Unicompartmental knee arthroplasties revised to total knee arthroplasties compared with primary total knee arthroplasties.

We studied the technical operative features and the subjective outcomes of 63 patients requiring a revision to a total knee arthroplasty (TKA) for failed Oxford medial unicompartmental knee arthroplasty. We compared this revision study group to a contemporary control cohort of 126 patients who underwent primary TKAs. The 2 groups from the same institution had a minimum follow-up of 2 years and were retrospectively matched 1:2 for age, sex, body mass index, and follow-up time. Length of stay and hemoglobin level drop were similar. Technically, the revision group required larger polyethylene inserts (P < .001) and longer tourniquet times (P < .001) with 15 of these patients needing augments, grafts, and/or stems. Subjectively, the revision group's mean total Western Ontario and McMaster Universities Arthritis Index score was 25.8 ± 20.2, thus less satisfactory compared with the control group (19.8 ± 15.3) at a mean follow-up of 3.1 years (P = .03). A revision unicompartmental knee arthroplasty to TKA is technically more difficult and functionally less satisfactory at last follow-up when compared with a primary TKA.