Robotic arm-assisted versus conventional jig-based unicompartmental knee arthroplasty achieves better soft-tissue balance

Aims: We developed a novel unicompartmental pressure sensor to measure intraoperative medial compartment pressureduring robotic arm-assisted unicompartmental knee arthroplasty (UKA) and conventional jig-based UKA in order to assess the effect and impact of soft-tissue balance. Methods: This retrospective study evaluated 80 patients who underwent medial compartment UKA at our institution between November 2022 and June 2023, including 40 patients in conventional jig-based (mobile bearing) UKA and 40 patients in robotic arm-assisted (fixed bearing) UKA. After intraoperative soft-tissue balancing, the medial compartment pressure at 10°, 45°, and 90° of knee flexion was measured using a new unicompartmental pressure sensor. The knee range of motion (ROM), Numerical Rating Scale, and American Knee Society scores were recorded at three months and one year of follow-up. Results: Conventional jig-based UKA did not achieve consistent medial compartment pressures at 10°, 45°, and 90° of knee flexion (p < 0.001), whereas robotic arm-assisted UKA achieved more balanced pressures at these angles (p-values between 10° vs 45°, 10° vs 90°, and 45° vs 90° were 0.132, 0.378, and > 0.999, respectively). In addition, robotic arm-assisted UKA showed better outcome scores and ROM at three months, but no significant clinical differences at the one-year follow-up. Conclusion: Intraoperative pressure measurements using the novel unicompartmental pressure sensor showed that robotic arm-assisted UKA was able to achieve more consistent pressure in the medial compartment than conventional jig-based UKA, which may improve early postoperative rehabilitation.