Impact of the Femoral Pin Tracker on Soft-Tissue Tension in Robotic-Assisted Total Knee Arthroplasty

BACKGROUND: The femoral pin tracker in robotic-assisted total knee arthroplasty (TKA) can be placed intraincisionally or extraincisionally. The purpose of our study was to determine the impact of these placement methods on soft-tissue tension in the knee joint. METHODS: A total of 132 patients undergoing robotic-assisted TKA were prospectively enrolled; of those, 80 were randomized to receive an intraincisional or extraincisional femoral pin tracker during surgery. Soft-tissue tension in the medial and lateral compartments of the knee joint was measured using a sensor before and after the removal of the pin tracker. Measurements were performed at 10°, 45°, 90°, and 120° of knee flexion. Changes in knee joint soft-tissue tension from before to after the removal of the pin tracker were compared between the 2 groups. RESULTS: Our trial included 80 patients (mean age, 66.98 ± 38.48 years; 24% male; 100% Han Chinese). The intraincisional group demonstrated significantly greater changes in soft-tissue tension in the medial compartment of the knee at 10° (p < 0.001), 45° (p = 0.028), and 90° (p = 0.046) of knee flexion compared with the extraincisional group. No significant between-group differences were found in the changes in tension in the medial compartment at 120° of knee flexion (p > 0.05) or in the lateral compartment at any angle (p > 0.05). CONCLUSIONS: Intraincisional placement of the femoral pin tracker may influence soft-tissue tension in the medial compartment of the knee. Surgeons should be aware of these differences when performing soft-tissue balancing before the removal of the femoral pin tracker. LEVEL OF EVIDENCE: Therapeutic Level I . See Instructions for Authors for a complete description of levels of evidence.