Abstract:
Methods and devices for sculpting bones, particularly in preparation for implanting prosthetic devices to replace articulating bone joint surfaces. Improved bone removal devices including burr mills driven by gears and loop drives are provided. Reciprocating cutters and belt cutters are also provided. Some devices have either integral or removable expandable portions to vary the force and bone resection depth. Devices can have irrigation ports and plenums to remove bone fragments. Some cutters are dual cutters, adapted to remove bone in two or more regions, such as the knee joint, simultaneously.

Description:
TECHNICAL FIELD 
     This invention relates to implants and instruments for use in cutting and preparing bone, for example, in total and partial knee arthroplasty. Such instruments are applicable in other total and partial joint replacement surgeries which include, but are not limited to the hip, the shoulder, the ankle, the elbow, the joints of the hand, the joints of the wrist, the joints of the foot and the temporal mandibular joint, articulating joints such as the knee and hip, and also motion segments of the spine. 
     BACKGROUND OF THE INVENTION 
     A joint, such as the ankle, knee, hip or shoulder, generally consists of two or more relatively rigid bony structures that maintain a relationship with each other. In the case of the spine, a motion segment generally consists of two vertebral bodies, a disc and two facet joints. Soft tissue structures spanning the bony structures hold the bony structures together and aid in defining the motion of one bony structure relative to the other. In the knee, for example, the bony structures are the femur, tibia and patella. Soft tissue structures spanning the knee joint, such as muscles, ligaments, tendons, menisci, and capsule, provide force, support and stability to facilitate motion of the knee. Muscle and tendon structures spanning the knee joint, as in other joints of the body and in the spine provide dynamics to move the joint in a controlled manner while stabilizing the joint to function in an orderly fashion. The joint is dynamically stabilized by contraction of primary muscles to move the joint in a desired direction combined with antagonistic muscle contraction to direct resultant joint loads within favorable orientation limits relative to the bony structures of the joint. It is believed that proprioceptive feedback provides some of the control or balance between primary and antagonistic muscle contraction. 
     In an articulating joint, a smooth and resilient surface consisting of articular cartilage covers the bony structures. In the spine, the disc, consisting of an annulus and a nucleus, spans the space between adjacent vertebral bodies and two facet joints provide articulation posteriorly. The articular surfaces of the bony structures work in concert with the soft tissue structures spanning the joint to form a mechanism that defines the envelop of motion between the structures. Within a typical envelop of motion, the bony structures move in a predetermined pattern with respect to one another. When articulated to the limits of soft tissue constraint, the motion defines a total envelop of motion between the bony structures. In the knee, the soft tissue structures spanning the joint tend to stabilize the knee from excessive translation in the joint plane of the tibiofemoral compartments. Such tibiofemoral stability enables the femur and tibia to slide and rotate on one another in an orderly fashion. The motion of the patella relative to the femur in the patellofemoral compartment is related to tibiofemoral motion because the patella is linked at a fixed distance from the tibia by the patellar ligament. 
     Current methods of preparing a joint to receive implants that replace the articular surfaces or motion segments involve an extensive surgical exposure. In traditional total knee arthroplasty, the surgical exposure, ligament release and sacrifice of the anterior cruciate ligament must be sufficient to permit the introduction of guides that are placed on, in, or attach to the femur, tibia or patella, along with cutting blocks to guide the use of saws, burrs and other milling devices, and other instruments for cutting or removing cartilage and bone to provide a support surface for implants that replace the artificial surfaces or motion segment. In traditional unicompartmental knee arthroplasty the surgical exposure may be smaller to enable access to the medial or to the lateral tibiofemoral compartment of the knee. The anterior cruciate ligament is generally preserved. For traditional knee joint replacement, the distal end of the femur may be sculpted to have flat anterior and posterior surfaces generally parallel to the length of the femur, a flat end surface generally normal to the anterior and posterior surfaces, and angled flat surfaces joining the above mentioned surfaces, all for the purpose of receiving a prosthetic device. In general these are referred to as the anterior, posterior, distal and chamfer cuts, respectively. Similarly, in traditional unicompartmental knee joint arthroplasty may be sculpted to have a flat posterior surface generally parallel to the length of the femur, a flat end surface generally normal to the posterior surface, and an angled flat surface joining the above mentioned surfaces, all for the purposes of receiving prosthetic device. 
     In current knee arthroplasty proper knee alignment is attained by preoperative planning and x-ray templating. Anterior-posterior (A/P) and lateral x-ray views are taken of the knee in full extension. The mechanical axis of the tibia and of the femur is marked on the A/P x-ray. The angle between these lines is the angle of varus/valgus deformity to be corrected. In the A/P view, the angle and depth of the distal femoral resection relative to the femoral mechanical axis, hence the angle of the femoral implant and depth of positioning into the femoral condyle, is predetermined per the surgical technique for a given implant system. Similarly, the angle of the tibial resection relative to the tibial mechanical axis, hence the angle of the tibial implant, is predetermined per the surgical technique for a given implant system. The femoral resection guides are aligned on the femur to position the distal femoral resection relative to the femoral mechanical axis and the tibial resection guides are aligned on the tibia to position the proximal tibial resection relative to the tibial mechanical axis. If the cuts are made accurately, the femoral mechanical axis and the tibial mechanical axis will align in the A/P view. Once the femur and tibia have been resected, the medial and lateral collateral ligaments may be released to balance the knee. Soft tissue balancing is generally done with the knee in full extension. The spacing between the femur and tibia at full extension is used to guide ligament release to attain an appropriate extension gap. 
     Typically, an appropriate extension gap is evidenced by parallel orientation of the distal femoral resection to the tibial plateau resection and with a gap sufficient to accommodate the femoral and tibial implants for partial or total knee arthroplasty. This approach addresses knee alignment and balancing at full extension. Knee alignment and tissue balance at 90° of flexion is generally left to surgeon judgment and knee alignment and tissue balance throughout the range of motion has not been addressed in the past. In aligning the knee at 90° the surgeon rotates the femoral component about the femoral mechanical axis to a position believed to provide proper tensioning of the ligaments spanning the knee. 
     Current implants and instruments for joint replacement surgery have numerous limitations. These relate to the invasiveness of the procedure and achieving proper alignment, soft tissue balance and kinematics of the joint with the surgical procedure. Such difficulties are present in all joint replacement surgery. Although the spinal disc is not an articular joint, interest in restoring the kinematic function of a degenerated disc has lead to spinal arthroplasty incorporating metal and/or plastic articulating surfaces. Polymers, including hydrogels and urethanes, have also been used to restore spinal disc function. Such spinal implants are preferably placed via minimally invasive surgical approaches and restore motion and kinematics, hence require accurate alignment and orientation of the implant components one to another. In addition, the kinematics of a spinal motion segment are defined by the combined motion across the disc which is a function of the annulus, nucleus, anterior ligament, posterior ligament, facet joint articulation and muscles spanning the motion segment. A spinal motion segment is the motion between adjacent vertebral bodies. 
     A difficulty with implanting modular knee implants in which the femur or tibia is resurfaced with multiple components has been achieving a correct relationship between the components. For ease of description, multiple components comprising a component such as a femoral component will be referred to as subcomponents. For example, a modular femoral component may include subcomponents for the trochlea, the lateral femoral condyle and the medial condyle, and reference to a “femoral component” includes subcomponents in the case of a multi-piece femoral component. 
     In the case of a plurality of subcomponents resurfacing the distal femur or proximal tibia, the orientation and alignment of the subcomponents to each other has largely not been addressed. This may account for the high failure rates in the surgical application of free standing compartmental replacements used individually or in combination. Such compartmental replacements include medial tibiofemoral compartment, lateral tibiofemoral compartment, patellofemoral compartment and combinations thereof. Component malalignment may account for the higher failure rate of uni-compartmental implants relative to total knee implants as demonstrated in some clinical studies. When considering bi-compartmental and tri-compartmental designs, orientation and alignment of subcomponents, as well as components, is critical to avoid accelerated wear with a mal-articulation of the implant. 
     Surgical instruments available to date have not provided trouble free use in implanting multi-part implants wherein the distal femur, proximal tibia and posterior patella are prepared for precise subcomponent-to-subcomponent and component-to-component orientation and alignment. While current femoral alignment guides aid in orienting femoral resections relative to the femur and current tibial alignment guides aid in orienting tibial resections relative to the tibia, they provide limited positioning or guidance relevant to correct subcomponent-to-subcomponent alignment or orientation. Nor do such alignment guides provide guidance relevant to soft tissue balance (i.e. ligament tension to restore soft tissue balance). Moreover, they provide limited positioning or guidance relevant to correct flexion/extension orientation of the femoral component, to correct axial rotation of the femoral component, nor to correct posterior slope of the tibial component. For the patellofemoral joint, proper tibiofemoral alignment is required to re-establish proper tracking of the patella as defined by the lateral pull of the quadriceps mechanism, the articular surface of the femoral patellar groove and maintaining the tibiofemoral joint line. For optimum knee kinematics, femoral component flexion/extension and external rotation orientation, tibial component posterior slope and ligaments spanning the joint work in concert maintaining soft tissue balance throughout the knee&#39;s range of motion. 
     For patients who require articular surface replacement, including patients whose joints are not so damaged or diseased as to require whole joint replacement, the implant systems available for the knee have unitary tri-compartmental femoral components, unitary tibial components, unitary patellar components and instrumentation that require extensive surgical exposure to perform the procedure. 
     It would be desirable to provide surgical methods and apparatuses that may be employed to gain surgical access to articulating joint surfaces, to appropriately prepare the bony structures, to provide artificial, e.g., metal, plastic, ceramic, or other suitable material for an articular bearing surface, and to close the surgical site, all without substantial damage or trauma to associated muscles, ligaments or tendons, and without extensive distraction of the joint. To attain this goal, implants and instruments are required to provide a system and method to enable articulating surfaces of the joints to be appropriately sculpted using less or minimally invasive apparatuses and procedures, and to replace the articular surfaces with implants suitable for insertion through small incisions, assembly within the confines of the joint cavity and conforming to prepared bone support surfaces. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention is related to implants and instruments for use in less and minimally invasive total knee replacement surgery. More particularly, this invention relates to instruments for cutting and preparing bone. Such bone cutting instruments are applicable in total and partial knee arthroplasty. In addition, such instruments are applicable in other total and partial joint replacement surgery to include, but not limited to the hip, the shoulder, the ankle, the elbow, the joints of the hand, the joints of the wrist, the joints of the foot and the temporal mandibular joint. Such instruments are also applicable to motion segments of the spine to include, but not limited to the spinal disc and the facet joints. For the purposes of this document, the term joint will be used to refer to articulating joints such as the knee and hip, and also motion segments of the spine. 
     The present invention provides a system and method for partial or total joint replacement to restore joint kinematics. The instruments and implants disclosed accomplish accurate bone and soft tissue preparation, restoration of anatomical alignment, soft tissue balance, kinematics, component to component orientation and alignment, subcomponent to subcomponent orientation and alignment, and implant fixation through limited surgical exposure. 
     Proper alignment and positioning of the implant components and subcomponents are enabled by instruments guided by the soft tissue structures of the knee to guide bone resections for patient-specific anatomical alignment and component orientation. The medial and lateral tibial articular surfaces and the patellar articular surface are generally prepared with planar resections. The medial and lateral femoral condyles and trochlea are kinematically prepared. Such instrumentation is referred to as Tissue Guided Surgery (TGS) and is described in U.S. Pat. No. 6,723,102 and is incorporated by reference in its entirety. 
     Proper alignment of the femoral, tibial and patellar implants requires proper anatomical alignment of the knee joint throughout the range of motion. By using the soft tissue structures spanning the knee to guide bone resection. TGS instrumentation established proper soft tissue balancing throughout the range of motion. TGS knee procedures include, but are not limited to, unicompartmental arthroplasty of the medial or lateral tibiofemoral compartments; bicompartmental arthroplasty of the patellofemoral and either the medial or lateral tibiofemoral compartment or of both tibiofemoral compartments; or tricompartmental arthroplasty of the patellofemoral joint and both tibiofemoral compartments. In such procedures, the knee joint is generally exposed through a small medial patellar incision. The anterior and posterior cruciate ligaments are left intact. Applicants believe that the instrument system will function in cases where the anterior cruciate ligament is partially or completely compromised. In one embodiment of the invention bicompartmental arthroplasty of the medial and lateral tibiofemoral compartments described herein, the medial and lateral tibial articular surfaces are removed with planar resections. Bone scribing instruments are placed on the resected surfaces in the medial and lateral tibiofemoral compartments. Each scribing instrument is extended to load against its respective condyle to score a shallow groove as the knee is flexed and extended. Primary bone sculpting instruments are then placed on the resected surfaces in the medial and lateral tibiofemoral compartments. Each primary sculpting instrument is structured to extend to distract the respective tibiofemoral compartment independent of one or more sculpting elements, such sculpting elements are then advanced into the respective femoral condyle to a depth relative to the resected tibial plateau and the knee is flexed and extended to kinematically prepare a guide surface in the femoral condyles. Secondary bone sculpting instruments are then placed on the resected surfaces in the medial and lateral tibiofemoral compartments. Each secondary sculpting instrument is structured with a guide element slidably receivable by the prepared guide surface in the respective femoral condyle. Each secondary sculpting instrument is structured to extend to distract the respective tibiofemoral compartment with a distraction force applied between the tibial plateau and the femoral guide surface applied through the guide element. In one embodiment, the secondary sculpting instrument is structured with one or more sculpting elements at a fixed distance from the guide element bearing surface such that as the knee is flexed and extended such sculpting elements prepare a surface on the respective femoral condyle at a predetermined distance from the guide surface previously prepared in the femoral condyle by the primary sculpting instrument. In another embodiment, the secondary sculpting instrument is structured with one or more sculpting elements at a variable distance from the guide element bearing surface, such sculpting elements structured to be advanced into the respective condyle to a predetermined depth relative to the guide element bearing surface. Such advancement of cutting elements is done before starting knee flexion and extension to prepare the femoral condyles. Alternatively, such advancement of cutting elements is done as the knee is flexed and extended to prepare the femoral condyles. 
     Alternatively, the knee can be positioned at specific flexion angles. At each knee flexion angle each primary sculpting instrument is structured to extend to distract the respective tibiofemoral joint independent of one or more sculpting elements. Such sculpting elements are then advanced into the respective femoral condyle to a depth relative to the resected tibial plateau to kinematically prepare a guide surface in the femoral condyles. The knee is then rotated to the next flexion angle and the process repeated. Secondary bone sculpting instruments are then placed on the resected surfaces in the medial and lateral tibiofemoral compartments. Each secondary sculpting instrument is structured with a guide element slidably receivable by the prepared guide surface in the respective femoral condyle. Each secondary sculpting instrument is structured to extend to distract the respective tibiofemoral compartment with a distraction force being applied between the tibial plateau and the femoral guide surface applied through the guide element. The secondary sculpting instrument is structured with one or more sculpting elements at a variable distance from the guide element bearing surface, such sculpting elements structured to be advanced into the respective condyle to a predetermined depth relative to the guide element bearing surface to kinematically prepare an implant support surface. Sculpting is stopped and the knee is rotated to the next flexion angle and the process repeated. Optionally, the sculpting instruments can be structured to prepare a curved, hemi-spherical or contoured surface as may be required to match various support surfaces on a mating unitary femoral implant or a femoral implant structured with a plurality of sub-components. 
     As the femoral condyles are sculpted by primary sculpting instruments, varus/valgus alignment at full extension is periodically checked. Intracompartmental distraction of the primary sculpting instrument may be biased to the medial or lateral tibiofemoral compartment for valgus or varus correction, respectively. Alternatively, primary sculpting instruments are placed in both medial and lateral tibiofemoral compartments and the respective femoral condyles are prepared simultaneously until appropriate guide surface depth is reached on one condyle. The primary sculpting instrument in this compartment is replaced with a spacer and preparation of the guide surface in the other femoral condyle is continued until anatomical align of the knee is attained. When the femoral mechanical axis and tibial mechanical axis align, the knee is properly aligned. Secondary sculpting instruments are then placed into each tibiofemoral compartment to prepare implant support surfaces in the femoral condyles as described above. Therefore, proper knee alignment and soft tissue balance is attained throughout knee range of motion. 
     In an alternative technique, each tibiofemoral compartment is prepared independently. The knee joint is exposed as described above. One of the tibiofemoral compartments is prepared first, typically the one with more severe pathology. The respective tibial articular surface is resected as described above. A bone scribing instrument, primary sculpting instrument and secondary sculpting instrument are used as described above to prepare one of the tibiofemoral compartments. Appropriately sized femoral and tibial trials are placed on the prepared bone surfaces and the other tibiofemoral compartment is prepared as described above. In the case of unicompartmental knee arthroplasty, the diseased tibiofemoral compartment is prepared with as described above for the first tibiofemoral compartment to be prepared. In the case of patellofemoral arthroplasty, the patella is resected in a planar resection, a primary sculpting instrument structured to extend to distract the patellofemoral joint independent of one or more sculpting elements, such sculpting elements are then advanced into the femoral trochlear groove to a predetermined depth below the articular surface of the trochlear groove along a path guided by patellofemoral articulation. Advancement of such sculpting elements is done after placing the primary sculpting instrument on the resected patella and before starting to flex and extend the knee. Alternatively, such advancement of sculpting elements is done while the knee is flexed and extended to create the guide surface in the femoral trochlear groove. A secondary bone sculpting instrument is placed on the resected patella. The secondary sculpting instrument structured with a guide element slidably receivable by the prepared guide surface in the trochlea. The secondary sculpting instrument is structured to extend to distract the patellofemoral joint with a distraction force applied between the patella and the trochlear guide surface applied through the guide element. In one embodiment, the secondary sculpting instrument is structured with one or more sculpting elements at a fixed distance from the guide element bearing surface such that as the knee is flexed and extended such sculpting elements prepare a surface on the trochlea at a predetermined distance from the guide surface previously prepared in the trochlea by the primary sculpting instrument. In another embodiment, the secondary sculpting instrument is structured with one or more sculpting elements at a variable distance from the guide element bearing surface, such sculpting elements structured to be advanced into the trochlea to a predetermined depth relative to the guide element bearing surface. Such advancement of cutting elements is done before starting knee flexion and extension to prepare the trochlea. Alternatively, such advancement of cutting elements is done as the knee is flexed and extended to prepare the trochlea. Patellofemoral joint and patellofemoral compartment are interchangeable terms for the patella and femoral trochlea combination. 
     For bicompartmental and tricompartmental knee arthroplasty involving the patellofemoral joint, one or both tibiofemoral compartments, whichever the case may be, are prepared as described above and trial femoral condylar and tibial components are placed to establish knee kinematics. The patellofemoral compartment is then prepared as described above. Alternatively, the patellofemoral joint is prepared as described above and trial patellar and trochlear components are placed to establish knee kinematics. One or both tibiofemoral compartments, whichever the case may be, are then prepared as described above. Optionally, in the case of tricompartmental knee arthroplasty, the femoral trochlea and both femoral condyles can be prepared at the same time by first resecting the medial and lateral tibial plateaus the patella. Then applying the scribing instruments, primary sculpting instruments and secondary sculpting instruments as described above for the patellofemoral joint and tibiofemoral compartments. Optionally, the sequence for preparing the patellofemoral joint, the medial tibiofemoral compartment and the lateral tibiofemoral compartment can be varied in any order or any combination. Alternatively, the femoral trochlea can be resected with a cutting guide placed on the distal femur or medial to the trochlea. A surgical saw, either oscillating or reciprocating, is placed on or through the cutting guide to resect the femoral trochlea. 
     Alternatively, the femoral condyles and trochlea are prepared simultaneously. The articular surfaces of the tibia and patella are removed with planar resections. Bone sculpting instruments are placed on the medial and lateral tibial resections and the patellar resection. Bone is resected from the femoral condyles and trochlea as described above. Resection depth is monitored on each condyle and the trochlea. When appropriate depth is reached in one compartment that sculpting instrument is replaced with a spacer and sculpting of remaining surfaces is continued. Once a spacer has been placed into one of the tibiofemoral compartments, resection of the other femoral condyle is continued until desired knee alignment is attained. If resection of both femoral condyles is completed before completion of the trochlear resection, the sculpting instrument in the remaining tibiofemoral compartment is replaced with a spacer and sculpting of the trochlea is continued to the appropriate depth. 
     Femoral, tibial and patellar bone resections attained with TGG instrumentation are properly positioned and orientated for anatomic knee alignment, soft tissue balance and kinematic function throughout knee range of motion. Using these bone support surfaces to position and orientate the femoral, tibial and patellar components, respectively, will maintain anatomic knee alignment, soft tissue balance and kinematic function. In general, the tibial and patellar resections are planar, making placement of the corresponding implant components, which have planar support surfaces, straight forward. The femoral resections are not planar, and the relative position of the lateral condyle, the medial condyle, and the trochlear resections to one another is a function knee kinematics for a given patient. Therefore, the femoral implant should accommodate this variability. 
     In an alternative embodiment surgical navigation is used in conjunction with TGS instrumentation to kinematically prepare the femur, tibia and patella to support knee implant components. Surgical navigation technologies applicable to this approach include, but are not limited to, image and image free navigation systems and Hall Effect based navigation systems. The knee joint is exposed as described above. Navigational trackers are attached to the femur, tibia and patella. If a tracker cannot be attached to the patella, then tracking of the patella is done periodically or at discrete points during the procedure with a tracking stylus. Pre-operative alignment and kinematics of the knee are measured per the protocol for the navigation system being used. The tibial plateau and patella are prepared as described above. Alternatively, the navigation system is used to position tibial resection guides for resection of the medial and lateral tibial articular surfaces. The navigation system may be used to align a patellar resection guide for resection of the patella. The anterior and posterior cruciate ligaments are left intact. Primary and secondary bone sculpting instruments are applied as described above as the navigation system monitors and displays femoral resection depths for the primary sculpting instruments in the patellofemoral joint and each tibiofemoral compartment throughout the range of motion while monitoring knee alignment and kinematics. The navigation system indicates when appropriate resection depth is attained on a given femoral articular surface and signals the surgeon to replace that sculpting instrument with trial implants. Femoral resection is continued until the navigation system indicates that desired knee alignment is attained. The surgical navigation system monitors trochlear resection depth and notifies the surgeon when the desired depth is attained. If appropriate trochlear resection depth is attained before completing femoral condylar resection, then trial implants can be placed in the patellofemoral compartment and femoral condylar resection continued. This technique describes using surgical navigation in conjunction with TGS instrumentation to prepare the three compartments of the knee simultaneously. In addition, surgical navigation can be used in conjunction with TGS instrumentation to prepare the knee compartments in the sequences and combinations previously described. 
     The sculpting instruments in the TGS instrumentation can be instrumented with sensors to measure intracompartmental distraction force and/or distraction distance. Such instrumentation enables monitoring of soft tissue balance during primary sculpting throughout the full range of motion. Force and/or displacement sensors can be attached to the ligaments spanning the knee as complementary measurements of soft tissue balance, distraction force and/or distraction displacement. Instrumented sculpting instruments also enable monitoring resection depth during primary sculpting and/or secondary sculpting throughout the full range of motion. Load cells are placed in a primary and/or secondary sculpting instrument to measure distraction force. Alternatively, if hydraulic pressure is used to extend the primary or secondary sculpting instrument, then pressure sensors are used to measure distraction force by multiplying pressure applied by the cross sectional area of the hydraulic actuator or bladder or balloon. Displacement sensors are placed in primary or secondary sculpting instruments to measure distraction distance. Alternatively, if hydraulics pressure is used to extend the sculpting instrument, then change in volume of fluid delivered to the hydraulic actuator or bladder or balloon by calibrating the distraction device for displacement vs. volume change. Distraction load and distraction displacement readout can be provided by digital readouts, bar graph or other graphical display. The readout can also be displayed in a surgical navigation system display. Such instrumented sculpting instruments can be used with each of the procedures and embodiments described above. Pressure to the hydraulic actuator or bladder may be provided by a syringe pump, or by a pre-charged compliant bladder designed to maintain a relatively constant pressure in the fluid over a workable change in volume required to activate the actuators or bladders used to distract the joint. Alternately, the distraction force can be applied by threaded mechanisms, inclined ramps, scissors mechanisms or other mechanical means. 
     In a more sophisticated embodiment TGS instrumentation is integrated with surgical navigation, intracompartmental distraction and displacement sensors, and programmable controllers to provide simultaneous closed loop control of the femoral resections. This application specific robotic system sculpts the femoral condyles and trochlea with primary sculpting instruments while the surgeon flexes and extends the knee. The knee joint is access as previously described. A surgical navigation system and navigation trackers are applied as previously described and pre-operative alignment and knee kinematics are measured and archived. The tibia and patella are resected as previously described. Hydraulically extended primary sculpting instruments with integral distraction force and distraction displacement sensors are placed into the three compartments of the knee. The primary sculpting instruments are applied as described above to prepare the respective femoral articular surface. Intracompartmental distraction force in each compartment can be controlled by independent closed loop controllers with distraction force as the feedback. Alternatively, distraction displacement is used for the closed loop feedback for one or more of the sculpting instruments. The robotic TGS instrument system applies a preliminary intracompartmental distraction force to the medial and lateral tibiofemoral compartments and to the patellofemoral compartment, and indicates to the surgeon that the system is ready to start femoral resection. The surgeon repeatedly flexes and extends the knee while the robotic TGS instrument system monitors primary sculpting instrument resection depth, knee alignment and knee kinematics throughout the full range of motion. The robotic TGS instrument system monitors such resection depth in each compartment to assess completion of primary sculpting in a specific compartment, at which point the system prompts the surgeon to replace that sculpting instrument with trial implants. The system then monitors knee alignment while the surgeon continues to flex and extend the knee until the navigation system indicates desired knee alignment is attained. Replacement of the patellofemoral primary sculpting instrument with a spacer is prompted by the system when a preset trochlear resection depth is attained which may occur before or after completion of condyle resections. 
     Although the application of the TGS instrumentation system to the knee is described in detail herein, it is clear that the TGS instrumentation system is applicable to other total joint arthroplasty and to spinal arthroplasty is a similar manner. The combination of TGS instrumentations with navigation and with closed loop control and robotics can have application in other joint and spinal arthroplasty applications. 
     The present invention includes methods for sculpting the articular surface of a first bone that normally articulates in a predetermined manner with a second bone. One method includes fixing one or more primary bone sculpting instruments or tools to the second bone, applying a distraction force between the two bones independent of the bone sculpting elements, sculpting a guide surface into the first bone by advancing one or more bone sculpting elements into the first bone and articulating the bones with respect to each other, fixing one or more secondary bone sculpting instruments to the second bone, slidably receiving the guide element of the secondary bone sculpting instrument in the guide surface in the first bone, applying a distraction force between the secondary bone sculpting instrument and the second bone, advancing one or more bone sculpting elements to a predetermined depth relative to the guide element, and sculpting an implant support surface into the second bone by articulating the bones with respect to each other. Optionally, sculpting the articular surface of the first bone by positioning a second bone at a specific orientation to the first bone, fixing one or more primary bone sculpting instruments to the second bone, applying a distraction force between the first and second bones independent of the bone sculpting elements, sculpting a guide surface into the first bone by advancing one or more bone sculpting elements into the first bone and articulating the bones with respect to each other, fixing one or more secondary bone sculpting instruments to the second bone, slidably receiving the guide element of the secondary bone sculpting instrument in the guide surface in the first bone, applying a distraction force between the secondary bone sculpting instrument and the second bone, advancing one or more bone sculpting elements to a predetermined depth relative to the guide element to prepare an implant support surface in the first bone. The second bone is oriented to another position relative to the first bone and the process is repeated to provide another implant support surface in the first bone. 
     Another method includes fixing one or more bone-sculpting tools to the second bone, sculpting the articular surface of the first bone by articulating the bones with respect to each other, and applying a distracting force between the bone-sculpting tool and the second bone. Optionally, sculpting the articular surface of the first bone by positioning one of the bones with respect to the other, and applying a distracting force between the bone-sculpting tool and the second bone. The distracting force is applied so as to tension the soft tissue structures spanning the knee and force the bone-sculpting tool into the first bone, in which the force applying is operated at least in part under load control. An alternative method includes fixing one or more bone-sculpting tools to the second bone, sculpting the articular surface of the first bone by articulating or positioning one of the bones with respect of the other, and applying a first distraction force between the tibia and femur so as to tension the soft tissue structures spanning the knee. With the first distraction force applied, a second distraction force, independent of the first distraction force, is applied between the bone-sculpting tool and the second bone so as to force the bone-sculpting tool into the first bone. The first distraction force is operated at least in part under load control. The second distraction force is operated at least in part under load control as material is removed from the femur, said material removal continuing until bone-sculpting tool advances to a desired orientation and position relative to the second bone. 
     In some methods, applying the distracting force includes applying a fluid under pressure, in which the load control includes controlling the fluid pressure. Controlling the fluid pressure can include controlling a gaseous fluid pressure or a liquid fluid pressure, in various embodiments. The method may include measuring the load between the two bones and controlling the distracting force at least in part as a function of the measured load. In some methods, the force applying is controlled under load control, followed by displacement control after a displacement limit is reached. The displacement control can include mechanically limiting the range of displacement. 
     In some such methods, the load control is at least in part performed by an automatic controller which automatically controls the distraction force at least in part as a function of the load. The load control may be at least in part performed under manual control, in which a human controls the distraction force at least in part in response to a load read-out value. 
     Some embodiments utilize barrel cutters. One apparatus includes a frame having a space within, an outside region without, and a plurality of cutting cylinders rotatably disposed within the frame. A drive member can be externally accessible from outside of the frame, and the drive member operably coupled to rotate the cutting cylinders. In some embodiments, the housing has a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, a right side and a left side both extending between the posterior and anterior regions, in which the drive member is a shaft which protrudes outside of the housing through the right and/or left sides. 
     In some barrel cutter embodiments, the drive member is operably coupled to the cutting cylinders through gears. In others, the drive member is operably coupled to the cutting cylinders through a flexible drive loop. In others, the drive member is operably coupled to the cutting cylinders through connecting arms. Some embodiments also include a fluid inlet port and outlet port in fluid communication with the housing interior for providing irrigation and tissue debris removal. Embodiments may also include a plurality of nested telescoping platforms, the platforms having an interior, an extended configuration and a collapsed configuration, in which the platforms can be urged from the collapsed configuration to the extended configuration through direct or indirect application of fluid pressure to the platforms interior. Some embodiments include two barrel cutter device coupled side by side in substantially the same plane, and which may be coupled to transfer applied torque between the first and second devices. In some embodiments two barrel cutters may be powered independently. 
     The present invention also provides belt cutter embodiments. One apparatus includes a frame having a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, a posterior roller rotatably coupled to the frame posterior region, an anterior roller rotatably coupled to the frame anterior region, and a cutting belt looped around both the posterior and anterior rollers. The apparatus can further include a drive member operably coupled to the anterior roller to rotatably drive the anterior roller and cutting belt. 
     In some belt cutters, the cutting belt includes a plurality of apertures therethrough, where which the apertures may optionally have a raised trailing edge. Some embodiments also include a posterior tissue protector coupled to the frame to protect tissue from the cutting belt posterior region. The belt cutter may have an anterior frame member coupled to the frame anterior portion. The drive member may be externally accessible from outside the frame, with the drive member disposed along an anterior-posterior axis, or disposed perpendicular to an anterior-posterior axis, in various embodiments. 
     Some belt cutter apparatus further include a housing base operably coupled to the frame for protecting tissue from a bottom portion of the cutting belt. A tensioning arm can be operably coupled to the anterior and posterior roller for adjusting belt tension in some embodiments. 
     Some embodiment cutting belts have a longitudinal axis, a substantially planar surface, and a plurality of outer cutting ridges disposed on the belt outer surface. The belt may have a plurality of inner ridges disposed on the belt inner surface. The ridges are oriented substantially perpendicular to the belt longitudinal axis in some embodiments, and are oriented at between about a 20 and a 70 degree angle with respect to the longitudinal axis in other embodiments. The belt may have a first set of substantially parallel cutting ridges on the belt outer surface, and a second set of substantially parallel cutting ridges on the belt outer surface, in which the first and second set of ridges cross each other to form a diamond shape pattern. In some belts, a first set of substantially parallel ridges are disposed on the belt outer surface, a second set of substantially parallel ridges are disposed on the belt outer surface, where the first and second set of ridges are disposed at least a 20 degree angle with respect to each other. Cutting belts can be tensioned and supported on rollers. A posterior tissue protector is present in some embodiment devices. Some cutting belts have a hole trailing edge that forms a grater. One cutting belt has a cutting pattern with alternating, opposing, inclined ridges partially spanning the belt. Cutting teeth can be directed anteriorly in direction of belt movement (i.e. the belt is rotating so as the superior surface is moving generally in an anterior direction) to urge the femur in an anterior direction while cutting. 
     The present invention also provides various reciprocating cutter embodiments. One such embodiment includes a frame having a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, and a substantially planar upper cutting element having a cutting surface. The apparatus also includes a drive member operably coupled to the cutter element so as to drive the cutting element to move substantially within a plane, in which the drive member is accessible from outside of the frame. In some embodiments, the drive member operable coupling is through an offset or eccentric cam. Some drive members are disposed along an anterior-posterior axis, while others are disposed orthogonal to an anterior-posterior axis, in various embodiments. Some embodiments include at least 2 upper cutting elements, each configured to operate in substantially the same plane. 
     In some reciprocating cutters, the upper cutting element cuts primarily only when moved in one direction, but not the opposite direction. In others, the upper cutting element out when moved in one direction and also in the opposite direction. Some embodiments have adjacent sub-components or sub-cutting elements 180° out of phase to each other. Some embodiments have two or more sub-cutting elements; some have four to six. 
     The present invention also provides an expandable apparatus for cutting into mammalian bone, where the apparatus can include a frame having a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, and at least one upper cutting element having a cutting surface. The apparatus also includes an extendable body operably coupled to the bottom portion, the extendable body having a first configuration, and a second configuration, in which the apparatus has a greater height in the second configuration than in the first configuration. 
     In some embodiments, the extendable body is directly coupled to the housing, while in others the extendable body is at least partially received within the housing. Some extendable bodies include a bellows. The bellows can include inward and/or outward folds. The extendable body may include a balloon or bladder received within an expandable housing having a rigid top and bottom and side panels having inward and/or outward folds. The bladder can be formed of polyethylene terephthalate (PET), nylon, polyethylene (PE), urethane, or other materials. The extendable body may include at least one leg received into the housing. The extendable body can include an expandable envelope, which may be nested within another structure. Some embodiments include at least two nested structures, one at least partially nested within the other. The nested structures can include nested, telescoping structures. The cutting element having the extendable body can include a cutting element selected from the group consisting of cutting cylinders, cutting belts, and reciprocating cutting planar surfaces. 
     A shaver cartridge apparatus is also provided by the present invention. The apparatus can include a frame having a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, and a removable cartridge. The removable cartridge can have an upper surface bearing a plurality of cutting elements, with the cartridge slidably coupled to the frame to allow for movement of the cutting elements with respect to the frame, and a drive member operably coupled to the cartridge so as to reciprocatingly drive the cartridge, where the drive member is accessible from outside of the frame. In some embodiments, the drive member is rotatably coupled to an off-center cam, where the off-center cam reciprocatingly drives the removable cartridge. The apparatus can have a protected, non-cutting posterior end region for protecting tissue. 
     The present invention also provides an apparatus for simultaneously cutting into two or more distinct regions of mammalian bone. The apparatus can include a first frame having a posterior region for inserting into a mammalian body and an anterior region opposite the posterior region, and a second frame having a posterior region for inserting into a mammalian body and an anterior region opposite the posterior region. The first and second frames can have a first and second respective moveable cutting body including an upper cutting surface capable of cutting into tissue and bone. The apparatus can include a first drive member operably coupled to the first cutting body, a second drive member operably coupled to the second cutting body, and at least one connecting member for maintaining the first and second frames in spaced apart relation to each other. 
     In some embodiments, the first and second moveable cutting bodies are each a rotating cylinder having cutting surfaces, while in other embodiments the first and second moveable cutting bodies are reciprocating cutting surfaces each bearing cutting elements. In still other embodiments, the first and second moveable cutting bodies are each closed loop belts bearing cutting elements, wherein the belts are driven by the drive members to move in a longitudinal direction. 
     Various other aspects are provided by the present invention, in various embodiments. Some devices are driven by a flexible drive belt that is a continuous loop. Some cutting surfaces have cutting teeth or abrasive material. Some cutters can expand in height using telescoping platforms. Guide posts may be used in some embodiments. The height expansion can be accomplished with a mechanical cam, screw mechanism, scissors jack, or a bladder. This may be via hydraulics in a bladder or in a piston/cylinder, via mechanical scissors, via mechanical cam, or via a spacer or shim. A stand alone telescoping or otherwise extendable section is used in some embodiments, which can be placed below or within a cutter body. In some embodiments of the present invention expand in height independent of the position of moveable cutting bodies with the moveable cutting bodies position relative to the expandable housing adjustable by height expansion mechanisms described above. 
     The present invention also provides an apparatus for cutting into two or more distinct regions of mammalian bone. The apparatus can include an expandable apparatus for cutting into mammalian bone, where the apparatus can include a frame having a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, and at least one upper cutting element having a cutting surface, and a standalone telescoping or otherwise extendable apparatus having a posterior region for inserting into a mammalian body, an anterior region opposite the posterior region, and at least one extendable body. The cutting apparatus is placed in a first distinct region of mammalian bone. The telescoping section is placed in a second distinct region of mammalian bone. The apparatus can include a drive member operably coupled to the cutting apparatus, and optionally at least one connecting member for maintaining the cutting apparatus in spaced apart relation to the telescoping apparatus. In some embodiments, the telescoping section includes one or more extendable bodies. The telescoping section can have an extendable body directly coupled to the housing, while in others the extendable body is at least partially received within the housing. The extendable body having a first configuration, and a second configuration, in which the apparatus has a greater height in the second configuration than in the first configuration. In one embodiment at least one cutting element moves along with the extendable body. In another embodiment at least one cutting element is stationary with the base housing with the extendable body moving independently of at least one cutting element. 
     Some cutters are made primarily from stainless steel. The frame and housing can be made of suitable plastics, such as Polyetheretherketone (PEEK). 
     Unless otherwise noted, some embodiments of the barrel cutter, reciprocating, and belt cutter devices according to the present invention can have a frame length of between about 10 mm and 90 mm, and a width of between about 10 mm and 50 mm. Others have a frame length of between about 10 mm and 90 mm, and a width of between about 40 mm and 100 mm. Still others may have a frame length of less than about 10 cm and a width of less than 10 cm. Yet others may have a frame length of less than about 2 cm and a width of less than about 1 cm. 
     Unless otherwise noted, some embodiments of the barrel cutter, reciprocating, and belt cutter devices according to the present invention can be used by operating two or more cutters at the same time. One cutter can be placed in the medial tibiofemoral compartment and one placed in the lateral tibiofemoral compartment. One cutter may be placed in the patellofemoral compartment as well. Any combination of these may be used. The cutters may have a common drive member, or they may have individual drive members. They can be distracted independently, or be distracted (i.e. deployed) as a set. They can be distracted with at least one cutting element maintaining a constant distance from the base of the cutter, or be distracted with at least one cutting element maintaining a constant distance from the leading surface of the extendable housing of the cutter. Each may be deployed under “load” control or under “displacement” control, or a combination thereof. Each may be initially deployed under “load” control, then changed to “displacement” control, or visa versa. As they deploy, the frame may constrain the cutting elements in a plane parallel to the base of the frame, or allow the plane of the cutting elements to angulate relative to the base of the frame. The frame may be integral with the base of the cutter or it may be integral with the extendable housing of the cutter. 
     Surgical Procedure 
     The surgical procedure involves exposing the diseased tibiofemoral compartment through a small, vertical incision without disrupting muscle structure, or everting or dislocating the patella. The diseased tibial plateau is removed with a conventional tibial resection guide and oscillating and/or sagittal bone saw(s). A primary femoral cutter, referred to as a primary sculpting instrument herein, is placed onto the resected tibial plateau and vertically expanded under load control to tension the joint space. The cutting elements, referred to as sculpting elements herein, are then activated and advanced into the femoral condyle while the surgeon flexes and extends the knee. As the knee joint is flexed the cutter appropriately cuts the articular surface of the femur in a manner that is dependent upon the individual physiology of the patient&#39;s knee as established by the patient&#39;s cruciate and collateral ligaments, patellar tendon, and soft tissue structures spanning the knee joint. The cutter expands to a height greater than the combined thickness of the intended tibial and femoral implants. As a result, a guide surface (referred to as “SGG” or “groove” in US Provisional Application add number) is created in the femoral condyle; the ceiling of which represents a kinematically correct reference position for the femoral implant. The primary sculpting instrument is removed and replaced with a secondary femoral cutter, referred to as a secondary sculpting instrument herein. Sculpting of the remaining femoral condyle by the secondary sculpting instrument is guided by this groove. 
     The secondary sculpting instrument is structured to distract the joint space thereby providing alignment, stability and uniform kinematic motion as a function of the cruciate and collateral ligaments. Distraction is provided by a telescoping between the base of the cutter and the resected tibial plateau. The Guide Bar, referred to as a guide element herein, rests against the ceiling of the prepared guide surface. Bone is removed from the condyle on either side of the guide surface to a predetermined depth below the ceiling of the groove, which is the guide surface, previously prepared in the femoral condyle. The result is a kinematically prepared bony support surface for the condylar implant that allows for the combined thickness of the femoral and tibial implants within the joint space. A partial depth of the guide surface remains to expose trabecular bone for bone cement interdigitation and space for a sagittal fin on the condylar component for cement fixation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a barrel cutter having transversely mounted rotatable cylindrical cutting elements, irrigation ports, and a drive shaft. 
         FIG. 2  is a perspective view of a cylindrical cutting element having a central drive recess suitable for use in some string driven barrel cutters, for example, that of  FIG. 12 . 
         FIG. 3  is a perspective view of another cylindrical cutting element suitable for use in some end driven barrel cutters, for example, that of  FIG. 1 . 
         FIG. 4  is a perspective view of a reciprocating cutter having an upper, substantially planar cutting element. 
         FIG. 5  is an exploded view of the reciprocating cutter of  FIG. 4 , showing the irrigation ports and the reciprocating drive shaft mechanism. 
         FIG. 6  is a perspective view of the barrel cutter of  FIG. 1 . 
         FIG. 7  is a top, cross-sectional view, taken through the cutting element centers, of the barrel cutter of  FIG. 1 , showing the bevel gear drive for driving the barrel cutters. 
         FIG. 8  is a side, cross-sectional view, taken though the drive gears, of the barrel cutter of  FIG. 1 , showing the end driven cutter elements and gear drive train. 
         FIG. 9  is a top, schematic view of the barrel cutter of  FIG. 1 . 
         FIG. 10  is a side, elevation view of the barrel cutter of  FIG. 1 . 
         FIG. 11  is an exploded view of the barrel cutter of  FIG. 1 . 
         FIG. 12  is a perspective view of a string driven barrel cutter having a bottom telescoping platform, a side drive shaft, and which can use the cutter element of  FIG. 2 . 
         FIG. 13  is a side, cross-sectional view of the string driven barrel cutter of  FIG. 12 , taken through the drive loop. 
         FIG. 14  is an exploded view of the string driven barrel cutter of  FIG. 12 . 
         FIG. 15  is a perspective view of the string driven barrel cutter of  FIG. 12 , shown in a collapsed configuration. 
         FIG. 16  is a side, cross-sectional view of the string driven barrel cutter of  FIG. 12 , taken through the drive loop, shown in an expanded telescope configuration. 
         FIG. 17  is an exploded view of the string driven barrel cutter of  FIG. 12 , with the telescoping platforms shown in an expanded, configuration. 
         FIG. 18  is a perspective view of a belt cutter having a linear tensioning frame using a screw mechanism to tension the cutting belt. 
         FIG. 19  is an exploded view of the belt cutter of  FIG. 18  having a linear tensioning frame. 
         FIG. 20  is an exploded view of another belt cutter, having a hinge tensioning frame using a scissors mechanism to tension the cutting belt. 
         FIG. 21  is a perspective view of a reciprocating cutter having a substantially planar upper cutting element and a side drive shaft. 
         FIG. 22  is an exploded view of the reciprocating cutter of  FIG. 21 , showing irrigation ports and plenum, and an off-set cam reciprocating mechanism within. 
         FIG. 23  is perspective view of an expandable telescoping bladder, shown in a collapsed configuration. 
         FIG. 24  is a perspective view of an expandable housing, suitable for receiving the bladder of  FIG. 23  within. 
         FIG. 25  is a perspective, cutaway view, and a non-cutaway view, of the bladder of  FIG. 23  disposed within the platform of  FIG. 24 , shown in a collapsed configuration. 
         FIG. 26  is a perspective, cutaway view, and a non-cutaway view, of the bladder of  FIG. 23  disposed within the platform of  FIG. 24 , shown in an expanded configuration. 
         FIG. 27  is a perspective view of a dual belt cutter positioned in the knee joint. 
         FIG. 28  is a perspective view of a belt cutter. 
         FIG. 29  is a perspective view of a knee joint with the tibial plateaus resected. 
         FIG. 30  is a lateral side view of the knee with a telescoping cutter positioned in the lateral tibiofemoral joint. 
         FIG. 31  is a medial side view of the knee with a telescoping cutter positioned in the medial tibiofemoral joint. 
         FIG. 32  is lateral side view of the knee with a telescoping cutter positioned in the patellofemoral joint. 
         FIG. 33  is a schematic top view of a reciprocating drive top cutting element and drive shaft. 
         FIG. 34  is a perspective view of dual barrel cutters, which can be similar to the barrel cutters of  FIG. 12 , shown in position in the tibiofemoral compartments. 
         FIG. 35  is a perspective view of dual barrel cutters, for example the barrel cutters of  FIG. 12 . 
         FIG. 36  is a perspective view of dual reciprocating cutters shown in position in the tibiofemoral compartments. 
         FIG. 37  is a perspective view of dual barrel cutters positioned in the knee joint. 
         FIG. 38  is a perspective view of dual belt cutters, for example the belt cutters of  FIG. 20 , shown in position in the tibiofemoral compartments. 
         FIG. 39  is a perspective view of dual belt cutters, for example the belt cutters of  FIG. 20 . 
         FIG. 40  is an end elevation view of a reciprocating cutter, having the telescoping platform in an extended configuration. 
         FIG. 41  is an end elevation view of the reciprocating cutter of  FIG. 40 , having the telescoping platform in a retracted or collapsed configuration. 
         FIG. 42  is an exploded view of the reciprocating cutter of  FIG. 40 , showing the retainer for securing the top cutting element. 
         FIG. 43  includes orthogonal views and a perspective view of a cutting belt. 
         FIG. 44  includes orthogonal views of a cutting belt. 
         FIG. 45  includes orthogonal views of a cutting belt. 
         FIG. 46  includes orthogonal views of a cutting belt. 
         FIG. 47  includes perspective views of a cartridge for use in removing bone. 
         FIG. 48  includes exploded views of the cartridge of  FIG. 47 . 
         FIG. 49  is an exploded view of a bone scribing instrument showing a serial distractor, a scribing insert with longitudinal rasping element and a tibial trial base. 
         FIG. 50  is a perspective view of a bone scribing instrument assembled with a tibial trial base and the spring loaded distraction platform retracted. 
         FIG. 51  is an illustration of a surgically exposed knee with the medial femoral condyle visible showing a bone scribing instrument in place and a line scribed into the femoral condyle. 
         FIG. 52  is an exploded view of a primary sculpting instrument showing a longitudinal sculpting element and a distal spring loaded distraction platform. 
         FIG. 53  a perspective view of a primary sculpting instrument of  FIG. 52  showing the distal distraction platform retracted. 
         FIG. 54  is a perspective view of the primary sculpting instrument of  FIG. 53  showing the distraction platform released and extended. 
         FIG. 55  is an illustration of a surgically exposed knee with the medial femoral condyle visible showing a primary sculpting instrument in place and a prepared guide surface in the medial femoral condyle. 
         FIG. 56  is an exploded view of a sculpting element and drive motor assembly of the primary sculpting instrument of  FIG. 52 ,  FIG. 53 ,  FIG. 54 ,  FIG. 59 ,  FIG. 60 ,  FIG. 61  and  FIG. 63 , showing a motor, a sculpting element and collet locking mechanism. 
         FIG. 57  is an exploded view of the scribing insert of  FIG. 49  and  FIG. 50 . 
         FIG. 58  is an exploded view of the serial distractor shown in  FIG. 49 ,  FIG. 50 ,  FIG. 52  and  FIG. 53 . 
         FIG. 59  is a primary sculpting instrument with a parallel distractor and tibial trial base. 
         FIG. 60  is an exploded view of the primary sculpting instrument of  FIG. 59 . 
         FIG. 61  is a side view of the primary sculpting instrument of  FIG. 59  showing the distraction platform collapsed. 
         FIG. 62  is a cross sectional view of the parallel distractor of  FIG. 61  taken through a mid-section showing the distraction platform in a collapsed position and the springs providing distraction force. 
         FIG. 63  is a side view of the primary sculpting instrument of  FIG. 59  showing the distraction platform extended. 
         FIG. 64  is a cross sectional view of the parallel distractor, motor and tibial trial base of  FIG. 63  taken through a mid-section showing the distraction platform in an extended position and the springs providing distraction force. 
         FIG. 65  is an exploded view of the parallel distractor of  FIG. 59 . 
         FIG. 66  is a perspective view of another embodiment of a parallel distractor showing a dished distraction platform for use in a primary sculpting instrument. 
         FIG. 67  is a perspective view of a secondary sculpting instrument showing barrel sculpting elements with adjacent sculpting elements rotating in opposite directions. 
         FIG. 68  is cross sectional view of the secondary sculpting instrument of  FIG. 67  taken along the center of the guide element showing a spline gear drive train of the secondary sculpting instrument. 
         FIG. 69  is an exploded view of the secondary sculpting instrument of  FIG. 67 . 
         FIG. 70  is a perspective view of another embodiment of a secondary sculpting instrument showing barrel sculpting elements with adjacent sculpting elements rotating in the same direction. 
         FIG. 71  is cross sectional view of the secondary sculpting instrument of  FIG. 70  taken along the center of the guide element showing a crankshaft and connecting arm drive train of the secondary sculpting instrument. 
         FIG. 72  is an exploded view of the secondary sculpting instrument of  FIG. 71 . 
         FIG. 73  is an illustration of a surgically exposed knee with the medial femoral condyle visible showing a secondary sculpting instrument in place and a prepared implant support surface in the medial femoral condyle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Some embodiments of the invention include replacing the articulating surfaces of the knee with implants. Supporting information is included in current patents and patent applications, to include U.S. Pat. No. 6,482,209 and U.S. Pat. No. 6,723,102, herein incorporated by reference. 
     The present application includes disclosure of bone scribing instruments, primary sculpting instruments and secondary sculpting instruments for preparing the femoral condyles and trochlea. Various embodiments of each are presented. Sculpting instruments, sculpting instrumentation, sculpting devices, sculpting apparatus and bone-sculpting tools are interchangeable terms. It should be noted that tissue guided surgery and the sculpting device embodiments are applicable to other joints in the body, to include but not limited to the hip, shoulder, ankle; and motion segments of the spine, to include the disc and facet joints. The femoral cutter (sculpting devices) described herein include a shaver (as initially described in U.S. Pat. No. 6,428,209), a barrel cutter, a reciprocating cutter and a belt cutter. Various embodiments of each are presented. 
       FIG. 1  illustrates a barrel cutter designed with multiple cylindrical cutting elements  103 . The barrel cutter can be designed with one or more cutting elements  103 . In one embodiment the barrel cutter is designed with five cutting elements  200  (as shown in  FIG. 12 ). 
     The area of contact between the bony surfaces of the tibiofemoral and patellofemoral compartments moves along the surface of the femur, within each compartment, as the knee flexes and extends. This movement is greater on the lateral side due to rotation of the tibia. Hence, it is desirable to have a cutting surface sized to remove bone as the location of the contact area moves over the surface of the femur. In one embodiment the cutting elements  103  are small in diameter and spaced closely together. The overall cutting surface area as shown in  FIG. 1  has a cutting surface length  108 , a cutting surface width  109 , and is sized to accommodate the movement of the medial or lateral tibiofemoral contact area during knee flexion and extension and the width of the medial or lateral femoral condyle. In general, in some embodiments, the cutting surface length may range from approximately 10 mm to 90 mm and the cutting surface width may range from 10 mm to 50 mm, for cutters designed to be placed in either tibiofemoral compartment. In another embodiment in which the tibial plateau is resected, the cutting surface width matches that of the mediolateral width of the distal femur, which may range from approximately 40 mm to 100 mm. 
       FIGS. 1 ,  6 ,  7 ,  8 ,  9  and  10 , illustrate one embodiment of a barrel cutter, in which the cutting elements  103  are supported by a cutter housing  107  and a side plate  102 . Cutter housing  107  is separated from drive housing  101  by spacer plate  111 , and from side plate  102  by spacer plate  110 . Side plate  102  can be secured using fasteners  1000  (shown in  FIG. 10 ). Side plate  102  can also include top attachment holes  900  (shown in  FIG. 9 ). Optionally, two barrel cutters can be used simultaneously to prepare the medial and lateral femoral condyles. In a left knee the shown barrel cutter is placed in the medial tibiofemoral compartment. A barrel cutter (not shown) structured as the mirror image of the barrel cutter shown is placed in the lateral tibiofemoral compartment. Each barrel cutter structured with four attachment holes  900  to which a cross bar (not shown) can be attached with threaded fasteners (not shown) to stabilize and orient one barrel cutter to the other. Alternatively, each barrel cutter can be placed in respective tibiofemoral compartments independently without connecting them together. 
     The drive housing  101  supports a drive shaft  100 . A rigid or flexible drive shaft extension (not shown) can be attached between the drive shaft  100  and a rotational power supply, such as a surgical power drill or a motor.  FIG. 7  illustrates how input torque can be delivered to drive shaft  100  which is attached to a bevel gear set  700  and  701  (or bevel gears  1100  and  1101  in  FIG. 11 ).  FIG. 8  illustrates how torque is transferred to drive gear  805  by shaft  702 . From the cutter drive gear  800 , torque is transferred to a transfer gear  804  to a cutter drive gear  800 . Idler gears  803  are placed between subsequent cutter drive gears  800  to transfer torque to each of the cutting elements  103 . A lock pin  802  is placed into gear relief  801  and relief  303  to secure the gear to the cutter. In one embodiment, the cutter drive gears  800  are pinned to the cutter hub  302  (shown in  FIG. 3 ). Referring to  FIGS. 8 and 11 , the barrel cutter is structured to drive cutting elements  103  with drive shaft  100  connected to bevel gear  1100 . Bevel gear  1100  meshed with bevel gear  1101  which is connected to shaft  1105  which is connected to drive gear  805  which meshes with transfer gear  804 . Transfer gear  804  meshes with cutter drive gear  800  which meshes with idler gear  803  and torque is transferred to each cutting element via idler gear  803  and drive gear  800  combinations. Transfer gear  804  and idler gears  803  are supported by shafts  1109 . Shafts  1109  passing through and supported by clearance hole  1114  in side plate  102  and clearance hole  1115  in face plate  1102 . Face plate  102  is assembled with cutter housing  107  by threaded fasteners (not shown) passing through clearance holes  1116  in side plate  102 , clearance holes  1117  in face plate  1102  and into threaded holes  1106  in cutter housing  107 . 
       FIG. 3  illustrates that cutting element  103  has one or more cutting edges  106 , and in one embodiment there are four cutting edges  106  as shown in  FIG. 3 . Cutting element  103  is supported on one end by a hub  301  and at the other end by a gear hub  302 . A cutter relief  300  is designed trailing the cutting edge  106  to enhance cutting. 
       FIGS. 1 ,  6  and  11  illustrate features which beneficially flush bone debris out of the femoral cutter during operation. Sterile saline or other suitable fluid may be used for this purpose. The barrel cutter is designed with input port  104  and output port  105 . Irrigation fluid is delivered to the barrel cutter by a plastic tube (not shown) structured to attach to the barrel cutter at port  104  to be channeled through housing  101 , through face plate  1103  via irrigation input port  1107 , into channel  1104  leading to longitudinal hole  1111  in communication with each cutting element  103  relief channel  1112 . Irrigation fluid flows over cutting element  103  to be gathered in longitudinal hole  1113  in communication therewith. Irrigation fluid flowing through face plate  1103  via irrigation output port  1108  in communication with port  105  in housing  101  and into a plastic tube (not shown) structured to attach to housing  101 . 
     Durability, sharpness and cleanability are important for the function and use of the femoral cutter. Given the small size of the femoral cutters, a single use device is preferred to provide sharp cutting elements in each surgical case and to ensure durability of the device. Cost is an important factor in single use devices. The use of gears to drive the cutting elements is costly for two reasons, the cost of the gears and the cost of machining to hold tolerances for proper function of the gears. Hence, a less expensive drive means would be desirable. 
       FIG. 13  illustrates another embodiment of a barrel cutter, in which a string drive is used to drive each of the cutting elements. The string drive can be a continuous loop that is wrapped around each cutter and around an input shaft so that as the input shaft is rotated, each cutting element rotates. The string drive is designed with a drive loop  1300 , which may be a monofilament string, multi-strand woven string or cord; single or multi-strand wire; drive belt, V-belt or timing belt; or other flexible band that can be placed around or on the cutting elements to impart rotation. The drive loop  1300  is wrapped around a drive shaft  1202  one time as shown, or in another embodiment multiple times (not shown) to take advantage of the increased friction between the drive loop and shaft with multiple windings. 
     The drive loop  1300  can be wrapped one or more times around each cutting element  200 . 
       FIG. 2  illustrates a cutting element  200  designed with a recess  203  for receiving drive loop  1300 . The cutting element can be supported by hubs  201 . Cutting element  200  includes cutting edges  202 , and chip relief  204 , formed as a circumferential groove in this embodiment. Cutting element  200  is structured with one or more cutting edges  202 . Each cutting edge  202  is structured with one or more chip relief&#39;s  204  that improve cutting element&#39;s  200  chopping of articular cartilage present on the femoral condyle and in chopping bone to be removed.  FIGS. 12 ,  13  and  14  illustrate an embodiment in which the string drive is integral to the femoral cutter. Drive shaft  1202  and cutting elements  200  are supported by a common housing  1200  and  1201 , and a means for tensioning the loop drive  1300  is provided. Common housings  1200  and  1201  are held in alignment by alignment pins  1301  slidably received in holes  1400 . Common housings  1200  and  1201  structured to be adhesively bonded together between common faces  1404  and  1405 . In another embodiment (not shown) the drive shaft is supported in a separate housing and one or two flexible tubes connect the drive shaft housing to the cutting element housing. In an embodiment using one flexible tube the dive loop is wrapped around the drive shaft one or more times and passed through the flexible tube into the cutter housing wherein the loop drive is wrapped one or more times around each cutting element. In an embodiment using two flexible tubes, the drive loop would be an open loop in which the string is passed through one tube, into the cutting element housing, wrapped one or more times around each cutting element, routed out of the cutting element housing, through the second tube, into the drive shaft housing, then wrapped one or times around the drive shaft and connected to the other end of the drive loop. Alternatively, for the single or dual tube embodiments, the flexible tube may be rigid and made of steel, plastic or other suitable material. 
       FIG. 14  illustrates an embodiment in which drive shaft  1202  is designed with ridges  1401  and  1402  and a groove  1403  to guide drive loop  1300 . The opposing faces  1404  and  1405  of the housing can be brought together over alignment pins  1301  inserted into holes  1400 . 
     As described above, it is beneficial to expand the cutters within the patellofemoral compartment and tibiofemoral compartments. The barrel cutter is designed with a cylinder to provide axial expansion of the cutter.  FIG. 13  illustrates that the cylinder may be of multiple stages as shown by telescoping platforms  1302 ,  1303  and  1304 , which are held in place within housing  1200  and  1201  with telescoping platform  1203 .  FIG. 13  shows the cylinder in a collapsed position.  FIGS. 15 ,  16  and  17  show the cylinder in an extended position. 
       FIGS. 4 and 5  illustrate a reciprocating cutter designed to be placed in either the tibiofemoral compartment and/or in the patellofemoral compartment. Cutting element  400  is designed with cutting teeth on top surface  500 . The cutting teeth may be continuous from side to side or include individual cutters staggered over the surface of the cutting element so as to provide uniform material removal over the surface of the cutting element. Alternatively, the top surface may have an abrasive texture to remove material. In either case, the surface of the cutting element may be continuous or may have holes to allow material removed from the femur to pass through. 
     Cutting element  400  is driven in a reciprocating fashion by applying torque to drive shaft  404 . Torque may be supplied by a surgical power drill or a motor. A flexible or solid drive shaft can be used to connect the surgical power drill or motor to drive shaft  404 . A reciprocating drive groove  506  is formed by an upper boss  505  and a lower boss  504 , and having an upper groove wall  507  and a lower groove wall  508 . As the drive shaft spins, reciprocating drive groove  506  imparts a reciprocating motion to cutting element  400 . A hub  502  rides within reciprocating drive groove  506  and moves in an axial direction to drive cutting element  400  via cutter arm  501 . Drive shaft  404  includes an end hub  509  which is received in hub support  511  adjacent a reciprocating drive recess  510  and a drive shaft recess  512 . Distal end of drive shaft  404  is structured with hub  509  to align and support distal end of drive shaft  404 . Drive shaft  404  is supported in drive housing  402  and drive cover  401  each structured with hub support  511  to support distal end of drive shaft  404  and drive shaft support  512  to support drive shaft  404 . Clearance for lower boss  504  and upper boss  505  within drive housing  402  and drive cover  401  is provided by recess  510 .  FIG. 33  illustrates that cam  3302  rides in the groove  3306  between bosses  3304  and  3305  while drive shaft  3303  rotates, resulting in a reciprocating motion of arm  3301  and cutting element  3300 . Cutting element  400  is supported by drive housing  402 . Drive shaft  404  and cutter arm  501  are held in relative position by drive housing  402  and enclosed by drive cover  401 . 
       FIGS. 40 ,  41 , and  42  show that as cutting element  400  reciprocates, the posterior aspect of the cutting element  400  is beneficially guided and cutting element  400  is retained on the surface of the drive housing  402 . A retainer  4000  is visible on the underside of cutting element  400 . The retainer  4000  fits into cavity  4200  and is held vertically by a shoulder  4201  fitting into a groove  4202 . The cavity is elongated to allow reciprocating motion of the cutter element  400 . 
       FIGS. 21 and 22  illustrate an alternate embodiment having a cutting element  2100  structured to be supported on housing base  2101 . Said housing  2101  base structured to support drive shaft  2104  and enclose said drive shaft  2104  with housing cap  2103 . Drive shaft  2104  structured to oscillate cutting element  2100 . Offset cam  2200  is in communication with channel  2205  in cutting element  2100  arm  2206 . Housing base  2101  is structured with chamber  2214  to provide clearance for drive shaft  2104  bosses  2201  and  2202 . Drive shaft  2104  cylinder  2204  is slidably received in channel  2203  in housing base and in adjoining channel (not shown) in housing cap  2103 . Bosses  2201  and  2202  capture said channel  2203  to slidably retain drive shaft  2104 . As drive shaft  2104  rotates, cam  2200  rotates and slides within channel  2104  thereby moving cutting element back and forth within bosses  2215  protruding from housing base  2101 . Cutting surface  2207  structured to remove tissue when oscillated against adjoining bone. Cutting surface structure includes embodiments described here in, to include ridges, grit surface, protuberances, or other suitable cutting feature known to those skilled in the art. Reciprocating cutter is structured to telescope. Telescoping platform  2102  is structured to slidably assemble with housing base  2101 . Guide posts  2208  are slidably received in holes  2210 . The leading end of guide posts  2208  are structured with snap retainers  2209  that engage lips  2216  within holes  2210 . Tissue removed from the femur flows into chamber  2211 . Input hole  2212  is structured to attachably receive a tube (not shown) through which irrigation fluid flows into chamber  2211 . Irrigation fluid is transported out of chamber  2211  through output hole  2213 . Said output hole  2213  structure to attachably receive a tube (not shown) which may be connected to a vacuum system (not shown). 
       FIG. 5  illustrates that a port  515  brings irrigation fluid, e.g. sterile saline, into a cavity  514  behind cutting element  400  via opening  518 . The fluid exits the cavity via opening  519  and port  516 . As mentioned earlier, it is beneficial to wash debris from femoral resections away from the cutter. 
       FIGS. 4 and 5  illustrate a reciprocating cutter which can expand. A telescoping platform  403  is provided on the base of the cutter. Guide posts  503  align the telescoping platform  403  and limit travel by snap-in retainers  517 . Guide posts  503  are designed to fit into and snap into receiving holes  513  in the drive housing  402 . 
       FIG. 41  illustrates the reciprocating cutter in a fully collapsed position. The collapsed reciprocating cutter fits easily into a tibiofemoral compartment, or into the patellofemoral compartment. To tension the ligaments and capsule the reciprocating cutter can be expanded as shown in  FIG. 40 . Expansion of the telescoping platform may be accomplished by a mechanical cam, screw mechanism or scissors jack (not shown), or by a bladder. Bladder designs are described below. 
       FIG. 18  illustrates yet another embodiment, a femoral cutter having a cutting belt  1800 . Cutting belt  1800  is supported on a frame and driven to move the cutting surface across the adjacent femoral condyle or trochlea. Cutting belt  1800  can be tensioned and supported on rollers. Torque is applied to the drive shaft  1803  by a surgical drill or motor with a flexible or rigid drive shaft as previously described. As the belt cutter is placed into a tibiofemoral compartment and operated, the tissue structures in the back of the knee need to be protected. A tissue protector  1804  is designed as part of the housing base  1801  for this purpose. A housing end cap  1805  may be seen at the anterior end. 
       FIG. 19  illustrates the femoral cutter of  FIG. 18  in an exploded view. Cutting belt  1800  is supported on an idler roller  1906  having a shaft  1907  received within, and a drive roller  1903  having a drive shaft cylinder  1904  received within. Hole  1922  through idler roller  1906  snuggly receives shaft  1907  structured to press fit shaft  1907  in hole  1922 . Tensioning arm  1900  is structured with tabs  1916  protruding from distal end through which holes  1913  pass. Idler roller  1906  is positioned between tabs  1916  and shaft  1907  is slidably received through first hole  1913 , press fit through hole  1922  in idler roller  1906 , and slidably received in second hole  1913 . As for the drive roller  1903 , housing frame  1802  and housing end cap  1805  adjoin along interface  1807 . Hole  1912  extends along interface  1807  and slidably receives drive shaft  1803 . Hole  1905  through drive roller  1903  snuggly receives drive shaft  1803  structured to press fit drive shaft  1803  in hole  1905 . Drive shaft  1803  is press fit into hole  1905 . Boss  1915  protruding from housing frame  1802  is slidably received in channel  1914  in housing frame  1802 . Screws  1908  are assembled in threaded holes  1909  in housing frame  1802 . Assembled drive roller  1903  and drive shaft  1803  are slidably received by the portion of hole  1912  formed in housing frame  1802 . Skid  1902  is placed on said assembly and the combination placed inside cutting belt  1800  with said cutting belt positioned between bosses  1808  protruding from housing frame  1802 . Screws  1908  are advanced to properly tension cutting belt  1800 . Drive shaft  1803  is secured by the portion of hole  1912  formed in housing end cap  1804 . Housing end cap  1804  is assembled to housing frame with threaded fasteners (not shown) slidably received through holes  1917  and threaded into receiving holes (not shown) in housing frame  1802 . Skid  1901  is placed inside housing base  1801  and combination is placed onto assembled cutting belt  1800 , housing frame  1802  and housing end cap  1805 . Housing base  1801  is assembled to tensioning arm  1900  with threaded fasteners (not shown) slidably received through holes  1919  in tabs  1918  protruding from housing base  1801 . Said screws treadably received in threaded holes  1920  in tensioning arm  1900 . Hole  1921  in housing frame  1802  is structured to attachably receive a plastic tube to which operating room suction is applied to remove fluid and tissue debris from tissue and bone cutting. 
     As the cutting surface  1806  of cutting belt  1800  works against the femoral condyle or trochlea, compressive force is carried by a skid  1902  below the belt and structural support is provided to the frame by a second skid  1901 . Tissue is removed by one or more protuberances  1923  structured in the cutting belt  1800 . Such protuberances  1923  formed by stamping or pressing a form into cutting belt  1800 , or by attaching a formed or machined protuberance to the cutting belt  1800 . Such attachment by adhesive, welding, diffusion bonding, press fit or other attachable means know in the art. Cutting belt  1800  is fabricated from stainless steel, cobalt chromium molybdenum alloy, or other suitable metal. Alternatively, cutting belt  1800  may be fabricated from rubber, urethane, or other suitable polymeric material with embedded protuberances as described above. Optionally, said polymeric cutting belt may be reinforced by fibers, metal mesh or other suitable material to increase strength and durability. A polymeric cutting belt can have integral metal cutting elements with protuberances. Alternatively, the metal cutting elements can be abrasive. To tension the cutting belt  1800 , the housing frame  1802  is adjustable by turning two screws  1908  to advance a tensioning arm  1900  to increase tension on the belt cutter. The belt is driven in the direction shown in  FIG. 19  by applying torque to the drive shaft  1803  which is attached to the drive roller  1903 . The belt slides across upper skid  1902  and lower skid  1901 , and turns on an idler roller  1906 . A surgical drill, or a motor, with a flexible drive shaft as previously described can be used to apply torque to the drive shaft  1803 . 
     To remove material from the femur, the cutting belt  1800  is designed with holes  1910  that create a rough edge when run against the femur. Alternately, the trailing edge  1911  of the hole  1800  is elevated to form a grater for more aggressive cartilage and bone removal (see the belt detail in  FIG. 19 ). The cutting belt is formed by cutting or stamping the hole pattern in a strip of metal or other suitable material and welding or bonding the ends together to form a belt. Alternatively, the outer surface of belt  1800  can be abrasive. 
       FIGS. 43 ,  44  and  45  illustrate alternate cutting belt embodiments fabricated from a strip that is welded or bonded (e.g. at  5307 ) into a belt or loop. In an alternate embodiment, a cutting pattern is chemically etched, stamped or machined into the outer surface of the cutting belt. As shown in  FIG. 43 , ridges  5302  are formed into the outer surface  5300  of the cutting belt. The outer ridge pattern  5302  is perpendicular to the side  5303  of the belt. The inner surface  5301  may have a pattern chemically etched, stamped or machined in it to enhance traction with the drive roller described above, or the inner surface may be smooth or roughened. The inner ridge pattern  5304  is perpendicular to the side  5303  of the belt. The belt is formed into a loop and the fastening edges  5305  and  5306  are welded or bonded together. 
       FIG. 44  shows an alternate embodiment, in which a cutting pattern is chemically etched, stamped or machined into the outer surface of the cutting belt. Ridges  5402  are formed into the outer surface  5400  of the cutting belt. The outer ridge pattern  5402  is inclined relative to the side  5403  of the belt. The inner surface  5401  may have a pattern chemically etched, stamped or machined in it to enhance traction with the drive roller described above, or the inner surface may be smooth or roughened. The inner ridge pattern  5404  is inclined relative to the side  5403  of the belt. The belt is formed into a loop and the fastening edges  5405  and  5406  are welded or bonded together. 
       FIG. 45  shows an alternate embodiment belt having a side  5503 , in which belt a cutting pattern is chemically etched, stamped or machined into the outer surface of the cutting belt. Alternatively, the outer surface of belt can be abrasive. Abrasive surface, as used herein, formed by grit blasting, plasma spray, bonding abrasive material, or other fabrication method known to one skilled in the art. Ridges  5502  are formed into the outer surface  5500  of the cutting belt. The outer ridge pattern  5502  is alternating, opposing, inclined ridges partially spanning the belt. The inner surface  5501  may have a pattern chemically etched, stamped or machined in it to enhance traction with the drive roller described above, or the inner surface may be smooth or roughened. The inner ridge pattern  5504  is a diamond pattern. The belt is formed into a loop and the fastening edges  5505  and  5506  are welded or bonded together. 
       FIG. 46  illustrates yet another embodiment, in which the cutting belt  5605  is made from a deep drawn can  5600 . A right cylinder is formed by deep drawing stainless steel or other suitable material. The can  5600  is open on one end  5601  and closed on the other  5603 . The closed end of the can is removed along out line  5602  forming a continuous belt  5604  into which the patterns described above can be chemically etched, machined or stamped. For example, perpendicular ridges  5607  are chemically etched, stamped or machined into the outer surface of the cutting belt  5605 . For traction with the drive roller a ridge pattern may be formed into the inner surface of the belt. A perpendicular ridge pattern  5606  on the inner surface is shown in  FIG. 46 . It should be noted that the outer and inner surface patterns described above can be used in any combination and that holes through the belt as previously described can be added. 
       FIG. 20  illustrates an alternate embodiment belt cutter in which the frame and tensioning mechanism uses a hinged frame. In this embodiment, the anterior tensioning frame  2001  having support face  205  and hole  204 , and the posterior tensioning frame  2002  are initially pinned together with one pin  2007  to form a hinge. Pin  2007  is slidably received through first hole  2010  then press fit through hole  2014  then slidably received in second hole  2010 . The tensioning frame  2001  and  2002  support drive roller  2003  that is press fit or attached to drive shaft  2006  received within a drive roller  2003 , and an idler roller  2004  rotating on a shaft  2005 . Idler roller  2004  is placed between tabs  2021  protruding from posterior tensioning frame  2002 . Shaft  2005  is slidably received through first hole  2020  and press fit through hole  2018  in idler roller  2004  then slidably received in second hole  2020 . Drive roller  2003  is placed between tabs  2022 . Drive shaft  2006  is slidably received through first hole  2019  and press fit through hole  2017  in drive roller  2003  then slidably received in second hole  2019 . The tensioning frame is angled about the pivot pin  2007  to allow placing the tensioning frame into the cutting belt  2000 . Once in place, the tensioning frame is opened into a straight position aligning the anterior and posterior tensioning frames,  2001  and  2002 , respectively. The tensioning frame is held in this position by placing locking pin  2012  into a receiving hole  2013  in the posterior tensioning frame  2002  that is now aligned with a receiving hole  2011  in the anterior tensioning frame  2001 . Pin  2012  is slidably received through first hole  2013  then press fit through hole  2011  the slidably received in second hole  2013 . The assembled tensioning frame includes a distal tissue protector  2009 , and a cutting belt which is supported in a housing base  2008  having a support face  2016 . Support faces  2016  of housing base  2008  are structured to snap fit on to tension frame assembly at adjoining support faces  2015  on anterior tensioning frame  2001 . 
       FIG. 28  illustrates another embodiment in which the belt cutter  2801 , having frame  2800 , drive shaft  2803 , and shaft  2804 , has the cutting teeth  2802  directed posteriorly, so as to force the femur posteriorly while cutting. 
       FIG. 29  illustrates how the tibial plateau can be prepared by resecting the articular surfaces leaving lateral support surface  2902  and medial support surface  2903  on which tissue guided femoral cutters are placed to prepare the adjacent femoral condyles. The medial  2903  and lateral  2902  support surfaces may be prepared at the same time thereby allowing simultaneous preparation of medial and lateral femoral condyles. Optionally, either medial  2903  or lateral  2902  support surface may be prepared initially followed by preparation of the adjacent femoral condyle. A spacer may be placed in the prepared tibiofemoral compartment followed by preparation of the adjacent tibial support surface followed by preparation of the adjacent femoral condyle. The medial and lateral tibial articular surfaces may be resected independently as shown in  FIG. 29  in which case the tibial eminence  2907  is preserved. Alternatively, the anterior portion of the tibial eminence  2907  may be resected to allow for a bridge or connection between the medial and lateral tibial implants, or the tibial eminence  2907  may be resected. The medial and lateral tibial resections may be co-planar. Alternatively, the medial and lateral resection may be parallel, but not co-planar. In yet another embodiment the medial and lateral tibial resection may not be co-planar nor parallel. The femoral condyles may be resected independently, simultaneously, or in combination with the femoral trochlea. In one embodiment the femoral cutters telescope to distract the joint; either one or both of the tibiofemoral compartments and/or the patellofemoral compartment. Such distraction can be performed under constant load. Alternatively, such distraction may be at discrete displacement steps or distracted to a desirable displacement for condyle(s) and/or trochlea resection. Femoral condyle preparation is guided by the kinematics of the knee joint. The tibia  2901  moves in a predetermined fashion about the femur  2900 . This motion is determined by the soft tissue structures spanning the knee. The anterior cruciate ligament (ACL)  2905  and the posterior cruciate ligament (PCL)  2907  extend from the femoral intracondylar notch to the tibial eminence  2908 . The medial collateral ligament (MCL)  2906  extends from the medial side of the femur to the medial side of the tibia. The lateral collateral ligament (LCL)  2904  extends from the lateral side of the femur to the lateral side of the tibia. The ACL  2905 , PCL  2907 , MCL  2906  and LCL  2904  are the primary ligamentous structures guiding motion of the tibia relative to the femur. 
     In tissue guided surgery a femoral cutter may be placed in each tibiofemoral compartment and in the patellofemoral compartment. The cutting elements are held against the femur while the knee is flexed and extended in order to remove bone from the femur to prepare support surfaces for trochlear and/or condylar implants. Initially, it is beneficial to tension the ligaments spanning the knee and the joint capsule to stabilize the joint with the cutters in place and to provide uniform kinematic motion. As bone is removed it is beneficial to expand the cutters to maintain tension on the ligaments spanning the knee and the joint capsule. The cutters may be expanded incrementally to discrete heights, or variably under constant distraction force. In the first case, which is referred to as “displacement control,” spacers may be placed under the cutters to expand the cutter, or a hydraulic cylinder with incremental fluid filling may be designed into the cutter to expand the cutter, in the patellofemoral compartment or in either of the tibiofemoral compartments. In the second case, which is referred to as “load control,” a hydraulic cylinder, or a bladder, with pressure controlled fluid filling may be designed into the cutter to expand the cutter in the patellofemoral compartment or in the either of the tibiofemoral compartments. 
       FIGS. 30 ,  31  and  32  illustrate that the medial and lateral femoral condyles may be prepared independently with a femoral cutter  3002 , placed in the lateral tibiofemoral compartment first to prepare the lateral femoral condyle. A spacer is placed in the lateral tibiofemoral compartment (not shown) after preparation of the lateral condyle, and the procedure is repeated by placing a femoral cutter  3102  in the medial tibiofemoral compartment. A bladder  3003  or  3103  may be used in conjunction with the lateral or medial femoral cutter, respectively. 
       FIG. 32  illustrates that the femoral trochlea may be prepared by placing a femoral cutter  3202  on the patella. The cutter can be structured to prepare a linear surface generally in a medial—lateral orientation and curved in a sagittal plane. Alternately, cutting elements  3206  as shown in inset of  FIG. 32 , the cutter, structured with various cutting elements to include barrel cutters, belt cutters, reciprocating cutters or shavers, may be contoured to simulate the shape of the patellar groove. Telescoping bellows  3203  may be used as well. 
       FIGS. 34 and 35  illustrate two barrel cutters linked together. In preparing the medial and lateral tibiofemoral compartments it may be beneficial to place femoral cutters in each compartment and simultaneously prepare the medial and lateral femoral condyles. In the case of the barrel cutters, the two cutters are linked together with one cutter  3402 , having telescoping platform  3406 , placed in the lateral tibiofemoral compartment and the other cutter  3403 , having telescoping platform  3405 , placed in the medial tibiofemoral compartment. The connecting bridge  3404  transfers torque from drive shaft  3407  between the two femoral cutters. Alternately, the two cutters may be powered independently. The connecting bridge  3404  may be rigid and of fixed length or in another embodiment the connecting bridge  3404  is flexible and telescopes to enable independent positioning of the femoral cutters within each tibiofemoral compartment. 
       FIGS. 36 and 37  illustrate two reciprocating cutters linked together, with one cutter  3602  placed in the lateral tibiofemoral compartment and the other cutter  3603  placed in the medial tibiofemoral compartment. The connecting bridge  3604  transfers torque from drive shaft  3605  between the two femoral cutters. Alternately, the two cutters may be powered independently. The connecting bridge  3604  may be rigid and of fixed length or in a preferred embodiment the connecting bridge  3604  is flexible and telescopes to enable independent positioning of the femoral cutters within each tibiofemoral compartment. 
       FIGS. 27 ,  38  and  39  illustrate two belt cutters linked together, to form a dual belt cutter  2707 , with one cutter  2702  or  3802  placed in the lateral tibiofemoral compartment (between femurs  2700  or  3600  and tibias  2701  or  3601 ) and the other cutter  2706  or  3803  placed in the medial tibiofemoral compartment. The connecting bridge  2703  or  3804  transfers torque between the two femoral cutters. Alternately, the two cutters may be powered independently. The connecting bridge  2703  or  3804  may be rigid and of fixed length or in a preferred embodiment the connecting bridge  2703  or  3804  is flexible and telescopes to enable independent positioning of the femoral cutters within each tibiofemoral compartment. A telescoping bladder  2705  may be placed under each belt cutter. 
       FIG. 23  illustrates a bladder, shown in a collapsed form. As described above, it is desirable to extend a femoral cutter once it has been placed in either of the tibiofemoral compartments or in the patellofemoral compartment. In one embodiment a fluid or gas filled bladder is placed under the femoral cutter to extend the bladder—cutter combination within the joint space. A bladder  2300  as shown in  FIG. 23  can be made of a suitable material, such as, but not limited to. PET, nylon, polyethylene or urethane. In its collapsed form the bladder  2300  is flat and can be filled via a port  2302  and neck  2301  in one end. Alternately, there may be two ports (not shown) to allow air to bleed from the bladder as fluid is injected into the bladder. The bladder may be compliant to enable expansion in all directions once placed between a femoral cutter and the tibia, or between a femoral cutter and patella. Alternatively, the bladder may be non-compliant to constrain bladder expansion to a designed volume. 
     In preparing the femoral articular surfaces the femoral cutters may require greater translational stability than what is provided by a free standing bladder. Such stability can be provided by designing a telescoping device within the cutter as described herein, then placing the bladder within this telescoping section. In addition, the bladder may be susceptible to puncture by instruments used in the surgical procedure or by the bony support surface. Hence, it may be desirable to house the bladder in an expandable platform that can be placed between the femoral cutter and the tibia or the patella. 
       FIGS. 24 ,  25  and  26  illustrate an expandable housing which may have an expandable bladder housed within. The expandable housing may be fabricated out of metal, plastic or other suitable material. The top plate  2400  and bottom plate  2401  can be rigid or semi-rigid. The sidewalls  2402  and  2403  can fold either in on one another or out on one another to minimize thickness in a collapsed state (see  FIG. 25 ). An opening  2404  is provided for the neck  2301  of the bladder. 
       FIG. 26  illustrates the housing as the bladder within is filled such that the expandable housing telescopes to a designed height. If filled with sterile saline or other suitable fluid that is incompressible the height of the expandable housing can be incrementally increased or decreased to facilitate appropriate femoral resection. Alternatively, the fluid can be introduced into the bladder  2300  within the expandable housing under pressure control in which case the distraction force within the tibiofemoral or patellofemoral compartment can be controlled to facilitate appropriate femoral resection. 
       FIGS. 47 and 48  illustrate a shaver being placed in a tibiofemoral joint and the knee flexed and extended to move the femoral condyle over the cutting elements of the shaver to remove material from the condyle. In another embodiment a reciprocating motion is applied to the shaver to enhance material removal from the condyle while the knee is flexed and extended. As shown in  FIGS. 47 and 48 , a femoral shaver designed for use in either the medial or lateral tibiofemoral compartments provides a frame  5805  with a flat support surface for support on the prepared tibial plateau. The femoral condyle is sculpted by a not of cutting elements  5810  integral to a cartridge  5800 . Alternately, the cutting elements  5810  may be designed as an insert that fits into the cartridge  5800 . A rigid or flexible drive shaft extension (not shown) can be attached between the drive shaft  5802  and a rotational power supply such as a surgical power drill or a motor. 
     A reciprocating motion can be applied to the cartridge  5800  to enhance material removal from the femoral condyle. The cartridge shown is designed to move axially in a channel  5813  within the frame  5805 . In one embodiment a drive cam  5803  converts rotational input to the drive shaft  5802  via an off-set cam  5804  spinning in a transverse slot  5814  in the cartridge  5800 . The drive cam  5803  is supported in a bearing  5808  placed in a countersunk hole  5812  in the frame  5805  and held in place with a washer  5806  and a retainer  5807 . 
     As material is removed from the femoral condyle it is desirable to increase the height of the shaver accordingly that is to extend the shaver within the tibiofemoral compartment. The cartridge  5800  is free to move vertically in the frame  5805 . One or more shims  5801 , each having two arms  5811  designed to pass along side the drive cam  5803 , can be placed between the cartridge  5800  and frame  5805  to extend the shaver. 
       FIGS. 49 ,  50 ,  51  and  57  illustrate an instrument, the bone scribe assembly  4  as shown in  FIG. 50 , to prepare or scribe a guide line in the articular surface of the distal femur. Turning to  FIG. 49 , such instrument including a bone scribing insert  1 , serial distractor  2  and tibial trial base  3 . The area of contact between the bony surfaces of the tibiofemoral and patellofemoral compartments move along the surface of the femur, within each compartment, as the knee flexes and extends. After one or both of the tibial plateaus has been resected, the knee is placed in flexion and a tibial trial base  3  and a bone scribe assembly  4  are placed on resected bone surface positioning rasp  5  appropriately along the respective femoral condyle. As the knee is extended, rasp  5  scribes a shallow groove into the femoral condyle indicating the path to be followed by a primary sculpting instrument described below. As illustrated in  FIG. 51 , the bone scribe assembly  4  scribes a guide line  6  in the surface of the medial femoral condyle  7  to provide the surgeon an indication of guide surface location and implant location before committing to preparing the guide surface, analogous to the adage “measure twice and cut once.” Exposure to the surgical site attained by tissue retractors  8  and  9 . In similar fashion, a bone scribe assembly (not shown) may be structured for support by a resected patella to prepare a guide line in the femoral trochlea before use of a primary sculpting instrument to prepare a guide surface in the trochlea as described later in this specification. 
     The bone scribe insert  1  includes a rasp  5 , scribe body  10  and scribe cap  11  as shown in  FIGS. 49 ,  50  and  57 . The rasp  5  is slidably received and secured in hole  12 . At least one surface of the rasp  5  is serrated  13  to provide a cutting surface to remove cartilage and bone when slid along the surface of an adjacent bone. Scribe body  10  is slidably received in channel  14  of adaptor  49  which is releasably fixed in receiving chamber  48  of serial distractor  2  and secured in place by scribe cap  11  by internal threads  15  engaging with external threads  17  on serial distractor  2 . Rasp  5  is longitudinally supported in groove  29  in support face  28 . As shown in  FIGS. 50 ,  51  and  58  the bone scribe assembly  4  is placed on the resected tibial plateau between the tibial resection and femoral condyle. The distraction platform  34  is held in a collapsed position when handle  26  is in a forward position, which is towards the patient, thereby moving pin  36  up incline  44  to compress springs  39  and retract cylinders  40  into housing  27 . The forward aspect of incline  44  is structured with a flat  45  to lock the distraction platform  34  in a collapsed position. With the bone scribe assembly  4  in position, handle  24  is moved backward releasing distraction platform  34  forcing the rasp  5  against the femoral condyle. Starting with the knee in flexion, the knee is extended sliding the rasp  5  along the surface of the femoral condyle  7  to prepare a shallow groove  6  in the condyle. Groove  6  providing an indication to the surgeon of proper positioning of the serial distractor  2  for subsequent sculpting of the condyle  7 . 
     Referring to  FIG. 58 , springs  39  provide distraction force in the range of 2 to 20 pounds. Springs  39  are contained in cylinders  40 . Bosses  35  extending from distraction platform  34  pass through clearance holes (not shown) in cylinders  40 . Retaining rings  38  secure to bosses  35  to fix distraction platform  34  to cylinders  40 . Pins  36  retain cylinders  40  by engaging openings  43  in ramp bar  24 . 
     The scribe insert  1  is removed from the serial distractor  2  by unthreading scribe cap  11  from adapter  49  leaving the serial distractor  2  within the tibiofemoral joint space. Referring to  FIGS. 52 and 55 , the motor sculpting element assembly  6162  is slidably received in adapter  49 . The knee is placed in flexion. With the motor running, the forward end  6163  of the sculpting element  50  is advanced into the femoral condyle  7  with the motor sculpting element assembly  6162  releasably fixed to serial distractor  2 . As assembled, serial distractor  2  and motor sculpting assembly  162  form one embodiment of the primary sculpting instrument. The primary sculpting instrument is supported by the tibial trial base which in turn is supported by the resected tibial plateau. Alternatively, the primary sculpting instrument is supported directly on the resected tibial plateau. The knee is extended to machine an initial guide surface  41  in the femoral condyle  7  as illustrated in  FIG. 55 . Such guide surface being of uniform depth from the articular surface of the condyle  7 . The motor sculpting element assembly  6162  is released and removed from the serial distractor  2 . The serial distractor  2  is collapsed and removed from the tibiofemoral joint. 
       FIG. 54  illustrates one embodiment of a serial distractor  2  assembled with motor sculpting element assembly  1  and tibial trial base  3  in which the distraction platform  34  is supported by the tibial trial base  3 . One embodiment of the primary sculpting instrument is formed by the assembled serial distractor  2  and motor sculpting element assembly  1 . In this embodiment the primary sculpting instrument distracts the tibiofemoral joint while positioning the sculpting element  50  at a constant depth below the femoral articular surface thereby creating an initial guide surface at a uniform depth below the condyle surface. Such initial surface is deepened and kinematically prepared with another embodiment of the primary sculpting instrument structured with the parallel distractor  164 , shown in  FIGS. 60 and 65 , described below. Alternatively, the secondary sculpting instrument, as described later in the specification, may use the initial guide surface prepared by the primary sculpting instrument structured with the serial distractor  2  to guide preparation of an implant bone support surface in the femoral condyle. 
     Referring to  FIG. 54 , handle  26  is in a backward position releasing the distraction platform  34  to apply distraction force between tibial distraction platform  34  and femoral condyle  7  as shown in  FIG. 55  in contact with support face  28 . Sculpting element  50  is supported releasably secured in collet  55  by clamp nut  53  and drive tube  57 . Drive tube  57  is rotatably supported by bearing  59  contained in hole  60  of barrel  61 . Barrel  61  is secured to motor  73  with threaded fasteners (not shown) in flange  70  and extending from holes  72  of motor  73 . Adaptor  49  is slidably received over barrel  61  of motor sculpting assembly  6162 . Adaptor  49  is then passed into receiving chamber  48  of body  27  of serial distractor  2 . 
     Referring to  FIG. 56 , one embodiment of the motor sculpting element assembly  6162  is assembled by fixing drive tube  57  to drive shaft  71  of motor  73  and attaching flange  70  to threaded holes  72  with threaded fasteners (not shown). Bearing  59  supported in barrel hole  60  supports drive tube  57 . Collet  55  is slidably received in drive tube  57  and locked with clamp nut  53  threaded to drive tube  57 . Collet  54  releasably clamps sculpting element  50  at hex attachment  51 . 
     In one embodiment, tissue guided surgery is provided by distracting the tibiofemoral joint under load control while sculpting the femoral condyle with a sculpting element at a predetermined distance from the resected tibial plateau. Referring to  FIGS. 59 through 64 , parallel distractor  6164  applies a distraction force between the resected tibial plateau and femoral condyle. The distraction platform  77  is held in a collapsed position when handle  74  is in a forward position, which is towards the patient, thereby moving pin  83  down incline  97  to compress springs  81  and retract cylinders  80  into housing  84 . The forward aspect of incline  97  is structured with a flat  99  to lock the distraction platform  77  in a collapsed position. Springs  81  provide distraction force in the range of 2 to 20 pounds. Springs  81  are contained in cylinders  80 . Bosses  98  extending from distraction platform  77  pass through clearance holes  165  in cylinders  80 . Retaining rings  82  secure to bosses  98  to fix distraction platform  77  to cylinders  80 . Pins  83  retain cylinders  80  by engaging openings  96  in ramp bar  94 . 
     The parallel distractor  6164  is locked in a collapsed position. With the knee in flexion, tibial trial base  3  and parallel distractor  6164  are placed on the resected tibial plateau. Alternatively, parallel distractor  6162  is placed directly on resected tibial plateau. The parallel distractor  6164  is unlocked by rotating handle  74  backward, away from the patient, to apply distraction force between the tibia and femur. Barrel  61  of motor sculpting assembly  162  is slidably received in channel  14  of adaptor  49  and is releasably fixed therein. The motor sculpting element assembly  6162  is aligned with the initial guide surface previously prepared in the femoral condyle and the sculpting element  50  is advanced into the femoral condyle. Adaptor  49  is slidably received in receiving chamber  6172  of body  84  and is releasably fixed therein. The assembled parallel distractor  6164  and motor sculpting element assembly  6162  is another embodiment of the primary sculpting instrument of the current invention. The knee is extended. The parallel distractor  6164  maintains tibiofemoral distraction force, thereby providing load control of distraction, during knee extension while supporting the sculpting element  50  at a predetermined distance from the resected tibial plateau. With a dynamic distraction force applied between the tibia and femur, knee kinematics as determined by the anterior and posterior cruciate ligaments, the medial and lateral collateral ligaments and soft tissue structures spanning the knee, guide the separation between the tibia and femur throughout range of motion. The sculpting element  50  at a fixed distance from the resected tibial plateau prepares a guide surface according to the patient&#39;s knee kinematics. 
     Referring to  FIGS. 61 through 65 , the primary sculpting instrument embodiment formed by the assembly of parallel distractor  6164  and motor sculpting assembly  6162  is structured for collapsing the parallel distractor  6164  by rotating handle  74  forward, as illustrated in  FIGS. 61 and 62 , to slide ramp bar  94  backward thereby sliding pin  83  along ramp  97  in hole  6168  to urge distraction platform  77  towards body  84  and compress springs  81 . Lock  99 , as shown in  FIG. 63 , at the end of ramp  97  locks pin  83  with the distraction platform  77  in a collapsed position. 
     Referring to  FIGS. 63 and 64 , handle  74  moved backwards unlocks pin  83  from lock  99  allowing distraction platform  77  to apply load to femoral condyle, such load reacted between the bottom of body  84  and tibial trial base  3  supported on resected tibial plateau. Alternatively, body  84  may be supported directly on resected tibial plateau. 
     The secondary sculpting instrument references the guide surface to prepare an implant support surface in the femoral condyle at a predetermined distance from the guide surface as described below. The distraction platform  77  may be planar. Alternatively, as shown in  FIG. 66 , the distraction platform  6101  may be contoured as a cylinder to guide the femoral condyle centrally on the sculpting element (not shown). Alternatively, the distraction platform may be concave or dished to further capture the femoral condyle to guide the femoral condyle in a generally central location over the sculpting element. 
       FIGS. 67 ,  68  and  69  illustrate one embodiment of the secondary sculpting instrument  6102  in which cutting elements  6107  and  6108  are supported by base  6120  and cover  6104 . One or more cutting elements  6107  or  6108  are driven by spline gears  6113  supported between flanges  6124  in slots  6125 . Torque is applied by a motor (not shown) releasably connected to adaptor  6109  by threaded interface  6106  and to driveshaft  6105 . Driveshaft  6105  is assembled to bevel gear  6110  which meshes with bevel gear  6112  to transfer torque via shaft  6116  to spline gear  6115 . Bushings  6114  provide wear resistance at shaft  6117  and  6116  base  6120  and cover  6104  interfaces. The drive train formed by spline gears  6113  rotate adjacent cutting elements  6107  and  6108  in opposite directions. Alternatively, idler spline gears (not shown) may be used between spline gears  6113  to rotate adjacent cutting elements  6107  and  6108  in the same direction. Cover  6104  is structured to form guide element  6103  which is structured to capture spline gears  6113  and cutting elements  6107  and  6108  between flanges  6124  within slots  6125 . 
     Another embodiment of the secondary sculpting instrument is illustrated in  FIGS. 70 ,  71  and  72  in which cutting elements  6130  and  6131  are supported by base  6139  and cover  6128 . One or more cutting elements  6130  or  6131  are driven by connecting bars  6134  and  6135  supported between flanges  6152  in slots  6170 . Torque is applied by a motor (not shown) releasably connected to adaptor  6136  by threaded interface  6173  and to driveshaft  6137 . Driveshaft  6137  is assembled to bevel gear  6142  which meshes with bevel gear  6144  to transfer torque via shaft  6146  to spline gear  6143 . Spline gear  6143  meshes with spline gear  6154  which assembles with crankshaft  6147 . Crankshaft  6147  is structured with two cams  6149  and  6150 . Cam  6149  is slidably received in hole  6169  in first connecting bar  6134 . Can  6150  is slidably received in second connecting bar  6135 . Rotation of crankshaft  6147  drives connecting bars  6134  and  6135  to transfer torque to one or more cutting elements  6130  or  6131  through crank  6132 . Crank  6132  is structured with two cams  6159  and  6160  orientated to synchronize with crankshaft  6147  cams  6149  and  6150 , respectively. Crank  6132  is structured with bosses  6133  that are slidably received by cutting elements  6130  and  6131  to transfer torque to cutting elements  6130  and  6131 . Bushings  6145  and  6148  provide wear resistance at shaft  6146  and crankshaft  6147  to base  6120  and cover  6104  interfaces. The drive train formed by two connecting arms  6134  and  6135  rotate two or more cutting elements  6130  and  6131  in the same direction. Cover  6128  is structured to form guide element  6129  which is structured to capture connecting arms  6134  and  6135  and cutting elements  6130  and  6131  between flanges  6152  within slots  6170 . 
       FIG. 73  illustrates the secondary sculpting instrument supported on a resected tibial plateau of tibia  6128  with guide element  6129  slidably received in guide surface  41  previously prepared by primary sculpting instrument described above. Secondary sculpting instrument preparing implant bone support surface  6155  by flexing and extending the knee. Alternatively, the secondary sculpting instrument may be structured to include or work with each embodiment of distraction apparatus described herein. Numerous embodiments of the primary sculpting instrument may be structured by incorporating each embodiment of distraction apparatus described herein. Numerous embodiments of the primary and secondary sculpting instruments may be structured by incorporating combinations of each of the sculpting elements or cutter elements and drive mechanisms described herein. 
     The description above is provided in order to illustrate various examples and embodiments of the invention and is not an exhaustive list of all combinations and variations of the present invention. It should be understood that various changes, adaptations and modifications may be made therein without departing from the spirit of the invention and the scope of the appended claims. The scope of the invention is provided in the claims which follow.