The Oxford Medial Partial Knee Replacement. The rationale for a femur first technique

Background The Oxford Medial Partial Knee Replacement (PKR) has been in clinical use for more than 20 years. The current surgical technique requires a number of judgements to be made, and even in the most experienced hands surgery can be challenging. We present an alternative surgical technique, which we believe addresses the unpredictability of the current method. The technique is based on precise femoral positioning prior to tibial resection. Method A prospective series of 125 Oxford Medial PKRs was performed using this new technique and a radiographical analysis was performed. We used meniscal thickness, meniscal position and femoral position as measures of reproducibility of the procedure. Results Variability in meniscal thickness has been minimised with a 3 mm meniscal bearing used in 21 knees (15%), 4 mm (the target thickness) in 73 knees (59%) and 5 mm in 30 knees (24%). The mean meniscal position relative to the tibial tray upright was 2 mm (SD 1 mm). Femoral component position relative to the tibial tray, which defines the excursion of the meniscus was also assessed. Mean coronal plane alignment was 2° of valgus (SD 2.8). Mean flexion/extension was 3.8° (SD 3.1). The mean rotation was 10° internal (SD 5°). Conclusion We believe this new technique makes this procedure more reproducible, and should be considered as a viable alternative to the current recommended technique. It may be a better technique for those surgeons who are relatively inexperienced with this prosthesis.