Doctors Tip Their Caps During Knee Joint Revision Surgery

Sometimes knee joint replacements fail. There can be loosening of the implant, fractures of the bone, or lingering knee pain. The implant may have to be removed and replaced with another one. Each knee joint replacement has three main parts. There's an upper piece called the femoral component. The lower half is called the tibial component. The third part is the kneecap or patellar component.

What if the implant has failed and there's nothing wrong with the patellar component? Does the patellar part have to be removed and replaced, too? Doctors at four centers in Philadelphia, Baltimore, and Boston studied this question. No one really knows how long these components last, but the old saying, "If it isn't broke, don't fix it," might be good advice in these cases.

The records of all patients in these centers who had a total knee revision were reviewed. Only patients whose patellar part was left untouched during the revision surgery were included. The researchers found that if the kneecap was in the right place and not loose, there was no reason to remove and replace it.

The authors of this study also report that any failures of the patellar component may be caused by something else. They found that the method used to sterilize this part makes a difference. This process takes place at the manufacturing plant when the implant is made.

According to these findings, doctors should contact the manufacturer before removing or replacing the patella. The method of sterilization should be determined before a second operation. If gamma sterilization in air is the method used, then the authors suggest that the patellar component be replaced. Otherwise, the authors advise doctors to leave it alone.



References: Jess H. Lonner, MD, et al. Fate of the Unrevised All-Polyethylene Patellar Component in Revision Total Knee Arthroplasty. In The Journal of Bone and Joint Surgery. January 2003. Vol. 85-A. No. 1. Pp. 56-59.