Patellofemoral contact areas in total knee arthroplasty

Failures after total knee arthroplasty often are caused by problems of the patellofemoral articulation. We investigated 10 different femoral component s and 12 different patellar implants. The size of the patellofemoral contac t areas was evaluated by pressure sensitive films every 10 degrees up to 90 degrees of flexion. The farces of the quadriceps muscle and the patella li gament were measured by force transducers. The compressive forces acting be tween patella and gliding grove were calculated, The geometry of the compon ents and forces was documented. The retropatellar contact areas are specific for each prosthesis. The patte rns of displacement are similar for some groups of prostheses. The absolute size of the contact areas and their size relative to the total surface of the patellar implant is very small. This induces high local pressure of the polyethylene.