Patellar Resurfacing in Total Knee Replacement: Five-Year Clinical and Economic Results of a Large Randomized Controlled Trial The Journal of Bone & Joint Surgery, Volume 93, Issue 16 Suzanne Breeman, PhD; Marion Campbell, PhD; Helen Dakin, MSc; Nick Fiddian, MD; Ray Fitzpatrick, PhD; Adrian Grant, DM; Alastair Gray, PhD; Linda Johnston, MSc; Graeme MacLennan, MSc; Richard Morris, PhD; David Murray, MD, FRCS; Synopsis Background: There is conflicting evidence regarding the merits of patellar resurfacing during total knee arthroplasty, as many of the previous randomized controlled trials have not been adequately powered. Methods: A pragmatic, multicenter, randomized controlled trial was initiated in 1999 in the United Kingdom. Within a partial factorial design, 1,715 patients were randomly allocated to receive or not receive patellar resurfacing during total knee arthroplasty. The primary outcome measure was the Oxford Knee Score; secondary measures included the Short Form-12, the EuroQoL 5D, cost, cost-effectiveness, and the need for subsequent knee surgery. Results: There was no significant difference between the groups with respect to the mean Oxford Knee Score or any other outcome measure at five years postoperatively. There was no significant difference between the two groups with respect to the prevalence of knee-related readmission, of minor or intermediate reoperation, or of subsequent patella-related surgery. The total health care cost for the primary arthroplasty, subsequent monitoring, and any revision surgery did not differ significantly between the two groups. Conclusions: In the largest randomized controlled trial of patellar resurfacing reported to date, the functional outcome, reoperation rate, and total health care cost five years after primary total knee arthroplasty were not significantly affected by the addition of patellar resurfacing to the surgical procedure. Introduction Total knee arthroplasty is a common surgical procedure. Long-term observational studies have indicated that more than 90% of modern primary total knee replacements survive for at least fifteen years. However, a substantial proportion of patients have a poor functional result and persistent knee pain. Many of these poor results are attributed to problems arising from the patellofemoral joint, and there is considerable debate regarding whether the patella should be resurfaced at the time of the primary total knee arthroplasty. Materials and Methods The trial was approved by the relevant national and local research ethics committees and was registered in a public trials registry (International Standard Randomized Trial No. ISRCTN45837371). Any orthopaedic surgeon in the United Kingdom who performed knee replacements regularly was eligible to participate in the trial. One hundred and sixteen surgeons in thirty-four centers in the United Kingdom participated in the KAT study, and ninety-nine (85%) of these surgeons recruited patients to the patellar resurfacing comparison. The primary outcome measure was the functional status as measured with use of the Oxford Knee Score (OKS), which was developed specifically to measure outcomes of knee replacement and has been shown by independent studies to perform well compared with alternative outcome instruments. In addition, question 12 of the OKS was analyzed in isolation as a secondary outcome since it assesses the ability to walk downstairs, which is one aspect of knee function that patellar resurfacing may influence. The five possible responses for question 12 were "No, impossible" (scored as 0), "With extreme difficulty" (1), "With moderate difficulty (2), "With little difficulty" (3), and "Yes, easily" (4). Results From July 1999 to January 2003, 4,070 potentially eligible patients were identified and 2,374 (58%) gave their consent and were randomized for treatment. Of these, 1715 patients were suitable for the comparison assessing patellar resurfacing. Of the 1,715 patients formally enrolled in the trial comparison, 1,424 (83%) received the allocated procedure. There was no statistically significant difference between the groups either in the overall rate of short-term complications or in any of the patient-assessed outcomes at baseline or at any subsequent time point. The mean OKS value in both groups increased from 18 points preoperatively to 35 points at five years postoperatively. An analysis of outcomes according to the femoral component shape (whether or not the trochlear groove was appropriate for an anatomical or a domed patella) revealed no statistically significant differences. The percentage of patients who required readmission and/or further intervention was 12.1% in the patellar resurfacing group compared with 13.1% in the nonresurfacing group; 4.4% of the patellar resurfacing group and 5.8% of the nonresurfacing group required further minor or intermediate surgical procedures; 1.6% of the patellar resurfacing group and 2.9% of the nonresurfacing group required further major surgical procedures; and 1.0% of the patellar resurfacing group and 1.9% of the nonresurfacing group had further patella-related surgery. The reasons for further knee surgery included infection, knee pain, knee stiffness, implant loosening, and knee instability. The proportion of patients requiring further surgery did not differ significantly between the patellar resurfacing and nonresurfacing groups for any of the individual levels of secondary procedures. During the first five postoperative years, 0.8% of the patellar resurfacing group and 1.9% of the nonresurfacing group had late patellar resurfacing . Discussion The results of the current study indicate that patient functional status, patient quality of life during the first five years after total knee arthroplasty are not significantly affected by the addition of patellar resurfacing to the initial surgical procedure. The 95% confidence interval for the difference in the OKS between the patellar resurfacing group and the nonresurfacing group was 0.6 to 1.8 at five years postoperatively. In conclusion, on the basis of five years of follow-up, there is no clear benefit to resurfacing the patella during total knee arthroplasty, as resurfacing had no significant effect on patient functional status or patient quality of life.