Results of the Oxford Phase 3 mobile bearing medial unicompartmental knee arthroplasty from an independent center: 467 knees at a mean 6-year follow-up: analysis of predictors of failure.

A retrospective review of 467 Oxford UKAs was performed in 387 patients. Thirty-eight knees (8.1%) were revised to TKA at a mean of 49 months, most commonly for lateral compartment OA (47%). The 5-year cumulative survival using revision to TKA was 98.5%. Revisions required short stems in 26% and augments in 21% of cases. The mobile bearing dislocation rate was 0.64%. Correction of ≥3-5° from the preoperative alignment in a valgus direction was predictive of revision to TKA (P<.0001). Multivariate analysis revealed female gender (P=.002) also was associated with an increased risk of revision. Careful attention to the degree of mechanical axis correction with an overall maintained varus alignment may reduce revision rates for mobile bearing UKA.