The results of Oxford unicompartmental knee arthroplasty in the United States: a mean ten-year survival analysis

Abstract

Aims: Approved by the Food and Drug Administration in 2004, the Phase III Oxford Medial Partial Knee is used to treat anteromedial osteoarthritis (AMOA) in patients with an intact anterior cruciate ligament. This unicompartmental knee arthroplasty (UKA) is relatively new in the United States, and therefore long-term American results are lacking.

Patients and methods: This is a single surgeon, retrospective study based on prospectively collected data, analysing a consecutive series of primary UKAs using the Phase III mobile-bearing Oxford Knee and Phase III instrumentation. Between July 2004 and December 2006, the senior author (RHE) carried out a medial UKA in 173 patients (213 knees) for anteromedial osteoarthritis or avascular necrosis (AVN). A total of 95 patients were men and 78 were women. Their mean age at surgery was 67 years (38 to 89) and mean body mass index 29.87 kg/m2 (17 to 62). The mean follow-up was ten years (4 to 11).

Results: Survivorship of the Oxford UKA at ten years was 88%, using life table analysis. Implant survivorship at ten years was 95%. The most common cause for revision was the progression of osteoarthritis in the lateral compartment. The mean knee score element of the American Knee Society Score (AKSS) was 50 pre-operatively and increased to 93 post-operatively. The mean AKSS function score was 56 pre-operatively rising to 78 post-operatively CONCLUSION: This ten-year follow-up study of the Oxford UKA undertaken in the United States shows good survivorship and excellent function in a wide selection of patients with AMOA and AVN. Cite this article: Bone Joint J 2016;98-B(10 Suppl B):34-40.

Keywords: 10-year Survivorship; Oxford Partial Knee System; Unicompartmental Knee Arthroplasty.

Fig. 1

Unicompartmental knee arthroplasty (UKA) survivorship at ten years - survival curve showing survival of the minimally invasive Oxford phase III UKA with all revisions as the end point.

Fig. 2

Implant survivorship at 10 years - survival curve showing survival of the minimally Oxford phase III unicompartmental knee arthroplasty with non-implant related revisions as the endpoint.

Fig. 3

American Knee Society Score (AKSS) pre- and post-operative scores - clinical outcomes (mean,sd error bars). AKSS Knee and function scores displayed. The mean AKSS follow-up for scores is 8 years (0.5 to 11).

Fig. 4

Bearing thickness implanted versus revised: bar chart demonstrating total number of bearings implanted and revised, for thin (3 mm to 4 mm) and thick (5 mm to 7 mm) bearings.