Patent Publication Number: US-2005137708-A1

Title: Device and method of arthroscopic knee joint resurfacing

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application claims-priority from provisional patent application Ser. No 60/532,537, filed with the United States Patent and Trademark office on Dec. 23, 2003. The entire teachings of the said application are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
      Not Applicable.  
     REFERENCE TO MICROFICHE APPENDIX  
      Not Applicable.  
     BACKGROUND OF THE INVENTION  
      The present disclosure relates generally to knee replacement implants, and more particularly, but not necessarily entirely, to arthroscopic knee replacement implants for the femur and tibia.  
      It is common to provide implants to resurface worn articular surfaces of knees. The sizes of incisions required to insert the implants are often relatively large. Moreover, the prior art is characterized by several other disadvantages that are addressed by the present disclosure. The invention of the present disclosure minimizes, and in some aspects eliminates, numerous failures of the prior art, and other problems, by utilizing the devices described herein.  
     BRIEF SUMMARY OF THE INVENTION  
      A knee joint resurfacing implant including femoral and tibial implant components is disclosed. The femoral implant component includes an apex and supports on the proximal surface which are configured to share loads between cortical and cancellous bone material when the femoral implant component is implanted on the distal end of a prepared femur. The femoral implant may be attached to the femur using screws or other rigid members such as a peg, pin, or stem that traverses the external articulating surface and has a terminal surface that uniformly matches the external articulating surface of the implant. The tibial implant component of the knee replacement implant has a semicircular circumference, a concave superior surface, a planar inferior surface, and is divided into medial and lateral halves by a joint running longitudinally through the implant. The tibial implant component may be assembled within the knee joint. Accordingly, the femoral and tibial implant components may be configured and sized to be implanted using an arthroscopic surgical techniques and to permit the reduction of the size of skin incisions required for implantation.  
      The features and advantages of the disclosure will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by the practice of the disclosure without undue experimentation. The features and advantages of the disclosure may be realized and obtained by means of the instruments and combinations particularly pointed out in the appended claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The features and advantages of the disclosure will become apparent from a consideration of the subsequent detailed description presented in connection with the accompanying drawings in which:  
       FIG. 1  is a front view of a femoral implant in accordance with the principles of the present disclosure;  
       FIG. 2  is a side view of the femoral implant of  FIG. 1 ;  
       FIG. 3  is a cross-sectional view of the femoral implant taken along section A-A of  FIG. 2 ;  
       FIG. 4  is a top view of a tibial implant;  
       FIG. 5  is a side view the tibial implant of  FIG. 4 , as viewed from the lateral side;  
       FIG. 6  is an end view of the tibial implant of  FIG. 4 ; and  
       FIG. 7  is an exploded side view of a knee, including a femur, tibia, and patella, in which the femoral and tibial implants are installed. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      For the purposes of promoting an understanding of the principles in accordance with the disclosure, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the disclosure is thereby intended. Any alterations and further modifications of the inventive features illustrated herein, and any additional applications of the principles of the disclosure as illustrated herein, which would normally occur to one skilled in the relevant art and having possession of this disclosure, are to be considered within the scope of the disclosure claimed.  
      In describing and claiming the present disclosure, the following terminology will be used in accordance with the definitions set out below.  
      As used herein, the terms “comprising,” “including,” “containing,” “characterized by,” and grammatical equivalents thereof are inclusive or open-ended terms that do not exclude additional, unrecited elements or method steps.  
      Referring now to  FIG. 1 , a front view of a femoral implant  10  is shown. The femoral implant  10  may have one or more screw receiving holes  12  for receiving a screw  14  for attaching the femoral implant  10  to the distal end of the femur, as shown most clearly in  FIG. 7 . As shown in  FIG. 3 , which shows a cross-sectional view of the femoral implant  10  taken along the line A-A in  FIG. 2 , the femoral implant  10  may include a curved surface  16  configured for contacting a tibial implant  22  as shown in  FIG. 7 . The femoral implant  10  may also include an apex portion  18  and supports  20  to engage the prepared distal end of the femur. The apex portion  18  may be configured to be received in the cancellous bone material of the femur, whereas the supports  20  may be configured to contact the cortical bone material of the femur, so that load sharing between the cortical bone and the cancerous bone may be accomplished.  
      The femoral implant  10  may be used to repair a single condyle, referred to as a unicondylar replacement. Also, two femoral implants  10  may be used in a bi-condylar replacement within the scope of the present disclosure.  
      The femoral component  10  may be shaped to reproduce the weight bearing articular surface of the knee. The femoral component  10  may be configured to be 15-20 mm in width, for example, with an anatomical assortment of lengths and thicknesses. It will be understood that other widths and dimensions may be used within the scope of the present disclosure. Moreover, it will be understood that the femoral implant  10  may be implanted without resurfacing the entire width of the condyle. Accordingly, the femoral implant  10  may form a narrow rim on the condyle which may cooperate with the remaining portion of the condyle. The femoral component  10  may be made of a high molecular weight polyethylene (HMWPE) or any other suitable material known to those skilled in the art.  
      The screw receiving holes  12  may be formed of two distinct dimensions, as shown most clearly in  FIG. 2 , to allow for a cancellous type of screw to pass in order to provide fixation to the femur, with or without polymethylmethacrylate (PMMA) cement.  
      As shown in  FIGS. 4-7 , the tibial implant component  22  may be formed having a semicircular circumference. The tibial implant component  22  may have a concave superior surface  24  and a planar inferior surface  26 . The tibial implant component  22  may be divided into a medial portion  28  and a lateral portion  30  by an implant joint  32 . The implant joint  32  may allow the tibial implant component  22  to be inserted into the knee joint in separate pieces through an arthroscopic portal and then assembled within the knee joint at the time of implantation under arthroscopic visualization. It will be understood that the implant joint  32  may be in the form of a dovetailed joint with a projection  34  on the lateral portion  30  and a channel  36  on the medial portion  28 , or the projection  34  may be formed on the medial portion  28  and the channel  36  may be on the lateral portion  30 . It will also be appreciated that other types of junctions or interlocking geometric interfaces may be used within the scope of the present disclosure. Moreover, the implant joint  32  may be self locking and may include any of a variety of fasteners or attaching devices to prevent the medical portion  28  and the lateral portion  30  from becoming separated.  
      It will be understood that the tibial implant  22  may be formed of metal, polymer, or any other suitable material known to those skilled in the art.  
      The tibial implant component  22  may be attached to the tibia to prevent migration of the tibial implant component  22  with respect to the tibia, or the tibial implant component  22  may be free floating on the tibia. The tibial implant component  22  may be cemented in place using an access channel  38  passing obliquely from the anterior proximal tibia into the central aspect of the tibial plateau as illustrated in  FIG. 7 . The access channel  38  allows cement to be placed on the tibial implant  22  in a manner to avoid unwanted spreading of the cement. Moreover, a strand or other tensioning device may optionally be placed in the access channel  38  and attached to the tibial implant component  22  by any suitable means. The strand may be a suture or any other mechanism known to those skilled in the art. Similarly, any variety of cement known to those skilled in the art may be installed through the access channel  38 .  
      As shown in  FIG. 7 , which shows an exploded side view of a knee, including the femur, tibia and patella, in which the femoral implant component  10  and tibial implant component  22  are implanted, the convex curved surface  16  of the femoral implant component  10  may be configured to fit in the concave superior surface  24  of the tibial implant component  22 . The inferior surface  26  of the tibial implant component  22  as shown in  FIG. 5  is configured to mate to the proximal surface of the tibia as shown in  FIG. 7 , and the superior surface  24  of the tibial implant component  22  is configured to mate and articulate with the distal convex curved surface  16  of the femoral component  10  in a conformational relationship. Thus, the size and shape of the tibial implant  22  and femoral implant  10  and their articulating surfaces may vary to conform to a desired anatomical structure. In one embodiment of the tibial implant  22 , the tibial implant  22  may be thicker on the medial side  28  than on the lateral side  30 .  
      Orientation of the mechanical axis of the knee joint, and the depth and position of cuts made to the native surface of the knee prior to implant insertion may be facilitated by the use of a surgical navigation system that may include immediate real time data acquisition and retrieval.  
      The present disclosure provides surgeons and patients with a reliable and technical method and implants to appropriately resurface the worn articular surface of a single knee compartment. The design of the instruments and implants may allow skin incisions to be less than 25 mm in length. The procedure may be performed arthroscopically with surgical navigational assist.  
      In the foregoing, various features of the present disclosure are grouped together in a single embodiment for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed disclosure requires more features than are expressly recited in each claim. Rather, as the claims will reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment.  
      It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present disclosure. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present disclosure and the appended claims are intended to cover such modifications and arrangements. Thus, while the present disclosure has been shown in the drawings and described above with particularity and detail, it will be apparent to those of ordinary skill in the art that numerous modifications, including, but not limited to, variations in size, materials, shape, form, function and manner of operation, assembly and use may be made without departing from the principles and concepts set forth herein.