The Impact of Patellar Position on Mediolateral Joint Gap in Cruciate-Retaining and Posterior-Stabilized Total Knee Arthroplasty: A Prospective Study

This prospective study aimed to investigate the influence of patellar position (ie, eversion, lateralization, and reduction) on medial and lateral gap measurements during total knee arthroplasty (TKA) in both cruciate-retaining (CR) and posterior-stabilized (PS) TKA designs.The present work analyzed 50 knees with primary osteoarthritis that underwent TKA between July and November 2019. Medial and lateral gaps were measured at different knee flexion angles (0°, 45°, 90°, and 120°) in 3 patellar positions after sequentially inserting CR type and PS type trial component in the same knee.In CR TKA, medial gaps in patellar reduction showed significantly smaller gaps at 90° and 120° of knee flexion compared to those in eversion and lateralization (P < .001). Lateral gaps in patellar reduction were also significantly larger than those in eversion and lateralization (P < .001). The mediolateral gap difference in patellar reduction was significantly greater at all flexion angles compared to those in eversion and lateralization (P < .001). In PS TKA, similar patterns were observed for medial gaps, lateral gaps, and mediolateral gap differences (P < .001).The ligament balancing with the patella everted or subluxed may lead to an overly tight medial gap and/or loose lateral gap in the knee with a closed arthrotomy, which has potential consequences for knee function in both CR and PS TKA designs. The results of this study highlight the importance of considering patellar position to ensure optimal soft-tissue balance and joint stability in TKA.