Comparison of Patellar Position After Mobile-Bearing and Fixed-Bearing TKA: A Prospective Randomized Study

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Abstract

Objectives: Total knee arthroplasty (TKA) is the treatment of choice for severe knee osteoarthritis. While many studies compare mobile- and fixed-bearing designs, data on patellar position between these systems remains insufficient. This study aimed to measure and compare patellar position in mobile- and fixed-bearing TKA systems. Methods: This prospective randomized study assessed 160 TKA patients, with 79 receiving a mobile-bearing tibial insert and 81 receiving a fixed-bearing system, between 2007 and 2009. The mean ages were 72 and 70 years, with a mean follow-up of 7.4 years (range 5-11 years). Both groups were comparable pre- and post-operatively using the International Knee Society (IKS) score. Patellar tilt and translation were measured using the technique described by Gomes et al. Results: There were no significant differences between the two groups in the Knee Society knee scores (94 vs 92; p=0.45), pain score (45.8 vs 45.8; p=0.97), function scores (83.2 vs 83.9; p=0.78), or maximum knee flexion (116 vs 112; p=0.07) at the 7-year follow-up. Patellar translation and tilt were also not statistically different between the mobile-bearing and fixed-bearing TKAs. However, a significant difference was found in the subgroup with patellar translation greater than 5mm (OR=2.3; p=0.048) in favor of the mobile-bearing design, although this had no impact on clinical outcomes. Conclusion: No advantages were found for mobile-bearing TKA regarding pain, function, maximum knee flexion, or radiographic outcomes, such as patellar tilt or translation. Longer-term follow-up is required to determine any potential benefits of mobile-bearing over fixed-bearing TKA.