Fixed lateral unicompartmental knee replacement is a reliable treatment for lateral compartment osteoarthritis after mobile‐bearing medial unicompartmental replacement

Abstract

AbstractPurposeLateral osteoarthritis following medial unicompartmental knee replacement (UKR) is usually treated with total knee replacement, however, lateral UKR is a less invasive option that preserves a well‐functioning medial UKR. This study aimed to determine the 5‐year outcome of the cemented Fixed Lateral Oxford UKR (FLO) when used for the treatment of severe lateral disease after medial Oxford unicompartmental knee replacement.MethodsForty‐four knees with lateral bone‐on‐bone osteoarthritis (n = 43) and avascular necrosis (n = 1) treated with the FLO following medial Oxford UKR were followed up prospectively. The Oxford Knee Score (OKS) and Tegner Activity Score (TAS) were collected pre‐ and post‐operatively. Life‐table analysis was used to determine survival rates.ResultsThe mean patient age at the time of FLO surgery was 74.4 years with a mean time of 12.1 years between the primary medial UKR and the conversion to a bi‐UKR with a FLO. Mean follow‐up of the FLO was 3.5 years. After FLO no intra‐operative or medical complications, re‐admissions, or mortality occurred. There was one reoperation in which a bearing was exchanged for a medial bearing dislocation. There were no revisions of the FLO, so the FLO survival rate at 5 years was 100% (24 at risk). The mean pre‐operative OKS was 22, which significantly (p < 0.0001) improved to a mean of 42, 42, and 40 at 1, 2, and 5 years, respectively. The median TAS had a non‐significant improvement from 2.5 (Range 0–8) pre‐operatively to 2 (Range 1–6) at 5 years postoperatively.ConclusionThe FLO is a reliable treatment for lateral osteoarthritis following medial UKR. At 5 years there was a 100% survival of the FLO with a mean OKS of 40.Level of evidenceIV, Prospective Case Series.