Mobile-bearing unicompartmental knee replacements (UKRs) with a flat tibial plateau have not performed well in the lateral compartment, owing to a high dislocation rate. This led to the development of the Domed Lateral Oxford UKR (Domed OUKR) with a biconcave bearing. The aim of this study was to assess the survival and clinical outcomes of the Domed OUKR in a large patient cohort in the medium term.

We prospectively evaluated 265 consecutive knees with isolated disease of the lateral compartment and a mean age at surgery of 64 years (32 to 90). At a mean follow-up of four years (sd 2.2, (0.5 to 8.3)) the mean Oxford knee score was 40 out of 48 (sd 7.4). A total of 12 knees (4.5%) had re-operations, of which four (1.5%) were for dislocation. All dislocations occurred in the first two years. Two (0.8%) were secondary to significant trauma that resulted in ruptured ligaments, and two (0.8%) were spontaneous. In four patients (1.5%) the UKR was converted to a primary TKR. Survival at eight years, with failure defined as any revision, was 92.1% (95% confidence interval 81.3 to 100).

The Domed Lateral OUKR gives good clinical outcomes, low re-operation and revision rates and a low dislocation rate in patients with isolated lateral compartmental disease, in the hands of the designer surgeons.

Cite this article: Bone Joint J 2014;96-B:59–64.

The Oxford unicompartmental knee replacement (UKR) is an established treatment option in the management of symptomatic end-stage medial compartmental osteoarthritis (MCOA), which works well in the young and active patient. However, previous studies have shown that it is reliable only in the presence of a functionally intact anterior cruciate ligament (ACL). This review reports the outcomes, at a mean of five years and a maximum of ten years, of 52 consecutive patients with a mean age of 51 years (36 to 57) who underwent staged or simultaneous ACL reconstruction and Oxford UKR. At the last follow-up (with one patient lost to follow-up), the mean Oxford knee score was 41 (sd 6.3; 17 to 48). Two patients required conversion to TKR: one for progression of lateral compartment osteoarthritis and one for infection. Implant survival at five years was 93% (95% CI 83 to 100). All but one patient reported being satisfied with the procedure. The outcome was not significantly influenced by age, gender, femoral or tibial tunnel placement, or whether the procedure was undertaken at one- or two-stages.

In summary, ACL reconstruction and Oxford UKR gives good results in patients with end-stage MCOA secondary to ACL deficiency.

STUDY PURPOSES

To evaluate the role of “top up” intra-articular local anaesthetic injection in patients who have had UKR.

Study Purposes: A retrospective study to assess patient’s height as a predictor for sizing the femoral component of the Phase 3 Oxford Unicompartmental Knee replacement.

Methods and Results: 118 patients post oxford uni-compartmental knee replacement were identified from the elective orthopaedic unit. Their post-operative radiographs were reviewed by 3 independent orthopaedic surgeons according to the Oxford Group criteria, measuring the femoral component fit. Patients were allocated to two cohorts: patients with ill-fitting prostheses and well fitting prosthesis.

Patient’s height and size of femoral component used at time of surgery was recorded. The results showed a positive correlation between the patient’s height and a well fitting femoral prosthesis.

Conclusions: Current templates with the Oxford Phase Three system may not provide accurate guide to the correct femoral prosthesis size for a patient. Recent studies have highlighted the wide range of magnifications used in computerised X-ray systems leading to variance with templating. Other studies have shown large inter-observer variability when sizing the femoral component. A variable as simple as patient height may offer a more accurate guide for choosing the size of the femoral component.

We have demonstrated that the height of a patient can be a used to guide and assist in the sizing of the femoral component of the Oxford uni-compartmental knee replacement. This study may also have implications for the sizing of other prostheses currently in use.