Comparison of two minimally invasive implantation instrument‐sets for total knee arthroplasty

AbstractSeveral choices of instrument systems are available for minimally invasive surgical approaches. There are reports that one alternative, the quadriceps sparing, side‐cutting instrumentation, results in diminished implantation accuracy. A total of 108 patients were randomized to undergo TKA either using side‐cutting implant instrumentation (Group A) or anterior–posterior mini‐incision instrumentation (Group B). All TKAs were operated on with a minimal invasive, mini‐midvastus surgical approach. 50% of the TKAs were performed with computer‐assistance in each cohort. The radiographic parameters, clinical outcomes and knee scores were evaluated preoperatively and 3 months postoperative. In Group B, we found significantly higher accuracy for the mechanical axis of the limb (range ±3°: Group A 54% versus Group B 89%, p = <0.001), medial proximal tibial angle (range ±3°: Group A 85% versus Group B 98%, p = <0.027) and tibial slope (range ±3°: Group A 59% versus Group B 85%, p = <0.007). The application of the navigation system could only significantly reduce outliers (accuracy >3°) in Group B. Clinical outcomes and knee scores were similar in both groups and were not influenced by computer‐assistance. Using the anterior–posterior, mini‐incision instruments for minimally invasive TKA will lead to higher implantation accuracy when compared to the quadriceps sparing side‐cutting instrumentation. The navigation technique could not compensate for shortcomings of the side‐cutting instrumentation. The clinical relevance of this study is that the quadriceps sparing side‐cutting instrumentation should not be used for TKA because of unacceptable reduced implantation accuracy.