Total knee replacements have been proven to last at least 15 years. But survival of the implant and knee function are too different things. And many total knee patients report persistent knee pain and loss of function despite the new knee.
Surgeons are exploring the reasons for this dilemma and looking for ways to improve results. One of those ways is to resurface the patella (knee cap) as part of the knee replacement procedure.
Resurfacing the patella involves shaving and smoothing the cartilage and bone along the back of the patella. Then the surface is covered with an implant made of metal, polyethylene (plastic), or a combination of both metal and polyethylene. Many surgeons favor the all-polyethylene backing as a result of studies that have shown there are fewer problems with it.
The present study was done to see if patellar resurfacing made any real difference. It was part of a larger study investigating the results of using four different total knee replacements. The larger study is called the Knee Arthroplasty Trial (KAT).
With over 1700 patients enrolled in the KAT study, this may be the largest research project looking at patellar resurfacing. Half the patients got a knee replacement with patellar resurfacing while the other half received the knee implant but did not have the patella resurfaced.
Results were compared between the two groups using pain, motion, and function as the main measures. There are several tests that give objective data to compare. The authors used the Oxford Knee Score, the Short-Form-12, and the EuroQoL 5D. They also looked at costs and compared the number of patients in both groups who had to have a revision (second) surgery.
After all the data was in and the number crunching was done, there was no difference between the two groups. After five years, presence of pain, pain levels, and the quality of life based on knee function were about the same for all patients in both groups.
Number and type of complications were also similar enough to be considered "no significant difference" between the two groups. And costs associated with the two procedures were fairly equal. There was a slight increase in charges because of the added patellar implant and slightly longer time in the operating room. But the statistical difference wasn't enough to be considered significant.
What can we take away from the results of this study? Basically, that there is no detectable difference in clinical results between having a total knee replacement with or without patellar resurfacing.
The large number of patients involved in the study help support this idea that there is no obvious benefit of patellar resurfacing at the time of the knee replacement procedure. Surgeons may want to reserve patellar resurfacing for patients who continue to experience knee pain after knee replacement. Resurfacing the patella is a simple revision procedure that can be done later if needed.
Reference: Suzanne Breeman, PhD, et al. Patellar Resurfacing in Total Knee Replacement: Five-Year Clinical and Economic Results of a large Randomized Controlled Trial. In The Journal of Bone and Joint Surgery. August 17, 2011. Vol. 93A. No. 16. Pp. 1473-1481.