Abstract:
A provisional prosthetic system that replicates the characteristics of a corresponding, nonprovisional femoral prosthesis. The provisional prosthetic system may include a frame component and a shell component. The frame component of the provisional prosthetic system may be configured to be attached directly to a resected femur. In one exemplary embodiment, the frame component is impacted onto the resected femur to firmly seat therewith. Once the frame component is secured to the resected femur, a shell component of the provisional prosthetic system may be positioned on and secured to the frame component. In one exemplary embodiment, the frame component is made from a metallic material. This allows for the frame component to maintain the rigidity necessary to facilitate proper trialing. In another exemplary embodiment, the shell component is a plastic.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a provisional prosthetic system and the surgical methods for utilizing the same. 
         [0003]    2. Description of the Related Art 
         [0004]    Prostheses are commonly utilized to repair and/or replace damaged bone and tissue in the human body. For example, a knee prosthesis may be implanted to replace damaged or destroyed bone in the tibia and/or femur and to recreate the natural, anatomical articulation of the knee joint. To implant a prosthesis, orthopedic surgery is performed which requires the creation of an incision in the skin of the patient and may necessitate the retraction of surrounding tissue to provide the surgeon with access to the surgical site. 
         [0005]    To facilitate the implantation of a prosthesis, modular prostheses may be utilized. Modular prostheses have several individual, distinct components which are connected together to form the final, implanted prosthesis. For example, a modular knee prosthesis may include individual femoral, tibial, and patellar components which are connected together to form the final, implanted knee prosthesis. Additionally, one component, e.g., a femoral implant in a modular knee prosthesis system, may be selected from several different femoral components having various configurations, all of which are included in the modular prosthesis system. By selecting the femoral component that best accommodates an individual patient&#39;s anatomy, the surgeon may assemble a prosthesis that more closely approximates the natural anatomy of the patient. 
         [0006]    In addition to the final, implanted components of a modular prosthesis system, a modular prosthesis system may also include provisional components which replicate the size and shape of the final, implanted components of the modular prosthesis system. The use of provisional components provides the surgeon with the ability to test the ultimate configuration of the prosthesis prior to the implantation of the final components. By trialing, i.e., testing, the surgeon is able to determine whether the fit, alignment, and range of motion provided by the final prosthesis will approximate the patient&#39;s natural anatomy. Additionally, as many implants achieve some measure of press fit with the resected bone, it is important that the provisional components maintain similar stiffness to the implant so that implant fit to bone can be checked prior to implantation. To ensure that the provisional components accurately replicate the function of the final, implanted components, the provisional components are dimensionally equivalent to the implanted components and are frequently manufactured from the same material. 
       SUMMARY 
       [0007]    The present invention relates to a provisional prosthetic system and the surgical methods for utilizing the same. In one embodiment, the provisional prosthetic system replicates the characteristics of corresponding, nonprovisional femoral prostheses. In this embodiment, the provisional prosthetic system includes a frame component and a shell component. The frame component of the provisional prosthetic system may be configured to be attached directly to a resected femur. In one exemplary embodiment, the frame component is impacted onto the resected femur to firmly seat therewith. Once the frame component is secured to the resected femur, the shell component of the provisional prosthetic system may be positioned on and secured to the frame component. In one exemplary embodiment, the frame component is made from a metallic material. This allows for the frame component to maintain the rigidity necessary to facilitate proper trialing. In another exemplary embodiment, the shell component is a plastic. In yet another exemplary embodiment, the shell component is fabricated by injection molding. 
         [0008]    To ensure that a provisional and, ultimately, a nonprovisional that has the characteristics most suited for an individual patient are selected, the provisional prosthetic system may include a plurality of shell components having different characteristics, e.g., different sizes, orientations, and/or designs that correspond to available nonprovisional prostheses. For example, if the prosthesis includes three different nonprovisional implants having different sizes, three provisional implants would be included in the prosthesis system which correspond in size to the three nonprovisional implants. Thus, a surgeon may attach a first shell component to the frame component of the provisional prosthetic system and trial, i.e., test, the same. If the surgeon is not satisfied with the results of the current shell component, the surgeon may remove the shell component from the frame component and attach a different shell component having different characteristics, until the best fit for an individual patient is identified. 
         [0009]    By utilizing the provisional prosthetic system of the present invention, numerous benefits are realized. For example, by utilizing the frame component and shell component design of the present system, only a single frame component is attached to the resected femur. Thus, the need to impact and remove various provisional components from the resected bone is eliminated and wear of the natural bone stock during the trialing of the provisional components is lessened. Additionally, by eliminating the need to manufacture the shell components of the provisional prosthetic system from a metallic material, the weight of the full complement of provisional components is substantially lessened. This decreases the burden on operating room personnel and hospital staff to stock, inventory, clean, and transport the full complement of provisional components. Moreover, by manufacturing the shell components of the present provisional system from plastic, for example, the cost of producing the same is decreased. 
         [0010]    Further, because a plurality of different shell components may be attached to a single frame component, the total number of provisional components in any given provisional system may be decreased. For example, in an implant system having femoral components for standard size, plus size, and minus size for each of the left knee and the right knee, a single frame component may be designed to accept all six configurations of the corresponding shell components. Thus, a single frame can be combined with the differing shell components to form provisional components that accurately replicate the characteristics of the six corresponding nonprovisional implants. 
         [0011]    By providing a full complement of provisional components having a mass and volume substantially less than that of a complement of standard provisional components, a hospital may be more likely to stock the entire system. Additionally, a surgeon may request the entire complement of components in the operating room and thus the surgeon may be able to achieve better extension and flexion gap balancing, without the need to perform additional bone cuts or to extensively test the flexion and extension gaps. 
         [0012]    In one form thereof, the present invention provides a modular provisional system, including a frame component configured to be secured to the distal end of a femur; and a shell component configured to be releaseably secured to the frame component, the frame component and the shell component cooperating to form a provisional implant which replicates the characteristics of at least one nonprovisional component of a prosthesis system. 
         [0013]    In another form thereof, the present invention provides a modular provisional system, including a frame component having first engagement structure, the frame component configured for securement to the distal end of a femur; and a shell component having a frame contacting surface and an articulation surface, at least a portion of the frame contacting surface configured to engage the first engagement structure of the frame component to secure the shell to the frame, the articulation surface of the shell component shaped to replicate natural femoral condyles, wherein the frame component and the shell component cooperate to replicate a characteristic of at least one nonprovisional component of a prosthesis system. 
         [0014]    In another form, thereof the present invention provides a method of trialing a femoral implant including the steps of attaching a frame component to the distal end of a femur; attaching a shell component having an articulation surface to the frame component, wherein the frame component and the shell component cooperate to form a first provisional implant; trialing the first provisional implant formed by the frame component and the shell component. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0016]      FIG. 1  is an exploded perspective view of one embodiment of the provisional prosthetic system and depicting a resected femur; 
           [0017]      FIG. 2  is another perspective view of the embodiment of  FIG. 1 , taken from a posterior aspect; 
           [0018]      FIG. 3  is another perspective view of the embodiment of  FIG. 1  taken from a medial aspect; 
           [0019]      FIG. 4  is an exploded perspective view of the provisional prosthetic system according to another exemplary embodiment; and 
           [0020]      FIG. 5  is an assembled, perspective view of the provisional prosthetic system of  FIG. 4 ; 
           [0021]      FIG. 6  is a partial assembled view of the provisional prosthetic system of  FIG. 1 ; and 
           [0022]      FIG. 7  is an assembled view of the provisional prosthetic system of  FIG. 1 . 
       
    
    
       [0023]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrates preferred embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention any manner. 
       DETAILED DESCRIPTION 
       [0024]    As shown in  FIGS. 1-3 , femoral provisional  10  includes frame component  12  and shell component  14 . Shell component  14  may be attached to frame component  12 , as shown in  FIG. 7 , to form assembled femoral provisional  10 , as described in detail below. Referring to  FIGS. 1-3 , frame component  12  of femoral provisional  10  is configured for direct attachment to femur  16 . As shown in  FIG. 1 , femur  16  includes resected distal end  18  having apertures  20  and cutout  22  formed therein. Resected distal end  18  of femur  16  is fully resected, i.e., all of the cuts necessary for implantation of a final, nonprovisional femoral component have been made. In another exemplary embodiment, resected distal end  18  may include only a portion of the cuts necessary to facilitate implantation of the final, nonprovisional femur component. In this embodiment, femoral provisional  10  may be utilized to facilitate a surgeon&#39;s determination of the location for making the remaining cuts to femur  16 . 
         [0025]    In one exemplary embodiment, frame component  12  is formed from a metallic material, e.g., formed from a metal, a metal alloy, or a material having properties that are substantially similar to a metal or metal alloy. This provides frame component  12  with the necessary rigidity to represent the rigidity of the corresponding nonprovisional component on the resected bone and retain shell component  14  in the proper position during trialing. Frame component  12  of femoral provisional  10  includes bone contacting surface  24  and posts  26 , best seen in  FIG. 2 . Bone contacting surface  24  of frame component  12  is shaped to mate with resected distal end  18  of femur  16  and posts  26  are sized to be received within apertures  20 . Apertures  20  of femur  16  may be formed by drilling, reaming, or any other known technique. Apertures  20  are sized slightly larger than posts  26 , but are close enough in size to posts  26  that frame component  12  may be impacted to be properly seated on distal end  18  of femur  16 . While frame component  12  is described and depicted herein as including posts  26 , posts  26  are not necessary to the function of frame component  12  and further embodiments are envisioned in which posts  26  are absent. 
         [0026]    Frame component  12  further includes shell contacting surface  27  having condylar bases  28 ,  30  connected by anterior bridge portion  32  and posterior bridge portion  34  ( FIG. 3 ). In one exemplary embodiment, posterior bridge portion  34  replicates the cam of a Posterior Stabilized femoral implant. In another exemplary embodiment configured for a Posterior Cruciate Ligament Retaining femoral prosthesis, posterior bridge portion  34  is absent. Additionally, ribs  36 ,  38  extend from shell contacting surface  27  of frame component  12  to add rigidity and facilitate retention and alignment of shell component  14  upon frame component  12 , as discussed in detail below. 
         [0027]    Referring to shell component  14 , shell component  14  includes posterior overhang  42 , anterior overhang  43  ( FIG. 2 ), and frame contacting surface  40  forming condylar recesses  44 . Condylar recesses  44  are separated from overhangs  42 ,  43  by tapered leads  46 ,  47 , respectively, which facilitate attachment of shell component  14  to frame component  12 . In one exemplary embodiment, shell component  14  is formed from a plastic. For example, shell component  14  may be formed from an injection molded polymer. By forming shell component  14  from a plastic or other polymer, the weight of shell component  14  and, correspondingly, femoral provisional  10  is significantly reduced. Thus, a full complement of provisional components made in accordance with the present invention is significantly lighter than a full complement of standard provisional components, lessening the burden on operating room personnel and hospital staff who must transport the same. 
         [0028]    Shell component  14  also includes articulating surface  48  having condylar portions  50 ,  52  connected by anterior portion  54 . Referring to  FIG. 2 , shell component  14  further includes grooves  56 ,  58  extending through frame contacting surface  40  and overhang  43 . Grooves  56 ,  58  are configured to receive and retain ribs  36 ,  38  of frame component  12 , respectively, therein. Additionally, both grooves  56 ,  58  include an indentation (not shown) configured to matingly engage ribs  36 ,  38 , respectively. Thus, receipt of ribs  36 ,  38  within the indentations of grooves  56 ,  58  provide for retention of anterior portion  54  of shell component  14  upon anterior bridge portion  32  of frame component  12 . In one exemplary embodiment, the engagement of ribs  36 ,  38  with grooves  56 ,  58  forms a snap-fit connection. Moreover, ribs  36 ,  38  and grooves  56 ,  58  facilitate the alignment and seating of shell component  14  with frame component  12  prior to attachment. 
         [0029]    Referring to  FIGS. 1-3 , condylar recesses  44  ( FIGS. 1 and 2 ) of shell component  14  are configured to receive portions of condyle bases  28 ,  30  of frame component  12  therein. Specifically, condylar recesses  44  and tapered lead  46  are configured to engage posterior portions  60 ,  62  and tapered edge  64  ( FIG. 2 ), respectively. Thus, posterior portions  60 ,  62  and condylar bases  28 ,  30  of frame component  12  are in posterior mating engagement with condylar recesses  44  and tapered lead  46  of shell component  14 . In one exemplary embodiment, the interaction of condylar recesses  44 , tapered lead  46 , posterior portions  60 , 62  and tapered edge  64  forms a snap-fit connection. To remove shell component  14  from frame component  12 , a surgeon simply lifts up on anterior portion  54  of shell component  14 , for example, to release the snap-fit connection. Shell component  14  may then be replaced by another shell component  14  having different characteristics. 
         [0030]    To assemble femoral provisional  10  upon femur  16 , femur  16  is initially resected, as described above, to form resected distal end  18 . Apertures  20  are then formed in resected distal end  18  of femur  16  and sized to receive post  26  of frame component  12  therein. In one exemplary embodiment, frame component  12  is selected from a plurality of frame components having different characteristics. With post  26  aligned with apertures  20 , frame component  12  is impacted onto resected distal end  18  of femur  16  until bone contacting surface  24  is in mating engagement with resected distal end  18 , as shown in  FIG. 6 . Referring to  FIGS. 6 and 7 , once frame component  12  is securely seated on femur  16 , one of a plurality of shell components  14  having characteristics which a surgeon believes would best accommodate a patient&#39;s natural anatomy is aligned with and secured to frame component  12 , as described in detail above. Alternatively, one of a plurality of shell components  14  may be secured to frame component  12  prior to seating frame component  12  on femur  16 . Thus, once frame and shell components,  12 ,  14  are secured together, the assembly is impacted on femur  16  as described above. With shell component  14  secured to frame component  12  and, correspondingly, femur  16 , a surgeon may perform trialing of femoral provisional  10 . 
         [0031]    In the event the surgeon determines that femoral provisional  10  satisfactorily replicates the patient&#39;s natural anatomical movement, shell component  14  may be removed from frame component  12  and frame component  12  removed from femur  16 . A nonprovisional femoral component having characteristics which correspond to femoral provisional  10  is then implanted using standard surgical techniques. 
         [0032]    In the event a surgeon determines femoral provisional  10  does not satisfactorily replicate a patient&#39;s natural anatomical movement, shell component  14  may be removed from frame component  12 , which provides the sole securement of shell component  14  to femur  16  as described in detail above, and a different shell component  14  having different characteristics may be attached to the same frame component  12 . By using a single frame component  12  capable of attachment to multiple shell components  14 , the need to impact and remove various frame components  12  is eliminated. Thus, wear of resected distal end  18  of femur  16  is lessened. Additionally, by providing for attachment of multiple shell components  14  to a single frame component  12 , the total number of components is lessened. The surgeon may then trial the new femoral provisional  10 . Once a surgeon has identified the one of a plurality of shell components  14  that would satisfactorily replicate the patient&#39;s natural anatomical movement, femoral provisional  10  may be removed from femur  16 , as described in detail above, and the corresponding nonprovisional femoral component implanted. 
         [0033]    Referring to  FIG. 4 , another exemplary embodiment of frame component  12  and shell component  14  are depicted as frame component  70  and shell component  72 . Frame component  70  and shell component  72  include several components which are identical or substantially identical to components of frame component  12  and shell component  14 , respectively, and corresponding reference numerals are used to identify identical or substantially identical components therebetween. As shown in  FIG. 4 , frame component  70  includes openings  74  formed in condylar bases  28 ,  30  and anterior bridge portion  32 . Similarly, shell component  72  includes projections  76  formed on condylar portions  50 ,  52  and anterior portion  54 . Projections  76  are sized and configured to be received with openings  74  of frame component  70 . Thus, as shown in  FIG. 5 , receipt of projections  76  of shell component  72  within openings  74  of frame component  70  provides a snap-fit connection between frame component  70  and shell component  72 . 
         [0034]    To separate frame component  70  and shell component  72 , a surgeon may exert a force on anterior portion  54  of shell component  72 , in a direction away from frame component  70 , to disengage one of projections  76  from one of openings  74 . Once shell component  72  is removed from frame component  70 , a different shell component  72  having different characteristics may be attached to frame component  70  in a similar manner. In another exemplary embodiment, frame component  70  may include a projecting rib and shell component  72  a corresponding groove to facilitate alignment of frame component  70  and shell component  72  to facilitate proper seating and retention of shell component  72  on frame component  70 . 
         [0035]    While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.