Patello-femoral arthroplasty

The Polycentric knee design, as originally conceived by Gunston, did not address the patello-femoral joint. Gunston mentions in his 1971 paper that the patella may be retained because no impingement of the patella on the prosthesis 

Gunston and MacKenzie s response to severe patello-femoral pain was to develop a separate patello-femoral arthroplasty, which consisted of a metallic patellar button articulating against an UHMWPE track implanted in the femur (1976). Because this solution required the implantation of two additional components, they cautioned against using this solution for patello-femoral replacement indiscriminately (1976). 

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Within this context, the patello-femoral arthroplasty offered by the Total Condylar Knee was a far more elegant... 

Ranawat C.S., H.A. Rose, and W.J. Bryan. 1984. Replacement of the patello-femoral joint with the total condylar knee arthroplasty. Int Orthop 8 61-65. 

Abstract— There are little attention given for Patello-femoral joint s design although it is highly loaded part of a total knee arthroplasty. Finite element method proved the poor design leads to excessive stresses within the polyethylene of the patellar unit during flexion of the knee. In this study, patellar prosthesis with more suitable with the femoral unit than the other design tested were developed. The experiment done has proved that the use of patella and femoral models developed can be use to predict the contact area between them. 

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