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° valgus and the average alignment of the Repicci prosthesis was 4.5° 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.