IS PATELLOFEMORAL OSTEOARTHRITIS A CONTRA-INDICATION TO UNICOMPARTMENTAL KNEE ARTHROPLASTY?

Abstract

Introduction: The indications for unicompartmental knee arthroplasty (UKA) remain controversial; in particular, the threshold of disease in the patellofemoral compartment is debated. Whilst some authorities ignore the condition of the patellofemoral joint, others consider pre-existing patellofemoral osteoarthritis (PFOA) a contraindication to UKA. The aim of this study was to determine the influence of PFOA on the outcome of medial UKA.

Methodology: This prospective study involved one hundred consecutive patients who had undergone cemented medial Oxford UKA (phase 3), via a minimally invasive approach, at least one year previously. Patients were divided into two groups according to the presence or absence of full thickness cartilage loss (FTCL) on the patella or trochlea at operation. Outcome was evaluated with the Knee Society Score (AKSS) and the Oxford Knee Score (OKS, maximum 48). Groups were compared for differences in knee score and intra-operative cartilage status of PFJ using a one way ANOVA. Repeat analysis was performed using the presence of anterior knee pain (AKP) as the group defining variable.

Results: There were 35 patients with FTCL and 65 without. Both groups were well matched for age, gender and activity levels. No significant difference in post operative knee scores existed between groups for the pre-operative presence of FTCL (OKS = 40 in both groups). Similar, non significant, results were found when the pre-operative presence of AKP was used as a group defining factor (OKS 40 Vs 39). The study was sufficiently powered to avoid type II error.

Conclusion: Intra-operative evidence of PFOA in patients with medial compartment osteoarthritis does not prejudice the outcome of UKA at one year. Moreover, the inclusion of patients with symptomatic AKP (with or without concurrent PFOA) also appears not to influence the outcome after UKA.