Patent Abstract:
A system and method for placing an implant into or onto supporting bone, or between adjacent bones, without impaction is disclosed. The system includes an implant, a distracter, and a sleeve. Optionally, the invention includes an alignment guide, a surgical navigational tracker, and a bone displacer. The sleeve is structured to interpose the implant and supporting bone and provide a differential engagement force between the sleeve-implant interface and the sleeve-bone interface to preferentially move the implant into, onto or between supporting bone structures.

Full Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on and claims the benefit of U.S. Provisional Application No. 60/703,120, filed Jul. 28, 2005, the entirety of which is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    This invention relates to implants and instruments for use in orthopaedic surgery. More particularly, this invention relates to a device and method for aligning, orienting and placing an implant into or onto supporting bone, or between adjacent bones without impaction. 
         [0004]    2. Description of the Related Art 
         [0005]    The field of orthopaedic surgery includes joint arthroplasty, spinal disc replacement, spinal interbody fusion, vertebral compression fracture reduction and realignment osteotomies. Joint arthroplasty includes partial and total replacement of the bony support surfaces of articulating joints, to include knee, hip, shoulder, spinal facet, ankle, toe, finger, wrist and elbow. Spinal disc replacement includes partial and total replacement of the bony support surfaces of vertebral bodies, which are the endplates, and the annulus, the nucleus and combinations thereof. Within the specification reference is made to a spinal motion segment which is the combination of structures providing motion between adjacent vertebral bodies, that is two facet joints and a spinal disc. For the purposes of this specification, the term “Kinematic Restoration” will be used to broadly refer to joint arthroplasty, as defined above, and spinal disc replacement, as defined above, in human and in veterinarian applications. 
         [0006]    In a healthy articulating joint, a smooth and resilient surface consisting of articular cartilage covers the bony structures to provide bone support surfaces. In a healthy spinal disc, vertebral body endplates provide bone support surfaces for the interposed annulus and nucleus. The annulus is attached to adjoining vertebral body endplates. Articulating joints and spinal discs generally consist of two or more relatively rigid bone structures that maintain a kinematic and dynamic relationship one to the other. Soft tissue structures spanning or interposed between the bone structures hold the bone structures together and aid in defining the motion or kinematics of one bone structure to the other. 
         [0007]    The bone support surfaces, as described for articulating joints and for spinal discs, work in combination with the soft tissue structures spanning or interposed between them to form a mechanism that defines the envelop of motion of adjacent bone structures one to the other. Within a typical envelop of motion, the bone 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. Arthritis, degeneration, trauma and other pathologies lead to pain, deformity and compromised motion in articulating joints and in spinal discs. 
         [0008]    Orthopaedic surgery includes Kinematic Restoration procedures as described above which relieve pain, correct deformity and restore motion in pathologic articulating joints and spinal discs. It is typical in such procedures to impact one or more implants into or onto the bone support surfaces or between adjacent bone support surfaces. One or more of the related bone support surfaces are prepared to receive one or more implants, such implants being placed and forcibly impacted therein, thereon or there between such bone support surfaces. 
         [0009]    Spinal interbody fusion involves removal of a pathological nucleus, preparing the endplates to form bone support surfaces and includes placement of one or more implants, either of synthetic material, allograft bone, autograft bone or a combination thereof, between adjacent vertebral bodies to facilitate fusion between the vertebral bodies. Vertebral compression fracture reduction involves creating a cavity in the vertebral body to form bone support surfaces and includes placement of one or more implants, either of            
         [0010]    Suitable synthetic materials for the implants described above include cobalt chromium alloys, titanium and titanium alloys, stainless steel, zirconia, alumina and other ceramic materials, polyethylene, urethanes, PEEK, carbon fiber filled PEEK, calcium based composites, Nitinol, and polymethylmethacrylate. 
         [0011]    Orthopaedic implants for Kinematic Restoration can be secured to bone with cement or grouting material, by bone ingrowth or ongrowth, or by biologic materials. In the case of ingrowth or ongrowth, or biologic fixation, a close and stable fit between implant and supporting bone is required to promote positive bone remodeling. Such a fit has traditionally been attained by press-fitting the implant into, onto or between supporting bone. In the case of placing an implant into supporting bone for bone ingrowth or ongrowth, for example an acetabular cup in total hip replacement, the acetabulum is prepared and a corresponding cup size is selected to provide a line to line fit or a press-fit between the cup and the prepared acetabulum. Alternatively, if an implant is to be fitted over a supporting bone for bone ingrowth or ongrowth, for example the femoral component of a total knee replacement, the distal femur is prepared and a corresponding femoral component size is selected to provide a line to line fit or a press-fit between the femoral component and the prepared femur. The implant is held in position by an impaction device and impacted into place with a mallet. Such impaction is traumatic. Alternatively, if an implant is to be fitted between adjacent bones for bone ingrowth or ongrowth, for example a spinal disc replacement, the involved endplates are prepared and a corresponding disc replacement size is selected to provide proper height and tension of the interbody space. The implant may be held in position by an impaction device and impacted into place with a mallet. Such impaction is traumatic. Alternatively, the interbody space may be overly distracted to place the implant. Such over distraction is traumatic. 
         [0012]    In surgical procedures relying on surgical navigation to aid the surgeon in restoring alignment and in aligning and positioning implants, such impaction may loosen and move navigational trackers introducing error in the surgical navigation of the procedure. In addition, subsequent impactions may alter alignment of the implant relative to supporting bone. Implant alignment is critical for long term function and durability of the implant. 
         [0013]    Similarly, in spinal interbody fusion, vertebral compression fracture reduction and realignment osteotomy procedures a close and stable fit between implant and supporting bone is required to promote positive bone remodeling. Such a fit has traditionally been attained by press-fitting the implant between adjacent bones or into a supporting bone. The implant is held in position by an impaction device and impacted into place with a mallet. Such impaction is traumatic. Alternatively, the receiving site, either between adjacent bones for spinal interbody fusion, or within a bone for vertebral compression fracture reduction or realignment osteotomies, requires over distraction of the receiving site to place the implant. Such over distraction is traumatic. 
         [0014]    There exists a need for a device and method to accurately align and orient an implant with the supporting bone. There also exists a need for a device and method to place an implant into, onto or between supporting bone without impaction or over distraction. 
       BRIEF SUMMARY OF THE INVENTION 
       [0015]    The present invention provides a system and method for implant placement into or onto a supporting bone, or between adjacent bones, which involves less or minimally invasive surgical procedures. The present invention further provides a system and method to accurately align and orient an implant. Optionally, the present invention further provides an apparatus and method to displace adjacent bones while placing an implant onto or into one or more of the bones, or between the bones. The present invention provides an apparatus for placing an implant within a prepared bone cavity, over a prepared bone surface, or between prepared surfaces of adjacent bones wherein the implant is structured to press-fit into, onto or between the supporting bone or bones to provide initial implant stability, anatomical alignment and appropriate relative position of the supporting bone or bones. The implant having a final seated position relative to supporting bone or bones, when in such position the implant is placed properly in supporting bone or bones and the supporting bone restricts further advancement of the implant. As used herein, the following terms have the following definitions: 
         [0016]    Orienting—For the purposes of the present invention orientating pertains to 1) orientating sub-components of an implant to one another, and 2) orientating implant components of a Kinematic Restoration to one another. In both cases orientating means to bring the parts into working relationship to one another so that the assembly of parts functions as intended. 
         [0017]    Aligning—For the purposes of the present invention aligning pertains to 1) alignment of sub-components of an implant to supporting bone, such supporting bone being properly aligned, and 2) alignment of implant components of a Kinematic Restoration to supporting bone. In both cases aligning means to bring the parts into correct relative position with respect to the supporting bone so that the arthroplasty functions as intended. 
         [0018]    Implant component and sub-component—For the purposes of the present invention an implant component refers to the parts that make up the arthroplasty, for example femoral, tibial and patellar components make up a total knee arthroplasty. Sub-component refers to the parts that make up the implant component. Each component may be unitary in construction, or may include a plurality of sub-components. Reference made to an “implant” refers to one or more of the components, or one or more of the sub-components, or a combination thereof. 
         [0019]    Engagement force—For purposes of the present invention, the term “engagement force” as it relates to the sleeve to implant interface and to the sleeve to bone interface shall be defined as the force tending to slide a surface along another at which relative motion between the surfaces starts. Such engagement force may be provided by a number of mating surface structures to include frictional interference, ridges, grit blast, chemically etched, corrugated or patterned between the surfaces wherein the magnitude of the engagement force may be established by providing an appropriate coefficient of friction between the adjacent surfaces; engagement between adjoining surfaces, such engagement being mechanical interlock, releasable mechanical interlocks, pined interface, releasable pined interface, bonding of the interface, or other suitable means to restrain relative movement between two or more parts. Wherein the restraint has a threshold that when reached the parts move relative to one another, that threshold being the engagement force. The sleeve to implant interface and the sleeve to bone interface are under compression because the sleeve in the present invention is interposed between the implant and supporting bone and the implant is structured to provide a press-fit with supporting bone. 
         [0020]    Joint Arthroplasty—For the purposes of this specification, the term “joint arthroplasty” includes partial and total replacement of the bony support surfaces of articulating joints, to include knee, hip, shoulder, spinal facet, ankle, toe, finger, wrist and elbow. 
         [0021]    Spinal Disc Replacement—For the purposes of this specification, the term “spinal disc replacement” includes partial and total replacement of the bony support surfaces of vertebral bodies, which are the endplates, and the annulus, the nucleus and combinations thereof. 
         [0022]    Spinal Motion Segment—For the purposes of this specification, the term “spinal motion segment” is the combination of structures providing motion between adjacent vertebral bodies, that is two facet joints and a spinal disc. 
         [0023]    Kinematic Restoration—For the purposes of this specification, the term “kinematic restoration” will be used to broadly refer to joint arthroplasty, as defined herein, and spinal disc replacement, as defined above, in human and in veterinarian applications. 
         [0024]    The present invention is comprised of an implant, a distracter, and a sleeve. The distracter is structured to provide a gradual insertion force to move the implant into, onto or between supporting bone or bones with the insertion force reacted by the supporting bone or bones. The sleeve is structured to interpose the implant and supporting bone and provide a differential engagement force between the sleeve-implant interface and the sleeve-bone interface to preferentially move the implant into, onto or between supporting bone structures. Optionally, the present invention may include an alignment guide. Alternatively, the present invention may include a surgical navigational tracker. The alignment guide is structured to orient and align the implant. Alternatively, the navigational tracker is structured to orient and align the implant. Optionally, the present invention may include a bone displacer structured to distract adjacent bones or adjacent bone support surfaces to facilitate placement of an implant. 
         [0025]    The implant structured for use in Kinematic Restoration, spinal interbody fusion, vertebral compression fracture reduction or realignment osteotomy 
         [0026]    The sleeve structured to:
       interpose implant and bone or bones,   to be of unitary construction,   alternatively, to be a plurality of sleeves,   to have a first surface structured to engage an implant (i.e. implant engagement),   to have a second surface structured to engage a bone or bones (i.e. bone engagement).       
 
         [0032]    The distracter structured to:
       connect to an implant (i.e. implant connection),   alternatively, connect to bone or bones (i.e. bone connection),   connect to a sleeve or plurality of sleeves (i.e. sleeve connection),   displace the implant relative to the sleeve,   displace the sleeve relative to the bone or bones,   displace the implant relative to the bone or bones.       
 
         [0039]    In one embodiment of the present invention the distracter and sleeve are structured to place an implant between adjacent first and second bones, wherein:
       the distracter is connected to the implant and to the sleeve,   the sleeve has a first surface structured to engage the implant and a second surface structured to engage the first and second bones,   the sleeve to bone engagement force being greater than the sleeve to implant engagement force,   the distracter structured to displace the implant towards the implant&#39;s final seated position during which the sleeve to bone engagement force has not been exceeded and the relative position of the sleeve to the first and second bone does not significantly change,   the implant is advanced to it&#39;s final seated position at which point the first and second bone restrict further advancement of the implant,   continued displacement of the distracter then overcomes the sleeve to bone engagement force and the sleeve is moved away from the implant&#39;s final seated position and out of the implant to bone interface,   the sleeve and distracter are then removed and the implant is in proper position.       
 
         [0047]    In an alternative embodiment of the present invention the distracter and sleeve are structured to place an implant into a bone cavity, wherein:
       the distracter is connected to the implant and to the sleeve,   the sleeve has a first surface structured to engage the implant and a second surface structured to engage the bone cavity,   the sleeve to bone engagement force being greater than the sleeve to implant engagement force,   the distracter structured to displace the implant towards the implant&#39;s final seated position during which the sleeve to bone engagement force has not been exceeded and the relative position of the sleeve to bone cavity does not significantly change,   the implant is advanced to it&#39;s final seated position at which point the bone restricts further advancement of the implant,   continued displacement of the distracter then overcomes the sleeve to bone engagement force and the sleeve is moved away from the implant&#39;s final seated position and out of the implant to bone interface,   the sleeve and distracter are then removed and the implant is in proper position.       
 
         [0055]    In yet another embodiment of the present invention the distracter and sleeve are structured to place an implant onto a bone, wherein:
       the distracter is connected to the bone and to the sleeve,   the sleeve has a first surface structured to engage the implant and a second surface structured to engage the bone,   the sleeve to bone engagement force being lower than the sleeve to implant engagement force,   the distracter structured to displace the sleeve towards the implant&#39;s final seated position during which the sleeve to implant engagement force has not been exceeded and the relative position of the sleeve to implant does not significantly change,   the implant is advanced to it&#39;s final seated position at which point the bone restricts further advancement of the implant,   continued displacement of the distracter then overcomes the sleeve to implant engagement force and the sleeve is moved away from the implant&#39;s final seated position and out of the implant to bone interface,   the sleeve and distracter are then removed and the implant is in proper position.       
 
         [0063]    Optionally, each of the embodiments described above may include an alignment guide structured to:
       attach to the inserter,   alternatively, attach to the sleeve,   alternatively, attach to the implant,   alternatively, attach to one or more of the supporting bones,   provide alignment rods aligned with anatomic features or implant features to provide a geometric reference between the implant and one or more of the supporting bones to align and orient the implant.       
 
         [0069]    Optionally, each of the embodiments described above may include a surgical navigational tracker structured to:
       attach to the inserter,   alternatively, attach to the sleeve,   alternatively, attach to the implant,   alternatively, attach to one or more of the supporting bones,   support reflective spheres typically used with optical surgical navigation system. Alternatively, to support electromagnetic targets typically used with electromagnetic surgical navigation systems.   be navigated by the surgical navigation system to aid the surgeon in orienting and aligning the implant and to provide a geometric reference between the implant and one or more of the supporting bones to align and orient the implant.       
 
         [0076]    Optionally, each of the embodiments described above may include a bone displacer structured to:
       attach to the distracter,   alternatively, be integral with the distracter,   attach to one or more of the supporting bones,   attach to the implant,   distract adjacent bones away from one another,   alternatively, distract the distracter away from one or more adjacent bones,   alternatively, distract the implant away from one or more adjacent bones.       
 
         [0084]    The distracter and the bone displacer are structured as hydraulic cylinders each having a piston and cylinder actuated by fluid or air pressure. Alternatively, the distracter or bone displacer may be mechanically actuated by screw mechanisms, scissors mechanisms, lever and fulcrum mechanisms, spring mechanisms, bladders, balloons, bellows, gear mechanisms, rack and pinion mechanisms, and other expandable devices or other elements that provide a force between two or more objects, or combinations thereof. 
         [0085]    The structure of the connections between the distracter and sleeve, distracter and implant, and distracter and bone described above and the structure of the connections between the bone displacer and distracter, bone displacer and bone, and bone displacer and implant, include compressive contact surfaces, threaded interfaces and threaded fasteners, pinned interfaces, “T” slots; dovetail locks; cylindrical interlocks; button interlocks; spherical interlocks; trinkle locks; or a combination of these, or other connecting means used to connect two or more parts. 
         [0086]    Suitable materials for the sleeve as described above and in the detailed description of the invention include cobalt-chromium alloy, stainless steel, titanium, titanium alloys, Nitinol, plastics, including but not limited to urethane, polyethylene and expanded polyethylene, nylon, woven fabric materials, and the like. 
         [0087]    The invention will be further described with reference to the following detailed description taken in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0088]      FIG. 1  is a perspective view of the surgical incision through which the present invention is structured to be used. 
           [0089]      FIG. 2A  is an illustration of a cup placed into a sleeve and placed into a prepared acetabulum in accordance with the present invention. 
           [0090]      FIG. 2B  is a cross sectional detailed view of  FIG. 2A  showing a cup placed into a cup sleeve and placed into a prepared acetabulum in accordance with the present invention. 
           [0091]      FIG. 3  is a cross sectional view showing a cup placed into a cup sleeve and placed into a prepared acetabulum in accordance with the present invention. 
           [0092]      FIG. 4  is a cross sectional view showing a cup placed into a cup sleeve and placed into a prepared acetabulum with a mechanical interlock released in accordance with the present invention. 
           [0093]      FIG. 5  is a perspective view of a sleeve in accordance with the present invention. 
           [0094]      FIG. 6  is a top perspective view of a cup inserter in accordance with the present invention. 
           [0095]      FIG. 7  is bottom perspective view of the cup inserter in accordance with the present invention. 
           [0096]      FIG. 8  is a perspective cross sectional view of the cup inserter of the present invention. 
           [0097]      FIG. 9  is a cross sectional view of the cup inserter of the present invention. 
           [0098]      FIG. 10A  is a side view of a cup inserter aligned for placement of an acetabular cup in accordance with the present invention. 
           [0099]      FIG. 10B  is a side view of a femoral broach in accordance with the present invention. 
           [0100]      FIG. 11  is a side view of a cup inserter inserting an acetabular cup in accordance with the present invention. 
           [0101]      FIG. 12  is a side view of a cup inserter extracting a sleeve in accordance with the present invention. 
           [0102]      FIG. 13   a  is an exploded view of the cup inserter in accordance with the present invention. 
           [0103]      FIG. 13   b  is another exploded view of the cup inserter in accordance with the present invention. 
           [0104]      FIG. 14  is a perspective view of a cup inserter and handle in accordance with the present invention. 
           [0105]      FIG. 15  is a perspective view of a cup inserter, handle and alignment guide in accordance with the present invention. 
           [0106]      FIG. 16  is a perspective view of a cup inserter, handle and surgical navigational tracker in accordance with the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0107]    As described above, the present invention is applicable to orthopaedic surgical procedures for Kinematic Restoration, spinal interbody fusion, vertebral compression fracture reduction and realignment osteotomy. In one embodiment of the present invention, the system is comprised of:
       an implant—in this embodiment the implant is an acetabular cup,   a distracter—in this embodiment the distracter is a cup inserter and specifically the stage II piston and cylinder,   a sleeve—in this embodiment the sleeve is a cup sleeve,   optionally, an alignment guide—in this embodiment the alignment guide is a cup alignment guide,   optionally, a surgical navigational tracker—in this embodiment the surgical navigational tracker is a cup navigational tracker,   optionally, a bone displacer—in this embodiment the bone displacer is the stage I piston and cylinder.       
 
         [0114]    Referring to  FIG. 1 , there is depicted a surgical incision  100  for a less invasive total hip arthroplasty. The muscles and soft tissues spanning the hip joint are exposed and either bluntly dissected along muscle fibers or separated along muscle boundaries. Optionally, select muscles may be taken down to increase surgical exposure and access to the hip joint. Anatomy of interest to this embodiment of the invention includes the pelvis  102 , the acetabulum  104 , the femur  108 , the joint capsule (not shown) and the muscles  105  and ligaments spanning the hip joint. The femoral head is resected at the base of the femoral neck  108  as shown in  FIG. 1  to provide access to the medullary canal to prepare the canal to receive a femoral hip stem. In total hip arthroplasty, the articular surfaces of the proximal femur and the acetabulum are resurfaced. In general, after resecting the femoral head, the femur is prepared by reaming and broaching to prepare the femoral canal to receive a hip stem implant and femoral head implant there on. Alternatively, the femoral head may be sculpted to receive a resurfacing implant structured to fit over the prepared femoral head, this representing another embodiment of the present invention to place an implant onto a prepared bone surface. The acetabulum is generally prepared by reaming a hemispherical cavity to receive an acetabular cup. 
         [0115]    Referring to  FIG. 2A , the cup sleeve  16  interposes the cup  18  and the acetabulum  104 . The cup  18  size is selected to provide a press-fit within the prepared acetabulum  104  and the cup sleeve  16  size is selected to match the cup  18  size. Alternatively, a cup sleeve  16  may be structured to accommodate multiple cup sizes. The cup inserter, described in detail below, provides an insertion force IF to the cup  18  that is reacted by the cup sleeve  16  by a reaction force RF around the distal circumference of the cup sleeve. Now referring to  FIG. 2B , the cup sleeve  16  to acetabulum  104  interface  136  is structured to provide a higher engagement force than the engagement force at the cup sleeve  16  and cup  18  interface  138 . The cup sleeve  16  surface at the sleeve-bone interface  136  is structured with circumferential ridges  17  to provide a mechanical interlock and an engagement force higher than that of the sleeve-implant interface  138  in which the sleeve surface is smooth. The ridges may be machined into the sleeve. Alternatively, the ridges may be chemically milled into the sleeve, or formed into the sleeve by a stamping process. Alternatively, the sleeve surface at the sleeve-bone interface  136  may be structured with a roughened texture as may be created by grit blasting, machining, chemical etching or formed into the sleeve by a stamping process. 
         [0116]    Alternatively, the cup sleeve  16  surface at the sleeve-bone interface  136  may be structured to provide a releasable mechanical interlock. Referring to  FIG. 3 , the cup sleeve  16  may be structured with a circumferential ridge  133  around the proximal edge that engages the acetabulum  104 . A sliding spacer  131  is interposed between the cup sleeve  16  and cup  18  to hold the ridge  133  in an extended position to engage the acetabulum  104 . The sliding spacer  131  is pulled distally by the surgeon grabbing the sliding spacer  131  with a forceps. As shown in  FIG. 4 , when the sliding spacer  131  is pulled from underneath the circumferential ridge  133 , the ridge  133  pulls away from the acetabulum  104  releasing the cup sleeve  16  to slide from the cup  18  and acetabulum  104  interface. Alternatively, the ridge  133  may be intermittent to provide equally spaced tabs around the circumference of the proximal edge of the cup sleeve  16  to engage the acetabulum  104 . 
         [0117]    Now referring to  FIG. 5 , the body of the cup sleeve  16  is formed with a spherical closing  142  of the proximal edge  38 . The longitudinal serrations  36  equally spaced around the cup sleeve  16  provide relief in the cup sleeve  16  as the cup displaces proximally through the cup sleeve  16 . The serrations  36  are positioned relatively close to the proximal edge  38  to provide a lip  44  between each serration  36  and the proximal edge  38 , this lip  44  structured to provide constraint to hold the cup in the cup sleeve while the surgeon handles the cup inserter and cup to place the construct into the surgical site. The lip  44  then fracturing as the cup is advanced into the acetabulum to allow the cup to pass through the cup sleeve  16  as described in greater detail below. The perforations  26  evenly spaced around the distal aspect of the cup sleeve  16  are structured to provide a releasable pinned connection with the cup inserter as described in greater detail below. Alternatively, the perforations  26  may be structured to provide a pinned connection with the cup inserter. 
         [0118]    The body of the cup sleeve  16  may be formed by deep drawing a metal into the shape of the cup sleeve  16 , then truncating the formed can to open the proximal end of the cup sleeve  16  and trimming the distal end  40  of the formed can. Alternatively, the cup sleeve  16  body may be machined. The longitudinal serrations  36  and perforations  26  can be die cut into the cup sleeve  16 . Alternatively, the longitudinal serrations  36  and perforations  26  may be laser cut or die stamped into the cup sleeve. 
         [0119]    Referring now to  FIGS. 6 and 7  which illustrate an assembly of the present invention, the cup  18  is held within the cup sleeve  16 . The cup sleeve  16  is structured to attach to the adapter ring  28  with releasable pinned interlocks that engage perforations  37  in the cup sleeve  16 . In one embodiment, the present invention includes a distracter and a bone displacer. Hydraulic pressure to activate the distracter is provide via a tube  82  which is ported to the stage II piston and cylinder described in detail below. Hydraulic pressure to activate the bone displacer is provided via a tube  80  which is ported to the stage I piston  140  and cylinder described in detail below. The cup inserter  10  is structured to attachably receive a handle to a boss  120  via two bayonet mounting tabs  122 . The manifold cap  46  is structured to be assembled and disassembled with the adapter ring  28  through a threaded connection described below. This threaded connection is locked from loosening during the surgical procedure by a mechanical interlock activated by a manifold lock  48  on the distal surface of the manifold cap  46 . 
         [0120]    The operation of the cup inserter  10  is easiest to describe when referring to  FIGS. 8 and 9  which are cross sectional views of the cup inserter  10  without a cup, but with a cup sleeve  16  illustrated. As described above, first hydraulic pressure supply is used to actuate a distracter structured within the cup inserter  10  and a second hydraulic pressure supply is used to actuate a bone displacer structured within the cup inserter  10 . The distracter is comprised of manifold  20  and stage II piston  24  structured to provide a piston and cylinder mechanism that when pressurized displaces the cup relative to the cup sleeve  16 . Hydraulic pressure is introduced via tube  82  described above and ported to the stage II cylinder  45 . An o-ring  41  provides a pressure seal for the stage II piston  24  and manifold  20 . The manifold  20  engages the adapter ring  28  through a mechanical interlock structured by tabs  60  on the inner diameter of the adapter ring  26  slidingly fitting into receiving pockets  61  in the outside diameter of the manifold  20 . 
         [0121]    The manifold  20  attaches to the cup sleeve  16  via a releasable pinned interlock formed by a cantilever beam  29  and boss  25  in the adaptor ring  28 . Multiple cantilever beam  29  and boss  25  interlocks are equally spaced around the adaptor ring  28  and the number varies with the size of the adaptor ring as structured to attached to various sizes of the cup sleeve  16 . The cantilever beam  29  is deflected inward by applying force to the boss  25  thereby releasing the cup sleeve. The proximal edge of each boss  25  is beveled to allow the cup sleeve to slide over the boss  25  and depress the cantilever beam  29  during assembly of the cup sleeve  16  onto the adaptor ring  28 . Extending from the proximal surface of the stage II piston  20  is a treaded connector  56  structured to attach an adapter post  22 . Adapter posts  22  are provided for each cup size. The proximal end of the adapter post  22  is structured with a treaded connector  22  to attach to the cup. Alternatively, the proximal end of the adapter post  22  may be structured with a boss that slidably fits into a apical hole in the cup. 
         [0122]    Once assembled, the cup inserter  10  is locked in an assembled position by the manifold lock  48  and boss  62  that slidably engages scallops  88  on the distal inner surface of the adapter ring  28 . Releasing the manifold lock  48  allows the manifold  20  to be unthreaded from the manifold cap  46  and disassembly of the cup inserter  10 . 
         [0123]    The bone displacer is comprised of the stage I piston  26  and the cylinder within the manifold  20 . An o-ring  43  provide a pressure seal between the stage I piston  26  and the cylinder within the manifold  20 . The distal end of the stage I piston  26  is structured with a bore  140  to slidably receive the post of a femoral broach to support the cup inserter  10  when in use within the joint cavity. Alternatively, the cup inserter may be used independently without attachment to a broach or support by the femur. 
         [0124]    Turning now to a description of the surgical procedure in which the cup inserter  10  is used to place a cup  18 . The acetabulum  104  and proximal femur have been surgically prepared as described above. The femoral broach that was used to prepare the proximal femur is left in place to support the cup inserter  10 . Starting with  FIG. 10A , the cup inserter  10  and bone displacer are fully retracted. A cup  18  size is selected to provide a press-fit with the prepared acetabulum  104  and assembled with the cup inserter  10  and cup sleeve  16 . The cup handle is assembled to the cup inserter  10  onto boss  120  as described in detail below. Next, the cup inserter  10  is placed onto the broach post  110 , as can be seen in  FIG. 10B , and the hip is reduced to place the cup  18  into the acetabulum  104 . Alternatively, the cup inserter  10  may be attached directly to the femur with screws, pins or other suitable mounting structure. Alternatively, the cup inserter  10  may be supported by the proximal femur without mechanical attachment thereto. Alternatively, the cup inserter  10  may be structured to place the cup without the cup inserter  10  attached to or supported by the femur. 
         [0125]    It should be noted that due to the press-fit interference between the cup  18  and acetabulum  104 , the cup  18  is supported by the distal circumference of the acetabulum leaving a gap  134  apically between the cup  18  and acetabulum  104 . The stage I piston  26  is advanced by applying pressure with a syringe pump until the joint capsule is tensioned appropriately and the cup sleeve  16  engages the acetabulum  104 . The stage II piston  24  is advanced to provide an insertion force to the cup  18 . The insertion force is reacted through the sleeve  16  by a reaction force carried by the adaptor ring  28  attached to the cup sleeve  16 ; hence, the stage II piston  24  is structured to provide a distraction force between the cup  18  and the sleeve  16 . The sleeve  16  is held in place within the acetabulum by the higher engagement force at the sleeve-acetabulum interface, than that of the sleeve-cup interface as previously described. The cup  18  slides relative to the sleeve  116  until the gap apical  134  between the cup  18  and acetabulum  104  is closed. At which point the distraction force provided by the stage II piston  24  pulls the sleeve  16  from the acetabulum  104  by overcoming the frictional force at the sleeve-acetabulum interface as previously described. 
         [0126]    Referring now to  FIG. 11 , as the stage II piston deploys to seat the cup  18 , the stage I piston is adjusted to maintain distraction of the joint capsule and displace the femur. Now referring to  FIG. 12 , after the cup  18  is fully seated in the acetabulum  104 , the stage II piston  24  continues to pull the sleeve  16  from the cup-acetabulum interface until the sleeve  16  is fully removed. At this point the manifold  20  is free from the stage II piston  24  and the sleeve  16 , adaptor ring  28 , manifold  20  and manifold cap  46  assembly are removed from the hip joint cavity by orienting the femur away from the acetabulum and removing these components from the broach post  110 . The stage II piston  24  and adaptor post  22  are then removed from the cup  18 . 
         [0127]    Given the numerous parts making up the cup inserter  10 , it is beneficial to briefly list the parts as shown in exploded views. Referring to  FIGS. 13   a  and  13   b , the cup sleeve  16 , the cup  18 , the adapter post  22 , the stage II piston  24 , the manifold  20  with o-ring  41  assembled, the stage I piston with o-ring  43  assembled, the adapter ring  28 , the manifold gasket  30 , the manifold cap  46 , the manifold lock  48  and the manifold retainer  64 . It is also beneficial to briefly describe the fluid pathways for the distracter, driven by stage II, and the bone displacer, driven by stage I, configurations within the cup inserter  10 . Starting with the pressure supply, a first and a second syringe pump (not shown) are used to provide hydraulic pressure to drive stage I and stage II pistons. Each syringe pump is filled with sterile saline solution. The first syringe pump is connected to stage I via tube  80  and the second syringe pump is connected to stage II via tube  82 . The fluid pathway for stage I is tube  80 -manifold cap  46  port  90 -gasket  30  port  76 -manifold  20  port  84 -leading to manifold  20  internal cylinder  35 . The fluid pathway for stage II is tube  82 -manifold cap  46  port  92 -gasket  30  port  78 -manifold  20  port  86 -leading to manifold  20  external cylinder  27 . 
         [0128]    Referring to  FIG. 14 , in another embodiment in accordance with the present invention, the cup inserter  10  is attached to a handle  126  such that a surgeon places cup inserter  10  and cup  18  directly into the acetabulum and holds sleeve  16  in contact with supporting bone. The handle  126  structured to slidably receive the manifold cap attachment boss  120  with opposing bayonet bosses  122  to engage receiving bayonet openings  124 . The lock nut  130  is structured to secure the bayonet bosses  122  within the receiving bayonet openings  124 , and the clinch nut  132  structured to lock the lock nut  130  in place. Alternatively, the cup inserter  10  may be structured to attach to or be supported by the femur directly or indirectly as described above. The stage II piston  24  is extended to push cup  18  along sleeve  16  and into the acetabulum. The frictional force between sleeve  16  and supporting bone holds sleeve  16  in position relative to the supporting bone until inserter cup  10  is seated in supporting bone. After seating, cup inserter  10  is in proper position and additional pulling force to sleeve  16  slides sleeve  16  from the cup-bone interface. This is continued until sleeve  16  is free of the interface at which time cup inserter  10  and sleeve  16  are removed from the joint cavity and the surgical procedure is completed. 
         [0129]    Optionally, the cup inserter  10  and handle  126  may be structured for attachment of an alignment guide. Referring to  FIG. 15 , an alignment guide  150  with an alignment rod  162  structured to indicate cup inclination and alignment rod  160  structured to indicate cup anteversion relative to the axis of the torso may be used to check alignment of the cup  18  by attaching the alignment guide  150  to handle  126 , such attachment structured as a channel  164  in the upper base  156  and lower base  154  of the alignment guide  150  that slidably fits over the handle  126  via channel  164  and clamps to the handle  126  thumb screw  152  to stabilize the alignment guide  150  in proper alignment relative to the cup inserter  10  and handle  126 . Alternatively, the alignment guide may be attached to the handle  126  by threaded fasteners passed through clearance receiving holes in the upper base  156  and threaded into threaded receiving holes in the handle  126 . 
         [0130]    Optionally, the cup inserter  10  and handle  126  may be structured for attachment of a surgical navigational tracker for use with a surgical navigational system. Referring to  FIG. 16 , a surgical navigational tracker  166  with three reflective spheres  170  supported on a frame  168  and an upper base  156  and lower base  154  of the alignment guide  150  that slidably fits over the handle  126  via channel  164  and clamps to the handle  126  thumb screw  152  to stabilize the alignment guide  150  in proper alignment relative to the cup inserter  10  and handle  126 . Alternatively, the surgical navigational tracker  166  may be attached to the alignment guide  150  to handle  126  by threaded fasteners passed through clearance receiving holes in the upper base  156  and threaded into threaded receiving holes in the handle  126 . Cup  18  alignment is checked with the a surgical navigational tracker  166  attached to the cup inserter  10  and handle  126 . The surgical navigational system will measure cup  18  inclination and anteversion and provide a report to the surgeon. Alternatively, the alignment guide  150  and the surgical navigational tracker  166  may be structured for attachment to the cup inserter  10  and handle  126  with “T” slots; dovetail locks; cylindrical interlocks; button interlocks; spherical interlocks; or a combination of these, or other connecting means used to connect two or more parts. 
         [0131]    While this disclosure covers placing a cup into the acetabulum, the present invention is applicable to orthopaedic surgical procedures for Kinematic Restoration, spinal interbody fusion, vertebral compression fracture reduction and realignment osteotomy. 
         [0132]    It is contemplated that features disclosed in this application can be mixed and matched to suit particular circumstances. Various other modifications and changes will be apparent to those of ordinary skill in the art without departing from the spirit and scope of the present invention. Accordingly, reference should be made to the claims to determine the scope of the present invention.

Technology Classification (CPC): 0