Patellofemoral arthroplasty conversion to total knee arthroplasty: An updated retrieval analysis and clinical outcomes.

Background: A prior retrieval analysis found high rates of infection after conversion of PFA to TKA, but was limited by a small sample size. The purpose of this study is to perform a retrieval analysis with clinical correlation on an expanded group of patients to better understand conversion of PFA to TKA.

Method: A retrospective review of an implant retrieval registry identified 62 conversions of PFA to TKA between 2004-2021. Implants were analyzed for wear pattern and cement fixation. Patient charts were reviewed for demographic information, perioperative data, prior and subsequent surgical procedures, complications and outcomes. Radiographs performed prior to index PFA and conversion procedures were assessed for KL grading.

Results: Cement fixation was present on 86% of retrieved components and wear was more pronounced on the lateral side. The most common indication for conversion to TKA was progression of OA in 46.8% of patients, followed by unexplained pain in the absence of radiographic or clinical changes (37.1%), loosening (8.1%), mechanical symptoms (4.8%), traumatic (3.2%). Thirteen patient experienced complications requiring additional procedures including arthrofibrosis (n = 4, 7.3%), PJI (n = 3, 5.5%), instability (n = 3, 5.5%), hematoma (n = 2, 3.6%) and loosening (n = 1, 1.8%). Revision components were used in 1.8% of cases and average post-conversion arc of motion was 119 degrees.

Conclusions: The most common reason for PFA conversion to TKA was progression of osteoarthritis. PFA conversion to TKA is technically similar to primary TKA, but complication rates are more consistent with revision TKA in this study.