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The Patellar Problem with New Knee Joints

Total knee replacements (TKR) are fairly common these days. Doctors use many different types of implants. Each new joint implant has several parts: the top half (femoral component), the bottom half (tibial component), and the kneecap (patellar component).

Sometimes one or more of these parts will fail, resulting in a second operation to correct the problem. Often only the patellar component fails. Not much is known about why this happens. Some doctors think it's a combination of the way the implant is made and the way the operation is done.

Doctors at a leading medical center in Chicago are studying this problem. They found that even after replacing it, the patellar portion doesn't work well. In fact, almost 40 percent of the knees that had patellar revision failed a second time. The patients had painless squeaking, swelling, and trouble walking long distances.

Many changes have already been made in the design of these implants. For example, the metal backing on the patellar piece is now made of plastic. The surgeons have also changed the way the bone is turned during the operation.

Unsuccessful revision can be disappointing to the patient and the doctor. The authors of this study advise doctors to look at the problem carefully before operating a second time. More studies are needed to increase the success of this operation.

References: Seth S. Leopold, MD, et al. Isolated Revision of the Patellar Component in Total Knee Arthroplasty. In The Journal of Bone and Joint Surgery. January 2003. Vol. 85-A. No. 1. Pp. 41-47.

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