A comparison of highly instrumented and minimally instrumented unicompartmental knee prostheses

In this study, two specific implants are compared: the Oxford prosthesis, which uses a highly instrumented technique and was placed through a traditional arthrotomy; and the Repicci prosthesis, which uses a minimally instrumented technique and was placed with a minimally invasive surgical approach. The study looked specifically at limb alignment, because achieving appropriate alignment is correlated with the best long-term implant function and achieving alignment is a function of the implant instrumentation. The rationale of more instrumentation for a surgical technique is to add precision and reproducibility; less instrumentation requires less surgical exposure and therefore is more minimally invasive. The senior author presents his long-term experience with the Oxford implant (55 implants; average followup 10.4 years) and short-term experience with the Repicci implant (164 implants; average followup 1.3 years for the first 30 implants.). With available followup, the clinical results using both implants have been favorable. The average alignment of the Oxford prosthesis was 5.6 degrees valgus and the average alignment of the Repicci prosthesis was 4.5 degrees valgus. Side-to-side long-term comparison is not yet available, although the literature would suggest that both implants can have satisfactory long-term results. Specific implant selection probably is not as important as precise patient selection.