Pinless navigation in total knee arthroplasty: Navigation reduced by the maximum?

Purpose Restoring a neutral mechanical axis in total knee arthroplasty (TKA) (within +/- 3 degrees of varus/valgus) is associated with superior functional outcome and reduced early implant failure. Using conventional alignment jigs results in malalignment in >20 % of cases. In this study, we investigated the reduction of outliers within the threshold of +/- 3 degrees of leg alignment using a pinless navigation system in comparison with conventional alignment jigs investigated. Methods In this randomised prospective study, 80 patients were randomly assigned/allocated to the pinless or conventional control group. After surgery, the two groups were compared regarding outliers>+/- 3 degrees by means of hip-knee-ankle angle (HKA), mechanical medial proximal tibia angle (mMPTA), mechanical lateral distal femoral angle (mLDFA) and duration of surgery. Student's unpaired t test was used for quantitative variables, Fisher's exact test compared groups (pinless vs. control) and a two-sided p value of <= 0.05 was considered statistically significant. Results In the pinless group, outliers regarding HKA and mLDFA>+/- 3 degrees was significantly reduced (p = 0.025 and p = 0.002 respectively). In the pinless group, the surgery duration was significantly longer (75.6 vs. 64.5 minutes, p < 0.001). Conclusion Pinless navigation is effective in reducing outliers>+/- 3 degrees regarding HKA without risking pin-related complications, such as fractures, infections or breaking screws. However, not all tools for conventional navigation in TKA, such as real-time measurements of the tibiofemoral axis and gap balancing, are available.