TECHNICAL PITFALLS WHILE IMPLANTING THE OXFORD MEDIAL CEMENTED UNICOMPARTMENTAL KNEE ARTHROPLASTY (OXF UKA)—LESSONS LEARNT OVER 8 YEARS.

Abstract

The minimally invasive technique recommended by the designers in the implantation of the OXF UKA make for a demanding procedure: most recorded failures are of a technical nature and occur within the first 2-years of implantation. Also, data from the Swedish and NZ National Joint Registries (NJR) show clearly that revision rates and surgeon experience are inversely related.

To present some technical points, using illustrative cases, where implantation has been associated with suboptimal outcome, or has lead to re-operation. To offer solutions for these potential problems

In 2004, data from the NZ NJR allowed analysis of all failures of OXF UKA leading to revision. The case notes and x-rays (where available) were studied (Hartnett et al, NZOA ASM, 2004). Clinical records of personal cases performed over 8 years up till July 2008 have also been studied and provide the illustrative cases.

On the tibial side, mismatch between the length of the keel on the tibial component and the bony slot created for it can cause the tibial component to be too posteriorally-sited. Also, if too much cement is used, posterior protrusion of cement may be difficult to detect at operation. The combination of these two may cause symptoms postero-medially. Ways of preventing these problems are outlined.

On the femoral side, NZJR records that aseptic loosening of the femoral component is a prominent cause of failure of OXF UKA. A number of techniques to improve cement intrusion can be implemented and are outlined. A case study of the only such encountered describes the possibility that the femoral intramedullary guide rod can inadvertently be driven into the femoral canal by knee motion during operation: this remained undetected until shown on the x-ray taken after operation.

Simple modifications of technique can minimise the chance of suboptimal outcome after OXF UKA surgery.