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

ABSTRACT

PURPOSE: Restoring a neutral mechanical axis in total knee arthroplasty (TKA) (within ±3° 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° 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° 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° 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° 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.