Patient Acceptable Symptom State, Treatment Failure, and associated KOOS thresholds at 3 months after arthroscopic meniscal surgery

Introduction
Thresholds indicating treatment success or treatment failure for relevant Patient Reported Outcomes Measures following arthroscopic meniscal surgery remain scarce. We investigated the proportion of patients perceiving their 3-months postoperative symptoms to be acceptable (PASS) or reflect a treatment failure (TF), and determined Knee Injury and Osteoarthritis Outcome Score (KOOS) subscale scores corresponding to achieving PASS and TF.

Materials and Methods
614 patients undergoing arthroscopic meniscal surgery from The Knee Arthroscopy Cohort Southern Denmark were included. PASS and TF cut-offs were calculated for the KOOS subscales and KOOS₄ (the mean of KOOS Pain, Symptoms, Sport/Recreation, and Quality of life subscale scores) using an anchor-based methodology and receiver operating characteristics statistics with the Youden Index to identify the optimal thresholds. Sensitivity analyses were performed stratifying by age (≤40/>40) and by surgery type.
Results277 patients (45%) achieved Patient Acceptable Symptom State, and 116 patients (19%) perceived the treatment had failed. 221 patients (36%) reported an undecided intermediate state. Established PASS/TF values for the KOOS subscales were 76/71 for Pain, 70/55 for Symptoms, 80/71 for ADL, 48/33 for Sport/Recreation, 53/47 for QOL, and 63/52 for KOOS₄, respectively. Sensitivity analysis revealed altered KOOS PASS and TF subscale thresholds depending on age group.
ConclusionThree months post surgery , 45% achieved Patient Acceptable Symptom State, while 19% perceived the treatment had failed. The presented KOOS thresholds can be used to evaluate the short-term success rates after meniscal surgery in group-based data. Application of additional methodological approaches is needed to confirm the results.