Isolated revision of the patellar component in total knee arthroplasty

Background: Problems with the patellofemoral articulation are the most common causes of failure after total knee arthroplasty. However, there are few reports describing outcomes following isolated revision of the patellar component. Methods: Forty knees with a Miller-Galante I prosthesis underwent isolated patellar revision (with or without lateral retinacular release). The Hospital for Special Surgery knee scores were collected prospectively, and radiographs made preoperatively and at the time of the final follow-up were analyzed with respect to alignment, component position, and patellar tracking. Particular attention was given to patients who had a reoperation or repeat revision and who had clinical or radiographic evidence of failure of the patellar revision. Results: At a mean follow-up of sixty-two months, fifteen (38%) of the forty knees that had had an isolated revision of the patellar component failed a second time. Eight of them required a total of twelve additional operations at a mean of forty-nine months after the patellar revision. Three of the failures were severe enough to require revision of two or more of the components. Of the twenty-five knees that had not failed, the average Hospital for Special Surgery knee score at the time of the final follow-up was 87 points. Of the seven knees that did not undergo reoperation but were deemed to be failures on the basis of the patients' symptoms, the average Hospital for Special Surgery knee score at the time of the final follow-up was 72 points. Conclusions: Isolated patellar revision, with or without concurrent lateral retinacular release, was associated with a high rate of reoperation and a relatively low rate of success. Elements of the implant design and component alignment contributed to the patellar component failure; both should be scrutinized carefully in patients who are seen with this problem, prior to proceeding with isolated revision of the patellar component of a total knee arthroplasty. Level of Evidence: Therapeutic study, Level IV (case series [no, or historical, control group]). See p. 2 for complete description of levels of evidence.