Prosthetic replacement of the patellofemoral joint.

We are just beginning to fully appreciate the significant role of the patellofemoral joint in total knee replacement surgery. Most of the new generation prostheses have a flanged femoral component. The tendency is to make the flange more anatomic in shape as more attention is paid to patellar tracking. Most systems have an optional polyethylene button to resurface the patellar side of the patellofemoral joint, and indications for its use are increasing. Although pain relief with patellar buttons seems uniform, the potential complications of stress fracture, loosening, and wear must temper our enthusiasm for their use until there is longer follow-up. Vitallium hemiarthroplasty of the patella is available in prostheses with and without the requirement for cement fixation. Most investigators have good results in chondromalacia (as a secondary procedure), but the experience in the literature is small. Results have been poor when the femoral side of the joint has been involved. Metal to plastic isolated patellofemoral prostheses have been designed to treat disease on both sides of the patellofemoral joint or to salvage unflanged total knee replacements with residual patellofemoral symptoms. Short term experience has been promising.