Common adjustments made in robotic total knee arthroplasty to achieve functional alignment and minimize soft tissue...

The accuracy and precision of robotics in total knee arthroplasty (TKA) allows for intentional adjustments in bone cuts to accommodate soft tissue sleeve characteristics. This study evaluated common femoral and tibial resection adjustments in robotic-assisted TKA (rTKA) categorized by preoperative deformity, using an imageless, semi-autonomous robotic system.

In this retrospective study, 292 patients underwent rTKA between October 2019 and December 2023 at a single institution by two fellowship-trained surgeons. Functional alignment was attained by registering soft tissue gaps prior to bony resection and adjusting the bony cuts to partially or completely accommodate these gaps. Patients were categorized by preoperative Hip-Knee-Ankle (HKA) angles. Chi-square tests and ANOVA models compared adjustments across preoperative alignment groups.

The cohort included 167 (57.2 %) females, an average age 66.6 ± 9.0 years and average BMI of 30.6 ± 5.6 kg/m2. Preoperative alignment was 54.8 % varus, 22.9 % neutral and 22.3 % valgus. Common adjustments in varus and neutral knees involved the addition of varus (relative to neutral mechanical alignment) to the femoral cut (85 %) and/or tibial cut (85 %) to accommodate the often looser lateral compartment. In valgus knees, the most common adjustment included the addition of valgus to the femoral cut (63 %), but no change to the mechanically neutral tibial cut (66 %) to accommodate the often looser medial compartment. To balance the flexion gap, external rotation (relative to the posterior condylar axis) was added to all knees with a mean 5.3° (range: 1.9-10°) to accommodate the looser lateral compartment in flexion.

This study outlines the common femoral and tibial resection adjustments made from default neutral mechanical alignment based on pre-operative HKA. The range of bony resection adjustments highlights the ability of robotics to accommodate variations in ligamentous integrity and preoperative alignment findings. Further research is needed to determine if these adjustments result in improved outcomes or longevity.