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BACKGROUND: The benefits and risks of a single-stage medial UKA remains a subject of debate because of the theoretically higher risk of complications and specifically blood loss. The aim of this study was to evaluate the perioperative blood loss, risks and the functional results of single-stage bilateral medial Oxford Unicompartmental Knee Arthroplasty (OUKA) compared to a standard unilateral medial OUKA procedure (control group). HYPOTHESIS: The blood loss observed during bilateral single-stage medial Oxford UKA is not different from that of the control group. METHODS: In this case-control prospective study, fifty patients (100 knees) who underwent single-stage bilateral medial OUKA (study group) were compared to a hundred patients (100 knees) with unilateral medial OUKA (control group), performed by the same surgeon. The real blood loss (in mL of hematocrit at 100%), incidence of blood transfusions, and complication rates were compared. Clinical results were assessed at 6 month and at a two-year minimum follow-up (FU) using IKS, KOOS and OKS scores, in addition to a satisfaction questionnaire. RESULTS: Groups were deemed comparable. Concerning blood loss, no significant difference was observed compared to the control group (465mL±225 vs. 396±190; p=0.07). No difference was found, either, between groups regarding the complication rates (p=0.36), nor the clinical results (p=0.61) and patient satisfaction (p=0.23) at last FU. CONCLUSION: Single-stage bilateral procedure does not cause increased blood loss compared with controls. Moreover, clinical results were deemed good and excellent in spite of a slightly greater complication rate than those found in the literature but similar to controls. LEVEL OF EVIDENCE: Case-control study, level III.

Original publication




Journal article


Orthop traumatol surg res

Publication Date





943 - 947


Blood loss, Complications, Functional results, Knee, Single-stage bilateral, Unicompartmental knee arthroplasty