Investigating minimal clinically important difference for Constant score in patients undergoing rotator cuff surgery

BACKGROUND: The minimal clinically important difference (MCID) is increasingly used to evaluate treatment effectiveness. The MCID for the Constant score has not been previously reported.

MATERIALS AND METHODS: A prospectively collected cohort of 802 consecutive shoulders with arthroscopically treated partial- or full-thickness rotator cuff tears was analyzed. The Constant score was measured preoperatively and at 3 months and 1 year postoperatively. At follow-up visits, the patients were asked a simple 2-stage question: Is the shoulder better or worse after the operation compared with the preoperative state? This single 2-level question was used as an indicator of patient satisfaction and as an anchor to calculate the MCID for the Constant score.

RESULTS: At 1 year, 781 (97.4%) patients (474 men, 307 women) were available for follow-up. The preoperative Constant score was 53.1 (SD 17.2) in all patients, 56.2 (SD 17.4) in male patients, and 48.2 (SD 15.6) in female patients. Postoperatively at 3 months, the scores were 61.7 (SD 16.4) in all patients, 65.1 (SD 16.1) in male patients, and 56.8 (SD 15.5) in female patients. At 1 year, the scores were 75.9 (SD 15.2) in all patients, 79.0 (SD 14.9) in male patients, and 71.0 (SD 14.3) in female patients. At 3 months postoperatively, 92.2% of male patients and 87.2% of female patients were satisfied with the outcome (P = .027); at 1 year, the satisfaction was 93.2% and 89.5%, respectively (P = .067). Five different statistical approaches yielded 5 different MCID estimates (range, 2-16). The 3-month mean change estimate of MCID was 10.4 points.

CONCLUSION: Our study demonstrates an MCID estimate of 10.4 points as the threshold for the Constant score in patients with rotator cuff tear.

LEVEL OF EVIDENCE: Basic science study, validation of outcomes instruments/classification systems.