Defining Minimal Clinically Important Difference Thresholds for Pediatric Knee Surgeries.

Background: The minimal clinically important difference (MCID) has been established for adult questionnaires administered after pediatric anterior cruciate ligament reconstruction (ACLR) and medial patellofemoral ligament reconstruction (MPFLR), but the MCID remains unquantified in pediatric-specific patient-reported outcome (PRO) instruments. Purpose: To establish MCIDs for the Hospital for Special Surgery Pediatric Functional Activity Brief Scale (HSS Pedi-FABS), Pediatric International Knee Documentation Committee (Pedi-IKDC), and pediatric and parent-proxy Patient-Reported Outcomes Measurement Information System (PROMIS) pain interference (PI), mobility, and physical activity scores in pediatric patients who underwent ACLR and MPFLR. Study Design: Cohort study; Level of evidence, 3. Methods: The medical records of patients <18 years of age who underwent ACLR or MPFLR with 1 of 2 pediatric orthopaedic surgeons between 2016 and 2023 were retrospectively reviewed. Patient demographic and clinical factors were collected. Preoperative HSS Pedi-FABS, Pedi-IKDC, and pediatric and parent-proxy PROMIS pain interference (PI), physical activity, and mobility questionnaire scores were collected. The MCID was defined as one-half the standard deviation of preoperative scores. The MCIDs were calculated for patients undergoing ACLR and MPFLR. Results: In the ACLR group (505 patients; mean age, 14.5 ± 2.0 years), the MCIDs were established for the HSS Pedi-FABS (-5.0); Pedi-IKDC (8.7); pediatric PROMIS PI (-5.2), mobility (2.2), and physical activity (5.6); and parent-proxy PROMIS PI (-4.3), mobility (4.3), and physical activity (5.0) questionnaires. In the MPFLR group (253 patients; mean age, 14.4 ± 2.1 years), the MCIDs were established for the HSS Pedi-FABS (-5.1); Pedi-IKDC (9.1); pediatric PROMIS PI (-5.7), mobility (4.9), and physical activity (5.6); and parent-proxy PROMIS PI (-4.3), mobility (4.5), and physical activity (5.9) questionnaires. Negative MCIDs were reported for activity and pain scores to indicate MCID thresholds for decreased postoperative pain (i.e., pain improvement) and activity levels (i.e., decreased activity levels compared to healthiest and most active condition, absence of full recovery). Conclusion: This study establishes novel MCIDs for the HSS Pedi-FABS, Pedi-IKDC, and pediatric and parent-proxy PROMIS PI, physical activity, and mobility questionnaires in pediatric patients undergoing ACLR and MPFLR.