Hip and knee replacements are fairly common for osteoarthritis today. But what about the patient with arthritis of the patellofemoral joint (kneecap)? In this study surgeons report the results of using a custom-made patellofemoral implant for 25 patients with isolated patellofemoral arthritis. All patients were 55 years old or younger.
The anatomy of the patellofemoral joint is very different from patient to patient. Off-the-shelf implants have never worked well for this problem. Custom made implants to fit the patient’s own curves and grooves may be the answer.
In this study a computer program was combined with CT scan to map out a three-dimensional (3-D) model of each patient’s knee. Information about the femoral groove was used to build a custom cobalt-chromium implant. The femoral groove is located on the lower end of the femur (thigh bone). A healthy patella moves smoothly in this groove. Arthritic changes can wear away the smooth surface of this groove.
At the end of three years, all 25 implants were in place and working just fine. The computer technology allowed a custom fit to avoid removing the bone. The implant realigns the knee. It puts the patella in the correct position to improve function of the quadriceps muscle.
The cost of the implant is about 15 to 30 per cent more than the price of a ready made patellofemoral implant. It takes about eight weeks to manufacture.
The authors conclude custom patellofemoral replacement is worth the price for some patients. Young, active adults with isolated and severe patellofemoral arthritis benefit the most. The entire knee joint can be replaced later if necessary. Long-term results of the patellofemoral implant are still being studied.