The MCID of the PROMIS physical function instrument for operatively treated tibial plateau fractures

Introduction: Understanding minimal clinically important differences (MCID) in patient reported outcome measurement are important in improving patient care. The purpose of this study was to determine the MCID of Patient-Reported Outcome Measurement System (PROMIS) Physical Function (PF) domain for patients who underwent operative fixation of a tibial plateau fracture. Methods: All patients with tibial plateau fractures that underwent operative fixation at a single level 1 trauma center were identified by Current Procedural Terminology codes. Patients without PROMIS PF scores or an anchor question at two-time points postoperatively were excluded. Anchor-based and distribution-based MCIDs were calculated. Results: The MCID for PROMIS PF scores was 4.85 in the distribution-based method and 3.93 (SD 14.01) in the anchor-based method. There was significantly more improvement in the score from the first postoperative score (<7 weeks) to the second postoperative time (<78 weeks) in the improvement group 10.95 (SD 9.95) compared to the no improvement group 7.02 (SD 9.87) in the anchor-based method (P < 0.001). The percentage of patients achieving MCID at 7 weeks, 3 months, 6 months, and 1 year were 37–42 %, 57–62 %, 80–84 %, and 95–87 %, respectively. Discussion: This study identified MCID values for PROMIS PF scores in the tibial plateau fracture population. Both MCID scores were similar, resulting in a reliable value for future studies and clinical decision-making. An MCID of 3.93 to 4.85 can be used as a clinical and investigative standard for patients with operative tibial plateau fractures.