The twin peg Oxford knee - Medium term survivorship and surgical principles

A multicentre study of single peg Oxford knees reported failure associated with osteoarthritis progression, femoral component loosening, unexplained pain and meniscal bearing dislocation. Suboptimally positioned femoral components and intraoperative MCL damage could explain these problems. We hypothesised that modifying implantation technique to optimise femoral component positioning and MCL preservation, and introducing the twin peg Oxford knee would address these problems and improve longer term survival. Moreover, its better congruency in high flexion could reduce wear. This study aims to investigate this hypothesis by asking 1) Is the 98% survivorship up to nine years found in an earlier study sustained at longer term (up to 13 years)? 2) What are the remaining causes of failure?

We described our modified implantation technique. A cohort of all patients treated by the senior author using this modified technique and the Oxford twin peg cemented knee replacement between September 2003 and August 2013 was investigated. A survival analysis was performed and the causes of failure were analysed.

The cohort consisted of 468 patients with 554 medial cemented implants. In all, 16 implants were revised and the 12-year survivorship was 95%. Patients with extended indications had a lower survivorship than those with anteromedial osteoarthritis (10-year survival rate 78% vs 97%, p<0.001). There were no failures due to femoral loosening.

Using our surgical principles the cemented twin peg Oxford knee can result in good medium to long-term implant survival, comparable to those obtained by the originating centre for the single peg Oxford knee.