Navigated versus conventionally instrumented total knee arthroplasty techniques: No difference in functional alignment or balance

Purpose: Much debate exists about the superiority of navigated versus conventional instrumentation for achieving optimal balance and alignment during total knee arthroplasty (TKA). Recent registry data indicate no long-term survivorship benefit for TKAs performed using technology assistance, despite the added resource and financial costs. However, outcome comparisons are confounded by varying surgeon techniques and targets for ideal balance and alignment. This study aimed to investigate alignment or balance outcome differences between navigated and conventionally instrumented TKAs performed using an identical operative sequence and alignment strategy.

Methods: Fifty navigated and 50 conventionally instrumented primary TKAs, using an identical inverse kinematic alignment strategy, were included. Navigation equipment was used intraoperatively to 'post-cut' record the conventionally instrumented TKAs. Intraoperative balance, range, and alignment; and post-operative radiographic accuracy for restoration of constitutional alignment were compared.

Results: Forty-nine navigated and 49 conventionally instrumented TKAs were compared (n = 2 excluded due to inadequate radiographs). No preoperative demographic or deformity severity differences existed. No intraoperative balance, range or alignment difference existed. Neither technique was more accurate for restoration of constitutional alignment.

Conclusion: Whilst large registry data may be confounded by uncaptured variables such as surgeon balancing techniques or surgeon alignment strategy preferences, this study found no alignment or balance differences between navigated versus conventionally instrumented TKA techniques for a surgeon and technique-controlled study. Although the increased resources necessary for technology assistance are not justified by this study, further studies may identify significance using larger samples or comparison of alternative outcomes.

Level of evidence: Level II.