Image-based robotics enhance precision and efficiency in lateral UKA: A comparative study of 135 UKAs.

Purpose: Robotic-assisted lateral unicompartmental knee arthroplasty (UKA) remains technically demanding due to the complex biomechanics of the lateral compartment. Image-based (IBRA) and imageless (ILRA) robotic systems have both demonstrated superior accuracy compared to conventional mechanical instrumentation, but have not yet been directly compared in lateral UKA. This study aimed to evaluate their respective accuracy and surgical efficiency.

Methods: This retrospective study included 135 patients who underwent lateral UKA using either IBRA or ILRA systems. Post-operative radiographic outcomes included hip-knee-ankle (HKA) alignment, posterior tibial slope (PTS) and joint line (JL) restoration. Surgical time was assessed as a secondary outcome. Target zones were HKA 180°-185°, PTS 2°-8° and JL ± 2 mm.

Results: IBRA showed higher rates of HKA inliers (94.9% vs. 78.9%, p = 0.011) and JL restoration (76.2% vs. 31.6%, p < 0.001) compared to ILRA. PTS accuracy was similar between groups (p = 0.30). Operative time was significantly shorter with IBRA (61.6 ± 13.5 vs. 81.9 ± 26.1 min, p < 0.001).

Conclusion: IBRA outperformed ILRA in terms of alignment accuracy and surgical duration. These findings support the added value of IBRA systems in lateral UKA.

Level of evidence: Level IV, retrospective case series study.