Comparison of Time and Rate of Achieving Minimal Clinically Important Difference: Robotic Versus Manual Unicompartmental Knee Arthroplasty

Abstract

Background: Robotics in unicompartmental knee arthroplasty (UKA) continues to increase with the ever-growing demand to use technology in the surgical setting. However, no studies have used minimal clinically important difference (MCID) to compare patient-reported outcome measures (PROMs) between robotic UKA (rUKA) and manual UKA (mUKA). This study aimed to compare the rate of achieving MCID for improvement (MCID-I) and worsening (MCID-W) and the time to achieving MCID. Methods: We conducted a retrospective analysis of robotic and manual UKAs performed between 2016 and 2022. Preoperative and postoperative Patient-Reported Outcomes Measurement Information System (PROMIS) Global Physical, PROMIS Physical Function Short-Form 10a (PF-10a), and Knee Injury and Osteoarthritis Outcome Score-Physical Function Short-Form (KOOS-PS) scores were collected. Patients were stratified on reaching MCID-I, MCID-W, or “no notable change” (score between MCID-W and MCID-I). Survival curves with and without interval censoring were used to assess the time to achieving the MCID. Log-rank and weighted log-rank tests were used to compare groups. Results: A total of 256 UKAs (64 robotic and 192 manual) were analyzed. No differences were observed in the proportion of patients achieving MCID-I or MCID-W across all three PROMs. Similarly, median time to achieving MCID showed no significant differences between rUKA and mUKA for PROMIS Global Physical (3.3 versus 4.9 months, P = 0.44), PROMIS PF-10a (7.7 versus 8.3 months, P = 0.93), and KOOS-PS (3.0 versus 6.0 months, P = 0.055) scores, both with and without interval censoring. Discussion: This study indicates that rUKA and mUKA exhibit comparable rates of achieving MCID-I and MCID-W, along with similar median time to reach MCID. These findings offer valuable patient-centric insights into the effectiveness of rUKA. Additional studies evaluating the long-term outcomes of rUKA are needed to determine its long-term advantages. Level of evidence: Level III, retrospective comparative study.