Minimal clinically important difference in the Japanese Orthopedic Association Score and shoulder 36 after arthroscopic rotator cuff repair in a Japanese population: A retrospective cohort study.

Background: In Japan, the Japanese Orthopedic Association (JOA) score is widely used as a clinician-reported outcome after shoulder surgery. However, Shoulder36 is positioned as a general patient-reported outcome measure. This study aimed to determine the correlations between the JOA score and scores in the domains of the Shoulder36 and their minimal clinically important differences (MCIDs) and cutoff values for the patient-acceptable symptom state (PASS) after unilateral arthroscopic rotator cuff repair (ARCR).

Methods: We evaluated 145 patients using the JOA score and Shoulder36 before and 1 year after surgery. The MCID and PASS cutoff values were determined by patients' responses to the following anchor item: A, none ("no good at all"); B, poor ("some effect but unsatisfactory"); C, good ("satisfactory effect with occasional episodes of pain or stiffness"); D, excellent ("ideal response, virtually pain-free"). The correlations between the JOA score and the domains of the Shoulder36 were statistically calculated. The border between B and C was defined as the threshold for PASS.

Results: There were significant correlations between the JOA score and the Shoulder36 domains. The responses to the anchor item were as follows: A (n = 0), B (n = 21), C (n = 76), and D (n = 48). The MCID for the JOA score was 19.5 points and the MCIDs for Shoulder36 were 0.5 points for pain, 0.667 for range of motion, 0.67 for muscle strength, 0.3 for general health, 0.571 for activities of daily living, and 1.0 for sports ability. The PASS cutoff value was 89.0 points for the JOA score and 3.8 points for pain, 3.667 for range of motion, 3.0 for muscle strength, 3.7 for general health, 3.7 for activities of daily living, and 3.0 for sports ability in the Shoulder36.

Conclusions: The MCID and cutoff PASS values for the JOA score and Shoulder36 identified in this study will help to determine the effectiveness of multidisciplinary management after ARCR.