TOTAL AND UNICONDYLAR KNEE ARTHROPLASTY PRE-OPERATIVE OXFORD KNEE SCORING - DO THE POPULATIONS DIFFER?

Abstract

Background: In a recent publication from the National Joint Registry it was suggested that prosthesis type influenced patient satisfaction at one year following knee arthroplasty. In this report Unicondylar Replacement (UKR) was associated with lower levels of patient satisfaction when compared to cemented TKR. The unicondylar group did however have a significantly lower Oxford Knee Score (OKS) than the TKR group and this occurred irrespective of patient age.

A common perception is that UKR is only offered to patients with lesser disease, with a decreased clinical profile. This may explain their higher levels of dissatisfaction as the overall change in their OKS from pre to post operation would be relatively smaller than for TKR.

Aim: We hypothesised that patients listed for UKR have less severe disease and therefore a lower preoperative OKS when compared to TKR.

Methods: After sample size calculation we retrospectively analysed 76 patients who underwent either UKR or TKR under the care of a single surgeon. OKS was recorded at a dedicated pre-assessment clinic. The decision to offer UKR was based on clinical and radiological criteria as outlined by the Oxford group.

Results: There were 38 patients in either group. The mean pre-operative OKS was 39.5 (26–56, SD 7.6) in the UKR group and 41.6 (31–51, SD 5.7) in the TKR group. There was no statistical difference between these two groups (p=0.18).

Discussion: Patients listed for knee replacement have significant pain and functional impairment. In our population those suitable for UKR have similarly severe symptoms to those who do not meet the criteria for UKR and are only eligible for TKR. It remains unclear why patients undergoing UKR should be less satisfied when they have better post operative patient reported outcome scores. It emphasizes the need for careful patient selection and counselling in patient undergoing UKR.