Introduction. It is documented in the literature the very good results of lateral unicompartmental knee arthroplasty (UKA) when the standard accepted indications are followed. In our experience these indications can be extended to include post-traumatic osteoarthritis (OA) with malunion secondary to tibial plateau fracture. We report our results concerning 15 UKAs in these particular situations. Material and methods. From 1985 to 2009, we performed 15 lateral UKAs in 15 patients for post traumatic OA secondary to malunion following a tibial plateau fracture. 7 were female and 8 male. The mean age of the patients at the time of the index procedure was 45±17 years and the mean delay from initial trauma was 5.4 years. The average follow-up was 108 months (range 12–265 months). Results. Twelve patients (12 over 15) were satisfied or very satisfied (80%). At follow up 2 had undergone a second operation: 1 osteosynthesis for patellar fracture and 1 conversion to TKA for progression of OA (at 13.7 years after UKA) and one remained unsatisfied. No revision surgery was necessary for wear or infection. The average femoral-tibial alignment was 4° valgus (range −6° to 8°). The mean IKS knee score was 95.3 points and mean IKS function score was 92 points. Discussion. Our results in the medium term are excellent. They support that the selection criteria for UKA can be extended to include these indications. A longer follow up is required before they can be routinely included in the conventional selection criteria for UKA

Introduction

Radiolucencies beneath the tibial component are well recognized in knee arthroplasty; the aetiology and significance are poorly understood. Non-progressive narrow radiolucencies with a sclerotic margin are thought not to be indicative of loosening. Factors which decrease the incidence of radiolucencies include cementless fixation and the use of pulse lavage. Leg/component alignment or BMI do not influence radiolucency. We are not aware of any studies that have looked at the effect of load type on radiolucency.

The Oxford domed lateral tibial component was introduced to decrease the bearing dislocation rate that was unacceptably high with the flat tibial tray. However, the introduction of the domed tibial component alters the forces transmitted through the implant-cement-bone interface. As the Oxford UKR uses a fully congruent mobile bearing, the forces transmitted through the interface with a flat tray are compressive, except for the effect of friction. However, with the domed tibial component shear forces are introduced. The aim of this study was to assess the prevalence of radiolucency beneath the previous flat design and the new domed tibial tray.