The Outerbridge Classification Predicts the Need for Patellar Resurfacing in TKA

Abstract

Patellar resurfacing (PR) in total knee arthroplasty (TKA) is controversial. The Outerbridge classification of cartilage defects in the patella is commonly used in the literature. The purpose of this study was to determine if the Outerbridge classification can predict the need for PR as part of total knee arthroplasty. Between 1995 and 2000, we performed a prospective, randomized study of 500 TKAs. We carried out PR depending on the Outerbridge classification of the patella at the time of surgery. Patients with Outerbridge Grades I, II, and III formed Group A, whereas patients with Grade IV formed Group B. Within each group, resurfacing was completed on half of the patients. Group A had 328 patients (164 with PR, 164 without PR). In Group B, there were 172 patients (86 with PR, 86 without PR). An identical prosthetic design was used for both groups. The minimum followup was 5 years (average, 7.8 years) for both Group A and Group B. At the end of followup, we assessed the number of patients in each group that required secondary resurfacing as a result of patellofemoral pain. Patients in Group A required fewer revisions for PF pain. In Group A, only one patient required a secondary PR (0.6% rate), whereas in Group B, 10 patients needed PR (11.6% rate). In Group B, the risk of need of a patellar resurfacing was 21.5 times greater than in Group A. On the basis of these findings, we recommend PR in Outerbridge Grade IV patellae, but not in Grades I, II, and III. Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.