One-Size Knee Replacement Doesn't Fit All

Poor wound healing, infection, loosening, fracture, nerve damage, dislocation, loss of motion, stiffness. This is just a small list of things that can go wrong with a total knee replacement (TKR). It sounds worse than it is. Only 0.2 percent of the adults having this surgery actually have implant failure. One rare cause isn't even on the list--having an implant put in that's too large for the knee.

The doctors of this report tell about two cases of oversized implant on the femoral side (upper half of the implant). In both cases, pain and loss of motion after surgery brought the patients back to their doctor. X-rays were used to diagnose the problem.

The large implants were taken out and a smaller implant was put back in. The result was a success for both patients. The authors conclude the success of any joint implant is based on preventing complications. The doctor's knowledge of implant design and operative technique are part of this success.

These doctors offer some advice to avoid the problems that come with an oversized implant. First, the implant must be properly sized. If the patient is between sizes, the doctor should choose the smaller one. Next surgeons are cautioned to make sure there is equal room in the joint for bending and straightening the knee. Finally if the patient ends up with an oversized implant that is causing problems, it may be best to replace it with a smaller one.

Reference: 

Chun-Sheng Lo, MD, et al. Knee Stiffness on Extension Caused by an Oversized Femoral Component after Total Knee Arthroplasty. In The Journal of Arthroplasty. September 2003. Vol. 18. No. 6. Pp. 804-808.

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