The Clinically Important Difference and Patient Acceptable Symptomatic State for Commonly Used Patient-Reported Outcomes After Knee Cartilage Repair

Abstract

Background: In patients undergoing cartilage restoration of the knee, limited information is available regarding clinically important difference (CID) and Patient Acceptable Symptomatic State (PASS) estimates for commonly used patient-reported outcome measures (PROMs).

Purpose: The objective of this study was to determine the CID and PASS in the population with knee cartilage restoration for the Knee injury and Osteoarthritis Outcome Score (KOOS), the International Knee Documentation Committee Subjective Knee Form (IKDC) score, and the Lysholm score.

Study design: Cohort study (Diagnosis); Level of evidence, 2.

Methods: Between 2012 and 2017, patients who underwent a cartilage restoration procedure were prospectively enrolled. Patients completed the KOOS, IKDC, and Lysholm, all of which were scored from 0 to 100, and completed relevant anchor questions at baseline and 1 year postoperatively. Receiver operating characteristic curve analyses were conducted to determine CID and PASS cutoff points. Multivariable regression analyses were performed to determine the effect of age, sex, and baseline score on likelihood of achieving CID and PASS.

Results: Of the 113 patients enrolled, 53 (47%) were male, and the mean age was 36 years. The CID values for the PROMs were 10.7 for KOOS Symptoms, 8.3 for KOOS Pain, 8.8 for KOOS Activities of Daily Living (ADL), 30.0 for KOOS Sports and Recreation, 18.8 for KOOS Quality of Life (QOL), 9.2 for IKDC, and 13.0 for Lysholm. The PASS values were 71.5 for KOOS Symptoms, 72.2 for KOOS Pain, 86.8 for KOOS ADL, 43.8 for KOOS Sports and Recreation, 50.0 for KOOS QOL, 62.1 for IKDC, and 70.0 for Lysholm. Patients with higher baseline scores were more likely to achieve PASS for the IKDC (odds ratio, 2.28; P = .03). Baseline score did not have an effect on the likelihood of achieving CID. Younger age was an independent predictor of achieving PASS and CID across all outcomes (P < .05), but sex did not have such an effect.

Conclusion: This study determined CID and PASS values for the KOOS, IKDC, and Lysholm scores among patients treated with knee cartilage restoration. Younger age was a positive prognostic variable, and higher baseline scores implied achieving PASS for the IKDC. The information in this study can be used in designing randomized controlled trials, counseling individual patients as to anticipated outcomes, and conducting responder analyses when evaluating new cartilage technology from a regulatory perspective.

Keywords: Patient Acceptable Symptomatic State; cartilage repair; cartilage restoration; clinically important difference; knee; patient-reported outcome measures.