Mobile Versus Fixed Bearing Medial Unicompartmental Knee Arthroplasty: A Series of 375 Patients

We sought to compare outcomes, complications and survival between mobile and fixed bearing medial unicompartmental knee arthroplasty (UKA) in a large multi-surgeon group. Methods: Medical records of patients who underwent a medial UKA were queried between March 2003 and August 2012. Variables investigated included final range of motion (ROM), type of complication, and overall survivorship.  Results: 375 medial UKAs were analyzed (308 mobile bearing and 67 fixed bearing). Average time to follow-up was 47 months. Final ROM was comparable (mobile: 1-122°, fixed: 1-120°, p = 0.34). Complications occurred in 20/308 (6.6%) mobile bearing UKA and 5/67 (7.5%) fixed bearing UKA (p = 0.77). The most common complications in mobile bearing implants were progression of lateral compartment disease and component loosening. The complications in fixed bearing implants were arthrofibrosis and tibial plateau fracture. Overall survivorship differed, but not significantly (mobile: 94.8%, fixed: 96.9%, p = 0.44).  Discussion: In this largest reported cohort series comparing mobile versus fixed bearing UKA, we found no significant difference in final clinical knee range of motion, rates of complications, and survivorship between the two bearing types.