Imaging Findings of Patellar Sparing Total Knee Arthroplasty

COPYRIGHT © 2022 BY THE JOURNAL OF BONE AND JOINT SURGERY, INCORPORATED. Introduction The practice of patellar resurfacing after a total knee arthroplasty (TKA) became commonplace during the 1990s and afterward. Yet to date, the practice of resurfacing is not standardized. The American Academy of Orthopedic Surgeon state that there is strong evidence for no differences in pain or function with patellar resurfacing. Yet, various reports denote the protective nature of resurfacing in maintaining articular cartilage thickness during a 5-year follow-up period. Patellar resurfacing is the fixation of a polyethylene dome onto the posterior patella to “reform” the articular interface between it and the femur (Fig. 1). The use of this technique allowed the native patella to articulate with the prosthesis in amore physiologic fashion than was possible with earlier implant designs. The improved patellar/ prosthetic kinematics allowed for a reduction in contact stresses that may contribute to postoperative anterior knee pain. In fact, this observation of increased contact stress between the native patella and the implant served as the impetus behind patellar resurfacing. Although patellar resurfacing demonstrated improvements in anterior knee pain relative to a nonresurfaced patella, the new practice presented unique patellar complications. Schindler et al. reported complications occurring in 4 to 35% of patellar resurfacing cases including patellar tilt, subluxation/dislocation of the patella, patellar component loosening, patellar fracture, and patellar avascular necrosis. In the modern era of TKA, orthopedic surgeons can often be categorized based on their approach to the patella: “nonresurfacers,” “universal resurfacers,” and “selective resurfacers”. Numerous randomized clinical trials and meta-analyses have not demonstrated a consistent benefit of patellar resurfacing during TKA.