIGS. 15A &amp; 15B , which are simplified illustrations of operation of the inter-surface articulating joint implant in the embodiments illustrated respectively in  FIGS. 14A &amp; 14B . 
       FIGS. 14A &amp; 14B  represent two alternative embodiments of an hip inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 13 .  FIGS. 14A &amp; 14B  are pictorial illustrations of a hip inter-surface articulating joint implant  412 .  FIGS. 15A &amp; 15B  are sectional illustrations of hip inter-surface articulating joint implant  412 , taken generally along lines XVA-XVA in  FIG. 14A  and lines XVB-XVB in  FIG. 14B , respectively. It is appreciated that the descriptions of  FIGS. 14A-15B  which follow are applicable to any other suitable similar type of implant. 
     Turning now to  FIGS. 14A &amp; 14B , there are seen partial illustrations of a portion of hip inter-surface articulating joint implant  412 , constructed and operative in accordance with a preferred embodiment of the present invention.  FIG. 14A  shows the implant  412  as a generally cup-shaped element having an outer facing circumferential protrusion  416  arranged to be loosely seated in a corresponding recess  418  in a surgically reamed acetabulum socket  420 , with synovial fluid  421  being interposed between implant  412  and the surgically reamed acetabulum socket  420  and between implant  412  and a corresponding femoral head  422 . In the illustrated embodiment, the implant  412  is preferably formed of a somewhat resilient material, such as polyurethane. 
       FIG. 14B  shows a portion of an alternative embodiment of a hip inter-surface articulating joint implant, here designated by reference numeral  424 , the structure of which differs from the structure of implant  412  ( FIG. 14A ) in that throughgoing respective non-inclined and inclined passageways  426  and  427  are formed to allow synovial fluid  421  to pass through the implant and the implant is formed with a relatively thin and highly resilient membrane portion  428 , preferably arranged to be positioned at the eskelsis. The membrane portion preferably functions as a synovial fluid pump in response to articulation of the hip joint and variations in synovial fluid pressure thereat, thereby enhancing synovial fluid flow through passageways  426 . This reduces friction in the joint. 
     Reference is now made to  FIGS. 15A &amp; 15B , which are simplified illustrations of an aspect of the initial functionality of embodiments illustrated respectively in  FIGS. 14A &amp; 14B .  FIG. 15A  shows at A the implant  412  disposed in synovial fluid  421  between socket acetabulum socket  420  and femoral head  422 , following surgical insertion. It is seen that the shape of the implant  412  does not necessarily conform to the corresponding shapes of the articulating surfaces of the acetabulum socket  420  and the femoral head  422 . 
     Following at least some articulation of the hip joint, such as due to running or walking, as shown at B, the shape of implant  412  becomes more conformal to the corresponding shapes of acetabulum socket  420  and femoral head  422 . 
     One preferred steady-state, long term arrangement of implant  412  is shown at C, wherein the shape of the implant  412  is highly conformal to the corresponding shapes of acetabulum socket  420  and femoral head  422  and the implant floats in the synovial fluid  421  between the articulating surfaces of the acetabulum socket  420  and the femoral head  422 , as the result of equilibrium in the fluid dynamic pressures exerted on the implant  412  by the synovial fluid alongside both surfaces thereof. 
     Another preferred steady-state, long term arrangement of implant  412  is shown at D, wherein the shape of the implant  412  is somewhat less conformal to the corresponding shapes of acetabulum socket  420  and femoral head  422  and the implant partially floats in the synovial fluid  421  between the articulating surfaces of the acetabulum socket  420  and the femoral head  422 , as the result of equilibrium in the fluid dynamic pressures exerted on the implant  412  by the synovial fluid alongside both surfaces thereof and partially contacts one or both of the acetabulum socket  420  and the femoral head  422 . The operative states shown at C and D may each occur from time to time in a patient or alternatively either operative state may predominate. 
       FIG. 15B  shows at A the implant  424  disposed in synovial fluid  421  between acetabulum socket  420  and femoral head  422 , following surgical insertion. It is seen inclined passageway  427  provides synovial fluid communication between a first synovial fluid region, designated by reference numeral  430 , between implant  424  and the surgically reamed acetabulum socket  420  and a second synovial fluid region  432  between implant  424  and a corresponding femoral head  422 . 
     Following at least some articulation of the hip joint, such as due to running or walking, as shown at B, flow of synovial fluid, which may be enhanced by the action of the synovial fluid pump defined by membrane  428 , through inclined passageways  427  causes micro-rotation of the implant  424 , relative to the acetabulum socket  420 , as indicated, for example, by an arrow  434 . The micro-rotation tends to prevent the implant  424  from being frozen in position relative to either of the articulating surfaces of the joint, such as the acetabulum socket  420 . The micro-rotation also contributes to lowering friction between the implant  424  and the articulating surfaces of the joint upon joint articulation. 
     Reference is now made to  FIGS. 16A &amp; 16B , which are simplified partial illustrations of a plurality of alternative structures of a tibia/knee inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 13  and to  FIGS. 17A &amp; 17B , which are simplified illustrations of operation of the inter-surface articulating joint implant in the embodiments illustrated respectively in  FIGS. 16A  &amp;  16 B. The inter-surface articulating joint implants of the present invention are preferably formed of a resilient material such as polyurethane but alternatively may be made of a material which is liquid absorbing, such as HydroThane™ which is commercially available from Cardiotech International Ct Biomaterials. 
       FIGS. 16A &amp; 16B  represent two alternative embodiments of a tibia/knee inter-surface articulating joint implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 13 .  FIGS. 16A &amp; 16B  are pictorial illustrations of a tibia/knee inter-surface articulating joint implant  452 , of the type seen in enlargement  409 .  FIGS. 17A &amp; 17B  are sectional illustrations of the tibia/knee inter-surface articulating joint implant  452 , taken generally along lines XVIIA-XVIIA in  FIG. 16A  and lines XVIIB-XVIIB in  FIG. 16B , respectively. It is appreciated that the descriptions of  FIGS. 16A-17B  which follow are applicable to any other suitable similar type of implant. 
     Turning now to  FIGS. 16A &amp; 16B , there are seen partial illustrations of a portion of the tibia/knee inter-surface articulating joint implant  452 , constructed and operative in accordance with a preferred embodiment of the present invention.  FIG. 16A  shows the implant  452  as a generally flat element having at least one somewhat resilient protrusion  454  arranged to be tightly seated in a corresponding socket (not shown), surgically formed in the tibia  460 , preferably in snap-fit engagement therewith. Implant  452  is also preferably formed with at least one tab  462  having a somewhat resilient protrusion  464  arranged to be tightly seated in a corresponding socket  466 , surgically formed in the tibia  460 , preferably in snap-fit engagement therewith. 
     Synovial fluid  468  is interposed between implant  452  and the tibia  460  and between implant  452  and a corresponding femoral condyle  470 . In the illustrated embodiment, the implant  452  is preferably formed of a somewhat resilient material, such as polyurethane. 
       FIG. 16B  shows a portion of an alternative embodiment of a tibia/knee inter-surface articulating joint implant, here designated by reference numeral  472 , the structure of which differs from the structure of implant  472  in that tab  462  ( FIG. 16A ) is replaced by a resiliently extendible tab  473 . Resiliently extendible tab  473  includes a somewhat resilient protrusion  474  arranged to be tightly seated in socket  466 , surgically formed in the tibia  460 , preferably in snap-fit engagement therewith. 
     Reference is now made to  FIGS. 17A &amp; 17B , which are simplified illustrations of an aspect of the functionality of embodiments illustrated respectively in  FIGS. 16A &amp; 16B .  FIG. 17A  shows at A the implant  452  disposed in synovial fluid  468  between tibia  460  and femur  470 . It is seen that the shape of the implant  452  does not necessarily conform to the corresponding shapes of the articulating surfaces of the tibia  460  and the femur  470 . 
     Following at least some articulation of the knee, such as due to running or walking, as shown at B, the shape of implant  452  becomes more conformal to the corresponding shapes of the tibia  460  and the femur  470 . A preferred steady-state, long term arrangement of implant  452  is shown at C, wherein the shape of the implant  452  is highly conformal to the corresponding shapes of the tibia  460  and the femur  470  and the implant  452  floats in an anchored manner in the synovial fluid  468  between the articulating surfaces of the tibia  460  and the femur  470 , as the result of equilibrium in the fluid dynamic pressures exerted on the implant  452  by the synovial fluid alongside both surfaces thereof. The anchoring of implant  452  by protrusion  454  ( FIG. 16A ) and by tab  462  ( FIG. 16A ) maintains desired positioning of the implant  452  in the knee. 
       FIG. 17B  shows at A the implant  472  disposed in synovial fluid  468  between the tibia  460  and the femur  470 . It is seen that the shape of the implant  472  does not necessarily conform to the corresponding shapes of the articulating surfaces of the tibia  460  and the femur  470 . 
     Following at least some articulation of the knee, such as due to running or walking, as shown at B, the shape of implant  472  becomes more conformal to the corresponding shapes of the tibia  460  and the femur  470 . 
     A preferred steady-state, long term arrangement of implant  472  is shown at C, wherein the shape of the implant  472  is highly conformal to the corresponding shapes of the tibia  460  and the femur  470  and the implant  472  floats in a flexible anchored manner in the synovial fluid  468  between the articulating surfaces of the tibia  460  and the femur  470 , as the result of equilibrium in the fluid dynamic pressures exerted on the implant  452  by the synovial fluid alongside both surfaces thereof. 
     Another preferred steady-state, long term arrangement of implant  472  is shown at D, wherein the shape of the implant  472  is somewhat less conformal to the corresponding shapes of tibia  460  and femur  470  and the implant partially floats in the synovial fluid  468  between the articulating surfaces of the tibia  460  and the femur  470 , as the result of equilibrium in the fluid dynamic pressures exerted on the implant  472  by the synovial fluid alongside both surfaces thereof and partially contacts one or both of the tibia  460  and the femur  470 . The operative states shown at C and D may each occur from time to time in a patient or alternatively either operative state may predominate. 
     The flexible anchoring of implant  472  by protrusion  454  ( FIG. 16B ) and by resiliently extendible tab  473  maintains desired positioning of the implant  472  in the knee while allowing more lateral motion of the implant in the sense of  FIGS. 17A and 17B  than the arrangement shown in  FIGS. 16A and 16B . 
     Reference is now made to  FIG. 18 , which is a simplified anatomical illustration showing various applications of a meniscus implant constructed and operative in accordance with a preferred embodiment of the present invention, to  FIGS. 19A &amp; 19B , which are simplified partial illustrations of a plurality of alternative structures of a meniscus implant useful in the embodiment of  FIG. 18  and to  FIGS. 20A &amp; 20B , which are simplified illustrations of an aspect of the functionality of the meniscus implant in the embodiments illustrated respectively in  FIGS. 19A &amp; 19B . 
     There is provided in accordance with a preferred embodiment of the present invention a meniscus implant adapted to be located between articulating surfaces of a tibia and a femur, the meniscus implant being a generally thin element formed of a flexible resilient material and being adapted to be generally surrounded by synovial fluid. 
     Preferably, the meniscus implant is formed with one or more throughgoing channels for passage of synovial fluid therethrough in response to changes in fluid pressure resulting from knee joint articulation and the application of changing forces to the knee joint. 
     The meniscus implant preferably serves to decrease or eliminate frictional engagement between the articulating surfaces of the knee joint. Additionally or alternatively, articulation of the knee joint may serve to enhance desired cartilage regeneration along one or both articulating surfaces of the knee joint. 
     Turning initially to  FIG. 18 , there is provided a simplified anatomical illustration showing various applications of a meniscus implant of the type described hereinabove, constructed and operative in accordance with a preferred embodiment of the present invention. A left medial meniscus implant  500 , constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  502  for a straight leg orientation. A left lateral meniscus implant  504 , constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  506  for a straight leg orientation. A right medial meniscus implant  508 , constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  510  for a bent knee orientation. A right lateral meniscus implant  512 , constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  514  for a bent knee orientation. 
     Reference is now made to  FIGS. 19A &amp; 19B , which are simplified partial illustrations of a plurality of alternative structures of a medial meniscus implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 18  and to  FIGS. 20A &amp; 20B , which are simplified illustrations of operation of the medial meniscus implant in the embodiments illustrated respectively in  FIGS. 19A &amp; 19B . The meniscus implants of the present invention are preferably formed of a resilient material such as polyurethane but alternatively made be made of a material which is liquid absorbing, such as HydroThane™ which is commercially available from Cardiotech International Ct Biomaterials. 
       FIGS. 19A &amp; 19B  represent two alternative embodiments of a meniscus implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 18 .  FIGS. 19A and 19B  are pictorial illustrations of two alternative embodiments of medial meniscus implant  500 .  FIGS. 20A and 20B  each include sectional illustrations of meniscus implants  500  and  508 , respectively taken generally along lines XXA-XXA in  FIG. 19A  and lines XXB-XXB in  FIG. 19B . 
     Turning now to  FIGS. 19A &amp; 19B , there are seen partial illustrations of a portion of meniscus implant  552  of the type of meniscus implant  500 , constructed and operative in accordance with a preferred embodiment of the present invention.  FIG. 19A  shows the implant  552  as a generally kidney-shaped, partially hollow generally flat element having at least one somewhat resilient protrusion  554  arranged to be tightly seated in a corresponding socket (not shown), surgically formed in the tibia, preferably in snap-fit engagement therewith. Implant  500  is also preferably formed with at least one tab  562  having a somewhat resilient protrusion  564  arranged to be tightly seated in a corresponding socket (not shown), surgically formed in the tibia, preferably in snap-fit engagement therewith. 
     As noted above, implant  500  is preferably partially hollow and preferably includes a hollow portion  566  which tapers down to a relatively thin non-hollow portion  568  along a transition line  570 . Preferably at least one valve  571  is formed in hollow portion  566  to permit filling of the hollow portion  566  with a suitable fluid or gel, such as HydroSlip C which is commercially available from Cardiotech International Ct Biomaterials, Salubria which is commercially available from Salumedica, Llc of 112 Krog Street, Suite 4 Atlanta, Ga. or PuraMatrix which is commercially available from 3DM Inc. of Cambridge, Mass. As a further alternative, the hollow portion  566  may be filled with a self-polymerizing material such as in situ curable polyurethane which is commercially available from Advanced Bio Surfaces, Inc. of 5909 Baker Road, Suite 550, Minnetonka, Minn. 
     Alternatively at least one valve  571  may be obviated and the hollow portion  566  may be sealed and contain any suitable fluid. It is appreciated that the hollow portion  566  may be filled and sealed at the factory or at the time of implantation, such as in situ. 
     Synovial fluid is interposed between implant  552  and the tibia and between implant  552  and a corresponding femoral condyle. 
       FIG. 19B  shows a portion of an alternative embodiment of a meniscus implant, here designated by reference numeral  572 , the structure of which differs from the structure of implant  552 , shown in  FIG. 19A , in that apertures  574  are formed in the walls defining a hollow portion  576  to enable synovial fluid to readily communicate therethrough and to be pumped by changes in the volume of the interior of the hollow portion  576  resulting from articulation of the knee joint. Another feature shown in  FIG. 19B , which feature may also be incorporated in the embodiment of  FIG. 19A , is that tab  562  ( FIG. 19A ) is replaced by a resiliently extendible tab  583 . Resiliently extendible tab  583  includes a somewhat resilient protrusion  584  arranged to be tightly seated in a corresponding socket (not shown), surgically formed in the tibia, preferably in snap-fit engagement therewith. 
     Reference is now made to  FIGS. 20A &amp; 20B , which are simplified illustrations of an aspect of the functionality of embodiments illustrated respectively in  FIGS. 19A &amp; 19B .  FIG. 20A  shows at A the implant  552  disposed between a tibia  590  and a femur  592 . Synovial fluid  598  is interposed between implant  552  and the tibia  590  and between implant  552  and a corresponding femoral condyle. It is seen that at stage A, when the leg is relatively straight, as shown in enlargement  502  of  FIG. 18 , a relatively large percentage of the surface area of the implant is engaged by the tibia and the femur. 
     It is seen that at stage B, when the knee is bent, as shown in enlargement  510  of  FIG. 18 , a relatively small percentage of the surface area of the implant is engaged by the tibia  590  and the femur  592 . It is appreciated that the implant shown at B is the right medial meniscus implant  508  ( FIG. 18 ), while the implant shown at A is the left medial meniscus implant  500  ( FIG. 18 ). It is appreciated that there exist an extremely large number of operative orientations of the meniscus implant which are not shown here for the sake of conciseness. 
       FIG. 20B  shows at A the implant  572  ( FIG. 19B ) disposed between a tibia  594  and a femur  596 . It is seen that at stage A, when the leg is relatively straight, as shown in enlargement  502  of  FIG. 18 , a relatively large percentage of the surface area of the implant is engaged by the tibia  594  and the femur  596 . 
     It is appreciated that the implant shown at B is the right medial meniscus implant  508  ( FIG. 18 ), while the implant shown at A is the left medial meniscus implant. It is appreciated that there exist an extremely large number of operative orientations of the meniscus implant which are not shown here for the sake of conciseness. 
     It is seen that at stage B, when the knee is bent, as shown in enlargement  510  of  FIG. 18 , a relatively small percentage of the surface area of the implant is engaged by the tibia  594  and the femur  596 . It is noted that due to the pumping action produced by articulation of the knee joint on the apertured meniscus implant  572 , a relatively large amount of synovial fluid  598  is provided in the vicinity of the meniscus implant  572  and between the meniscus implant and the corresponding articulating surfaces of the tibia  594  and the femur  596 . 
     Preferably, the synovial fluid  598  is present along the walls of both the hollow and non-hollow portions of the meniscus implant  572 . 
     It is a particular feature of the present invention that the structure of apertured, synovial fluid pumping implant  572  substantial reduces friction, increases lubrication and enhances the overall ease of knee joint articulation. 
     Reference is now made to  FIGS. 21A ,  21 B,  21 C and  21 D, which are sectional illustrations of a plurality of alternative constructions of the meniscus implant of  FIGS. 18-20B .  FIG. 21A  shows a unitary, integrally formed meniscus implant of the type shown in  FIG. 18 . This implant can be manufactured by injection molding.  FIG. 21B  shows an alternative embodiment of a meniscus implant of the type shown in  FIG. 18  which comprises folded-over sheet material which is typically joined by press-fit joints or any other suitable bonding technique.  FIG. 21C  shows a further alternative embodiment of a meniscus implant of the type shown in  FIG. 18  which comprises a pair of generally web-type elements which are joined along two seams by press-fit joints or any other suitable bonding technique. 
       FIG. 21D  shows an embodiment of a meniscus implant of the type shown in  FIG. 18  which comprises mutually engaging shape stabilizing internal structural elements  599  which cooperate with a polymerizeable material  600  in the interior of a hollow portion  601  to help maintain a desired three-dimensional shape of implant notwithstanding articulation of the knee joint. This structure is particularly useful for in-situ filling of the interior of the hollow portion  601 . 
     Reference is now made to  FIG. 22 , which is a simplified anatomical illustration showing various applications of a ball implant constructed and operative in accordance with a preferred embodiment of the present invention, to  FIGS. 23A ,  23 B &amp;  23 C, which are simplified partial illustrations of a plurality of alternative structures of a ball implant useful in the embodiment of  FIG. 22  and to  FIGS. 24A &amp; 24B , which are simplified illustrations of aspects of the functionality of the ball implants in the embodiments illustrated respectively in  FIGS. 23A &amp; 23B . 
     There is provided in accordance with a preferred embodiment of the present invention a ball implant adapted for articulation with an articulating socket of a joint, the ball implant being a shock-absorbing multi-layer assembly. 
     In accordance with one embodiment of the invention, the ball implant is formed with one or more throughgoing channels for passage of synovial fluid therethrough in response to changes in fluid pressure resulting from joint articulation and the application of changing forces to the joint. 
     In accordance with another embodiment of the present invention, a personalized fit, in situ configurable, ball implant is provided. Additionally or alternatively, articulation of the joint may serve to enhance desired cartilage regeneration along an articulating surface of a ball socket. 
     Turning initially to  FIG. 22 , there is provided a simplified anatomical illustration showing various applications of a ball implant of the type described hereinabove, constructed and operative in accordance with a preferred embodiment of the present invention. A hip joint ball implant  602 , constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  603 . A shoulder joint ball implant  604 , constructed and operative in accordance with a preferred embodiment of the present invention, is shown in an enlargement designated by reference numeral  606 . 
     Reference is now made to  FIGS. 23A ,  23 B &amp;  23 C, which are simplified partial illustrations of a plurality of alternative structures of a ball implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 22  and to  FIGS. 24A &amp; 24B , which are simplified illustrations of operation of the ball implant in the embodiments illustrated respectively in  FIGS. 23A &amp; 23B . 
       FIGS. 23A ,  23 B &amp;  23 C, present three alternative embodiments of a ball implant, constructed and operative in accordance with a preferred embodiment of the present invention, useful in the embodiment of  FIG. 22 .  FIGS. 23A ,  23 B and  23 C are pictorial illustrations of three alternative embodiments of ball implant  602 .  FIGS. 24A and 20B  each include sectional illustrations of ball implants  602  and  604 , respectively taken generally along respective lines XXIVA-XXIVA and XXIVB-XXIVB in enlargements  603  and  606 . 
     Turning now to  FIGS. 23A ,  23 B &amp;  23 C, there are seen partially cut-way illustrations of three alternative embodiments of a portion of ball implant  602 , constructed and operative in accordance with a preferred embodiment of the present invention. 
       FIG. 23A  shows the implant  602  as a generally ball-shaped, partially hollow multi-layer assembly arranged to be tightly seated onto a top portion of a conventional replacement femoral stem  610 . The implant preferably comprises a replacement femoral stem socket  612 , preferably formed of polyurethane having a Shore hardness designated as  70 D and having an outer facing rim  614 . Preferably mounted onto a circumferential recess  616  formed on an outer surface of socket  612  is a generally ball shaped hollow outer element  618 , preferably formed of polyurethane having a Shore hardness designated as  80 A and defining an articulating surface  620 . Disposed within element  618  is a core element  622 , preferably formed of foamed polyurethane of the same type used in element  618 . Located between elements  618  and  622  is at least one relatively thin reinforcing layer  624 , typically formed of KEVLAR® or carbon cloth. Core element  622  may be advantageously formed with at least one synovial fluid void  626 . 
     At least one synovial fluid communication passageway  630  communicates with at least one void  626  at locations adjacent rim  614 . A plurality of synovial fluid communication passageways  632  communicate between at least one void  626  through core element  622 , at least one reinforcing layer  624  and element  618  with the articulating surface  620 , thus providing synovial fluid communication with the articulating surface  620  of the implant. Preferably one-way flow valves (not shown) are associated with most or all of passageways  630  and  632 . Pumping action produced by articulation of the ball implant  602  relative to an acetabulum socket (not shown) causes a relatively large amount of synovial fluid to be provided in the articulation region between the articulating surface  620  of the ball implant  602  and the corresponding articulating surface of the acetabulum socket (not shown). The pumping action preferably is constrained by the valves (not shown) such that synovial fluid flows towards the void  626  only via passageways  630  and from the void to the articulation region only via passageways  632 . 
       FIG. 23B  shows another embodiment of the implant  604  as a generally ball-shaped, partially hollow multi-layer assembly arranged to be tightly seated onto a top portion of a conventional replacement femoral stem  640 . The implant preferably comprises a replacement femoral stem socket  642 , preferably formed of polyurethane having a Shore hardness designated as  70 D and having an outer facing rim  644 . Preferably mounted onto a circumferential recess  646  formed on an outer surface of socket  642  is a generally ball shaped hollow outer element  648 , preferably formed of polyurethane having a Shore hardness designated as  80 A and defining an articulating surface  650 . Disposed within element  648  is a core element  652 , preferably formed of foamed polyurethane of the same type used in element  648 . Located between elements  648  and  652  is at least one relatively thin reinforcing layer  654 , typically formed of KEVLAR® or carbon cloth. Core element  652  may be advantageously formed with at least one fluid-filled void  656 . 
     At least one selectably inflatable, selectably expandable void  658  is preferably provided between element  648  and reinforcing layer  654  over generally the entire areas thereof. At least one inflation passageway  660  having an associated one-way valve  662 , communicates between a location adjacent rim  644  and the interior of void  658  to enable a spherical radius determining material to be selectably inserted into void  658  in order to enable adaptation of the overall radius of the generally spherical articulating surface  650  in situ so as to provide personalized fit of the ball implant to a patient&#39;s acetabulum socket. 
       FIG. 23C  shows a further alternative embodiment of the implant  668  as a generally ball-shaped, partially hollow multi-layer assembly arranged to be tightly seated onto a top portion of a conventional replacement femoral stem  670 . The implant preferably comprises a replacement femoral stem socket  672 , preferably formed of polyurethane having a Shore hardness designated as  70 D and having an outer facing rim  674 . Preferably mounted onto a circumferential recess  676  formed on an outer surface of socket  672  is a generally ball shaped hollow outer element  678 , preferably formed of polyurethane having a Shore hardness designated as  80 A and defining an articulating surface  680 . Disposed within element  678  is a core element  682 , preferably formed of foamed polyurethane of the same type used in element  678 . Located between elements  678  and  682  is at least one relatively thin reinforcing layer  684 , typically formed of KEVLAR® or carbon cloth. Core element  622  may be advantageously formed with fluid-filled voids, which may be, for example, in a generally spherical shape, as shown at reference numeral  686  or a generally annular shape, as shown at reference numeral  688 . The voids provide desired flexibility of core element  682 . 
     Reference is now made to  FIGS. 24A &amp; 24B , which are simplified illustrations of aspects of the functionality of the embodiments illustrated respectively in  FIGS. 23A &amp; 23B .  FIG. 24A  shows at A the implant  602  in the embodiment of  FIG. 23A , disposed in articulating engagement with an acetabulum socket  690  and a force, indicated by an arrow  692  being exerted on the ball implant  602  via the socket  690 . Such a situation occurs cyclically when a person is walking or running. The force, indicated by arrow  692  produces deformation of the ball implant  602  and consequent temporary reshaping of the articulating surface  620 , from its non-deformed geometry as shown at reference numeral  694  to a deformed geometry as shown at reference numeral  696 . 
     The deformation of ball implant  602  produces compression of core element  622 , reinforcing layer  624  and hollow outer element  618 , which are shown as a single layer  622 , which compression effectively reduces the volume of void  626  and thus causes flow of synovial fluid from void  626  via passageways  632  and one-way valves (not shown) into the articulation region  697 , as shown by arrows  698 . 
     At stage B there is seen the implant  602  in the embodiment of  FIG. 23A , disposed in articulating engagement with an acetabulum socket  690  in the absence of the force, indicated by an arrow  692  at stage A being exerted on the ball implant  602  via the socket  690 . Such a situation occurs cyclically when a person is walking or running, interspersed with the situation shown at stage A. The absence of the force, indicated by arrow  692 , eliminates deformation of the ball implant  602  and allows articulating surface  620  to return to its non-deformed geometry as shown at reference numeral  694  from the deformed geometry as shown at reference numeral  696 . 
     The elimination of the deformation of ball implant  602  eliminates compression of core element  622 , reinforcing layer  624  and hollow outer element  618 , which are shown as a single layer  622 , which effectively returns the volume of void  626  to its volume prior to stage A, resulting in the application of suction and thus causes flow of synovial fluid to void  626  via passageways  630  and one-way valves (not shown), as shown by arrows  699 . 
       FIG. 24B  shows at A the implant  604  in the embodiment of  FIG. 23B , initially placed in articulating engagement with a natural acetabulum socket  710 . Preferably a relatively thin spacer element  712  is interposed between the implant  604  and the acetabulum socket  710 . It is seen that the outer radius of the articulating surface  650  of implant  604  is less than a desired radius for articulation with a corresponding articulating surface  714  of acetabulum socket  710 . 
     At stage B, insertion of a fluid, preferably but not necessarily a settable polyurethane material, for example in situ curable polyurethane which is commercially available from Advanced Bio Surfaces, Inc. of 5909 Baker Road, Suite 550, Minnetonka, Minn., via at least one passageway  660  and corresponding one-way valve  662  into void  658 , thereby at least partially filling the void and producing expansion of element  648  preferably in a spherically uniform manner, thereby increasing the radius of the articulating surface  650 . 
     At stage C, insertion of a fluid, preferably but not necessarily a settable polyurethane material, for example in situ curable polyurethane which is commercially available from Advanced Bio Surfaces, Inc. of 5909 Baker Road, Suite 550, Minnetonka, Minn., via at least one passageway  660  and corresponding one-way valve  662  into void  658 , thereby bring the radius of the articulating surface  650  to a desired radius, which is smaller than the radius of the articulating surface  714  of the acetabulum socket  710  by an amount represented by the thickness of the spacer element  712 . 
     At stage D, the spacer element  712  is removed, thus allowing a desired clearance  718  between the respective articulating surfaces  650  and  714  of the ball implant  604  and the acetabulum socket  710 , to be filled by synovial fluid  720 . 
     It is appreciated that in this manner, regeneration of cartilage along the articulating surface  714  of the ball implant  604  may be enhanced by the precise matching of radii of surfaces  650  and  714 . 
     It is appreciated that the ball implant devices shown in  FIGS. 22-24B  may be configured and constructed as unitary devices, including a stem, rather than being mounted on a stem via a sleeve. 
     Reference is now made to  FIG. 25 , which is a simplified pictorial illustration of a groove reamer constructed and operative in accordance with a preferred embodiment of the present invention, useful, for example in the embodiment of  FIG. 13 , to  FIG. 26 , which is a simplified composite illustration showing the structure of the groove reamer of  FIG. 25  and to  FIGS. 27A ,  27 B,  27 C and  27 D, which are simplified sectional illustrations illustrating various stages of the operation of the groove reamer of  FIGS. 25 and 26 . 
     As seen in  FIGS. 25 and 26 , there is provided a groove reamer  800  comprising a central bone anchor element  802  which is preferably integrally formed of a generally spherical spiked bone engagement surface  804  and a central shaft  806  extending along an axis  808 , having a threaded portion  810  adjacent the bottom thereof. The central bone anchor element  802  is preferably formed of metal, such as titanium or aluminum. 
     Mounted for rotation about central shaft  806  is a rotational driving assembly  812  including a first handle  814 , preferably integrally formed with an elongate hollow shaft  816 , which is sized to rotationally accommodate central shaft  806 . Hollow shaft  816  terminates in a rotational driving plate  818 . Coupled for rotation together with rotational driving plate  818  is a conical rotational and axial driving element  820  having a central threaded bore  822 , which threadably engages threaded portion  810  of central shaft  806 . Preferably rotational driving plate  818  is formed with a plurality of axially extending pins  824  which extend into corresponding axially extending sockets  826  formed in conical rotational and axial driving element  820 . 
     In accordance with a preferred embodiment of the present invention, rotational driving plate  818  is formed with a plurality of slidable knife support channels  830  and conical rotational and axial driving element  820  is formed with a plurality of correspondingly positioned slidable knife support channels  832 , which extend generally at an angle with respect to channels  830 . 
     A plurality of knives  840  are each slidably seated in a pair of corresponding channels  830  and  832  and are mounted on a resilient knife support ring  842  which permits simultaneous radially outward and rotational displacement of the knives  840  in response to simultaneous axial and rotational movement of conical rotational and axial driving element  820  in threaded engagement with threaded portion  810  of central shaft  806  in response to rotation of first handle  814  in a direction indicated by an arrow  844 . 
     A radially displaceable bone engagement assembly  850 , typically comprises a plurality of integrally formed flexible engagement elements  852 , each comprising a hand engageable portion  854 , lying intermediate first and second retaining portions  856  and  858  and a radial bone engaging tooth portion  860 . Assembly  850  preferably comprises six integrally formed flexible engagement elements  852  which are held together about hollow shaft  816  at respective first and second retaining portions  856  and  858  by a corresponding pair of retaining bands  862  and  864  to collectively define a second handle  866  at hand engageable portions  854  thereof. 
     As will be described hereinbelow in greater detail, an operator, such as a surgeon, grasping second handle  866  with one hand causes bending of flexible engagement elements  852  about retaining portions  856 , causing bone engaging tooth portions  860  to be displaced radially outwardly into retaining engagement with the walls of a bone socket being reamed. 
     Referring now to  FIGS. 27A-27D , it is seen that initially, as seen in  FIG. 27A , the surgeon places the reamer  800  with central bone anchor element  802  in a bone socket  868  to be reamed and pushes first handle  814  axially downwardly as indicated by an arrow  870 , causing the spikes on generally spherical spiked bone engagement surface  804  to engage the bone surface at socket  868 . This anchors the central bone anchor element  802  against rotation with respect to socket  868 . 
       FIG. 27B  shows engagement of the radial bone engagement tooth portions  860  with side surfaces of the socket  868 . This engagement is produced by the surgeon squeezing his hand which engages the second handle  866  and thus forcing the hand engageable portions  854  of integrally formed flexible engagement elements  852  radially inwardly, as indicated by arrows  874 , producing corresponding radially outward displacement of tooth portions  860  into retaining engagement with the side surfaces of socket  868 . This further stabilizes the reamer with respect to the bone socket  868 . 
       FIG. 27C  illustrates the beginning of reaming operation, which is produced by rotation of first handle  814  about axis  808  such as in a direction indicated by arrows  844 . The rotation of first handle  814  causes rotation of conical rotational and axial driving element  820  about axis  808  and consequent corresponding axially forward displacement of conical rotational and axial driving element  820  due to the threaded engagement of threaded portion  810  of central shaft  806  with threaded bore  822 . This forward movement of conical rotational and axial driving element  820  drives knives  840 , which are slidably seated in channels  830  and  832  ( FIG. 26 ) in a radially outward direction, indicated by arrows  880 , into cutting engagement with the bone socket, thus beginning to produce a circumferential channel  882  therein. As seen in  FIG. 27C , a recess  884  is preferably formed in the central bone anchor element  802 . 
       FIG. 27D  illustrates the completion of the reaming operation produced by rotation of first handle  814  about axis  808  such as in a direction indicated by arrows  844 . Continued rotation of first handle  814  causes rotation of conical rotational and axial driving element  820  about axis  808  and consequent corresponding axially forward displacement of conical rotational and axial driving element  820  due to the threaded engagement of threaded portion  810  of central shaft  806  with threaded bore  822 . This forward movement of conical rotational and axial driving element  820  drives knives  840 , slidably seated in channels  830  and  832  ( FIG. 26 ) further in a radially outward direction, indicated by arrows  880 , into cutting engagement with the bone socket, thus beginning to produce a circumferential channel  882  therein. The rotational and axial displacement of the conical rotational and axial driving element  820  typically stops when the conical rotational and axial driving element  820  engages the bottom of a corresponding recess  884  formed in the central bone anchor element  802  above the generally spherical spiked bone engagement surface  804 . 
     It is a particular feature of the present invention that the knives  840  are slidably supported for radial displacement and cutting by the mechanism described hereinabove. 
     Removal of the reamer  800  may readily be accomplished by rotating the first handle in an opposite direction. The resiliency of ring  842  is operative to radially retract the knives  840 . 
     It is appreciated that the extension and retraction of knives  840 , may be gauged by a gauging apparatus, and the gauging may be displayed to an operator for monitoring the displacement of knives  840 . 
     It is also appreciated that the rotation of elongate hollow shaft  816  and rotational driving plate  818  may be empowered by an electronic or hydraulic system, and the operator may utilize the display of extension and retraction of the knives to determine the completion of groove  882  to a precise desired depth. The electronic or hydraulic system may replace handle  814 . 
     Reference is now  FIG. 28 , which is a simplified composite partially sectional exploded-view illustration of a socket implant assembly and implanter useful therewith, constructed and operative in accordance with a preferred embodiment of the present invention and to  FIG. 29 , which is a simplified composite sectional assembled-view illustration of the socket implant assembly and implanter of  FIG. 28 , taken in the section plane of  FIG. 28 . References to top, bottom, upper and lower are in the context of  FIGS. 28 and 29 . 
     As seen in  FIGS. 28 and 29 , there is provided an implanter  900  comprising a central shaft  902  extending along an axis  904  and having an outer facing threaded portion  906  adjacent the top thereof. Mounted onto central shaft  902  for driving rotation thereof is a rotational driving assembly  908  including handle  910 , preferably fixed to central shaft  902  by a transversely extending pin  912 . The bottom of central shaft  902  is formed with an end portion  914  having a reduced radius and defining a shoulder  916  with respect to the remainder of the central shaft lying thereabove. Preferably, the bottom surface  918  of the end portion  914  is formed with a bevel  920 . 
     A sleeve  922  is disposed about central shaft  902  and includes an inner facing threaded portion  924  at the top thereof. Sleeve  922  has a generally uniform inner surface  926  extending therealong below threaded portion  924 . The outer surface of sleeve  922  includes a circumferential recess  928  adjacent the top thereof, defining a retaining circumferential protrusion  930  which may be engaged by a protective sleeve  932 , depending from handle  910 , which preferably is provided in order to prevent inadvertent engagement of a user&#39;s hand or finger between the top of sleeve  922  and handle  910 . 
     A central portion  934  of the outer surface of sleeve  922  is preferably knurled in order to provide a gripping surface for user engagement during implanting. Below central portion  934 , there is preferably formed a peripheral protrusion  936  of uniform radius. Below peripheral protrusion  936  and spaced therefrom along axis  904  is a beveled protrusion  938 , which tapers inwardly and downwardly to a bottom edge  940  of the sleeve  922 . The space between peripheral protrusion  936  and beveled protrusion  938  defines a recess  942 . 
     Arranged for operational engagement with central shaft  902  and sleeve  922  is a disposable implant mounting assembly  950  including a flexible central element  952 , a pair of outer elements  954  and a bottom element  956 . 
     Flexible central element  952  preferably is formed of a relatively rigid plastic material, such as polyethylene and is a generally rotationally symmetric. Element  952  is formed with a generally flat top surface  958  which surrounds a generally axial collar  960  and is joined thereto by a beveled edge  962 . Extending outwardly and downwardly from top surface  958  is an upper peripheral outer surface  964 . Extending downwardly from upper peripheral outer surface  964  is an intermediate peripheral outer surface  966  which terminates in a peripheral recess  968 . Below peripheral recess is a lower peripheral surface  970  which terminates in a lower edge  972 . 
     Interiorly of intermediate peripheral outer surface  966 , peripheral recess  968  and lower peripheral surface  970  there is provided an interior facing recess  974  which defines an upper interior facing shoulder  976 . 
     A plurality, preferably two, radially outward extending tabs  978  are formed, preferably in oppositely facing locations at the junction of upper peripheral outer surface  964  and intermediate peripheral outer surface  966 . 
     A plurality of slits  980 , preferably six in number, are preferably formed in flexible central element  952 , to provide flexibility thereof, and extend radially in evenly spaced azimuthal distribution through flat top surface  958  and upper peripheral outer surface  964 . 
     Bottom element  956  preferably is formed with a central collar portion  982  which is integrally joined at its bottom to a curved generally radially extending portion  984  having a peripheral edge  986  which is configured to be seated in recess  974  of flexible central portion  952  against shoulder  976 . Preferably a plurality of radially extending ribs  988  are provided at the top of radially extending portion  984 . A ring  992  integrally depends from radially extending portion  984  slightly inwardly of peripheral edge  986 . Ring  992  defines a peripheral outwardly facing surface  994  and an adjacent downwardly facing surface  995 . 
     Outer elements  954  together define a generally hemispherical body and preferably each include a thickened generally flat top facing surface  996 , which defines a collar  998 , an upper peripheral surface  1000 , an intermediate peripheral surface  1002  and a lower peripheral surface  1004 . Apertures  1006  are preferably formed in intermediate peripheral surface  1002  to accommodate tabs  978  of flexible central element  952  for desired mounting of outer elements  954  with respect thereto. Apertures  1006  each preferably include a relatively widened portion  1008  for receiving a tab  978  and a relatively narrowed portion  1010  adjacent widened portion  1008  for retaining tab  978 . 
     An inner, relatively rigid implant element  1020 , preferably formed of metal or ceramic, preferably includes a generally circular peripheral rim  1022  below which is defined a generally circular, peripheral, outer-facing recess  1024 . The surface portion  1025  of the outer surface of element  1020  is generally spherical. The interior surface  1026  of element  1020  defines a generally spherical articulating surface. Rim  1022  is preferably formed with a beveled edge  1028 . 
     An outer, relatively resilient implant element  1030 , preferably formed of polyurethane, preferably includes a generally circular inwardly facing peripheral rim  1032 , which is adapted to be seated in recess  968  of flexible central element  952 . Below rim  1032  is an inwardly tapered portion  1034  which terminates in an inwardly facing peripheral protrusion  1036  having a downwardly facing beveled edge  1038  adapted to engage beveled edge  1028  of inner implant element  1020 . 
     Below beveled edge  1038  is an inwardly facing recess  1040  which is adapted to engage rim  1022  of inner implant element  1020 . Disposed below inwardly facing recess  1040  is a inwardly facing protrusion  1042  which is adapted to engage recess  1024  of inner implant element  1020 . The portion  1043  of the inner facing surface of outer implant element  1030  lying below protrusion  1042  is generally spherical and adapted to engage surface portion  1025  of inner implant element  1020 . 
     The outer surface  1044  of implant element  1030  is generally spherical and preferably includes a peripheral protrusion  1046  which lies intermediate therealong. 
     In accordance with a preferred embodiment of the present invention, reinforcing material  1048  may be provided at one or more locations between surface portions  1043  and  1044 . Preferably such reinforcement is provided generally at a location which lies against a naturally occurring acetabulum notch in a patient&#39;s acetabulum. 
     Reference is now made to  FIGS. 30A ,  30 B,  30 C,  30 D,  30 E and  30 F, which are simplified illustrations of assembly of the socket implant assembly of  FIGS. 28 and 29 .  FIG. 30A , shows the flexible central element  952  mounted upside-down on an assembly fixture  1050  having an elongate portion  1052  including at least two elongate protrusions  1053  which are adapted to be seated in at least one pair of opposite slits  980 , thereby preventing relative rotation between the flexible central element  952  and the assembly fixture  1050 . 
       FIG. 30B  shows bottom element  956  seated in recess  974  against shoulder  976 .  FIG. 30C  shows inner implant element  1020  seated at the junction of surfaces  994  and  995  of bottom element  956 . 
       FIG. 30D  shows outer implant element  1030  seated with rim  1032  in recess  968  of flexible central element  952 .  FIG. 30E  shows outer elements  954  being displaced axially inwardly with respect to flexible central element  952  such that tabs  978  engage relatively wide portions  1008  of apertures  1006 . 
       FIG. 30F  shows outer elements  954  being rotated in a direction indicated by an arrow  1060  relative to mounting appliance  1050  and to flexible central element  952 , such that tabs  978  engage relatively narrow portions  1010  of apertures  1006 , thus retaining outer elements  954  in desired positions relative to flexible central element  952 . Thereafter, the assembled socket implant assembly  1070 , including the disposable implant mounting assembly  950  together with implant elements  1020  and  1030 , may be detached from mounting appliance  1050 . 
     Reference is now made to  FIGS. 31A ,  31 B and  31 C are simplified illustrations of mounting of a socket implant assembly  1070  onto an implanter tool, a function which is preferably performed at a hospital by a nurse or technician. 
       FIG. 31A  shows the assembled socket implant assembly  1070  ready for mounting onto the implanter  900 .  FIG. 31B  shows a first stage of relative axial displacement of the assembled socket implant assembly  1070  and the implanter  900  along axis  904 . It is seen that beveled edge  938  of sleeve  922  of the implanter  900  engages beveled edge  962  of flexible central element  952  and forces collar  960  outwardly, preliminary to snap-fit engagement therewith.  FIG. 31C  shows snap-fit engagement of collar  960  in recess  942  of sleeve  922 . It is noted that the beveled edge  920  of central shaft  902  is located at the top of central collar portion  982  of bottom element  956 . The apparatus of  FIGS. 28 and 29  is now ready for insertion of the implant elements  1020  and  1030  into the acetabulum of a patient. 
     Reference is now made to  FIGS. 32A ,  32 B,  32 C and  32 D, which are simplified illustrations of implanting a socket implant employing the apparatus of FIGS.  28  and  29 . Prior to initial insertion of the assembled socket implant assembly  1070 , the patient&#39;s acetabulum is preferably spherically reamed in a conventional manner and is then reamed to define circumferential groove  882  ( FIG. 27D ), preferably in a manner described hereinabove with reference to  FIGS. 25-27D . 
       FIG. 32A  shows snap fit engagement of protrusion  1046  of outer implant element  1030  with circumferential groove  882 . This snap fit engagement is produced by axial motion of the implanter  900  along axis  904  in a direction indicated by an arrow  1080 . 
       FIG. 32B  shows rotation of the handle  910  about axis  904  in a direction indicated by an arrow  1082 , while sleeve  922  is held static. The rotation of handle  910  produces downward axial displacement of central shaft  902 , in a direction indicated by an arrow  1084  relative to sleeve  922  due to the threaded engagement therebetween and thus relative to the flexible central element  952 . This axial displacement causes downward displacement of bottom element  956  and inner implant element  1020  relative to flexible central element  952  in the direction indicated by arrow  1084  due to engagement of shoulder  916  of central shaft  902  with central collar portion  982  of bottom element  956 . Engagement of outer surface  1025  of inner implant element  1020  with protrusion  1042  of outer implant element  1030  produces slight deformation of protrusion  1042 , preliminary to snap-fit engagement between inner implant element  1020  and outer implant element  1030  due to engagement between protrusion  1042  and recess  1024  formed on the outer surface of the inner implant element  1020 . 
       FIG. 32C  shows the full snap fit engagement.  FIG. 32D  shows the inner and outer implant elements  1020  and  1030  in place in the acetabulum of the patient, decoupled from the implanter  900  and the disposable implant mounting assembly  950 . It is seen that portions  1032  and  1034  of the outer implant element are preferably removed. Alternatively, portions  1032  and  1034  may be obviated in an arrangement where protrusion  1036  engages a corresponding recess on the central flexible element  952  ( FIG. 28 ). It is a particular feature of an embodiment of the present invention that protrusion  1036  of the outer implant element covers and thus protects edge  1028  of rim  1022  of inner implant element. 
     It is appreciated that an outer implantable element, such as outer implantable element  1030 , may be formed with a plurality of discrete protrusions, adapted to engage corresponding discrete recesses in the acetabulum of the patient. In such an embodiment, an inner implantable element, such as inner implantable element  1020 , may be formed with a plurality of discrete protrusions adapted to engage the outer implantable element. 
     Reference is now made to  FIG. 33 , which is a simplified composite exploded-view illustration of a socket implant assembly and implanter useful therewith, constructed and operative in accordance with another preferred embodiment of the present invention. The embodiment of  FIG. 33  is identical to that of  FIGS. 28 and 29  with a variation in the inner implant element, here designated by reference numeral  1120  and the outer implant element, here designated by reference numeral  1130 . 
     In this embodiment an outer surface  1135  of the inner implant element  1120  is smooth other than for a circumferential protrusion  1136 , intermediate therealong. The outer implant element  1130  is formed without protrusions  1042  and  1046  which were present in the embodiment of  FIGS. 28-32D . 
       FIG. 34  shows full insertion of inner and outer implant elements  1120  and  1130 . It is seen that protrusion  1136  forces a correspondingly located portion of outer implant element  1130  into locking engagement with a corresponding reamed recess  1140  formed in the patient&#39;s acetabulum. 
     It is appreciated that the gripping mechanism of implanter  900  and disposable implant mounting assembly  950  may alternatively be constructed as an integral mechanism, such as a gripping claws mechanism, of an implanter such as implanter  900 . 
     It is appreciated that an outer implantable element, such as outer implantable element  1130 , may be adapted to engage discrete recesses in the acetabulum of the patient. In such an embodiment, an inner implantable element, such as inner implantable element  1120 , may be formed with a plurality of discrete protrusions adapted to engage the outer implantable element. 
     It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the invention includes both combinations and sub-combinations of various features described herein as well as variations which would occur to persons reading the foregoing description and which are not in the prior art.