Establishing the Minimally Important Difference for the KOOS–Joint Replacement and PROMIS Global–10 in Patients After Total Knee Arthroplasty
Tyler Spiering, Andrew Firth, Christos Mousoulis, Brian R. Hallstrom, Joel Gagnier
Abstract
Background: Despite the overall prevalence and success of total knee arthroplasty (TKA), a significant portion of patients are dissatisfied with their outcomes. Purpose: To assess the responsiveness and determine the minimally important difference (MID) of 2 patient-reported outcome measures (PROMs)—the Knee injury and Osteoarthritis Outcome Score–Joint Replacement (KOOS-JR) and the Patient-Reported Outcomes Measurement Information System Global–10 (PROMIS 10)—in patients after TKA. Study Design: Cohort study (diagnosis); Level of evidence, 3. Methods: Included were patients who underwent TKA from August 2015 through August 2019 and completed baseline and postoperative KOOS-JR and PROMIS 10 surveys. The PROMIS 10 consists of 2 domains: physical health and mental health. Estimates for the reliable change index (RCI) and MID, using anchor-based and distribution-based methods, were calculated for each PROM. Regression modeling was used to determine whether patient and clinical factors predicted MID thresholds or MID achievement. Results: A total of 1315 patients were included. Distribution-based MIDs, calculated using various methods from baseline scores, ranged from 19.3 to 31 for the KOOS-JR, and the RCI was 4.38. Of these patients, 293 (22.3%) demonstrated small or moderate improvement, and this cohort was included in the calculation of anchor-based MIDs. The anchor-based MIDs were 16.9 and 24.3 at 3-month and 1-year follow-up, respectively, and 66% of patients achieved the MID at 12 months. Higher preoperative PROM score, male sex, non-White race, and current smoker status were predictive of failing to achieve the anchor-based MID for KOOS-JR at 1 year postoperatively ( P < .05). Higher preoperative PROM score and any 90-day adverse event predicted lower thresholds of important change in anchor-based MIDs. Higher baseline PROM scores, younger age, male sex, non-White ethnicity, higher American Society of Anesthesiologists classification, preoperative narcotics use, not smoking, and longer hospital stay were all associated with lower odds of achieving the MID on the KOOS-JR or either of the PROMIS 10 subscales. Conclusion: The study results demonstrated relevant values for interpretation of the KOOS-JR and PROMIS 10. While patient demographics did not accurately predict which patients would achieve the MID, some potential factors predicting successful patient-reported outcomes after TKA were identified.