Background: The purpose of the present study was to validate the Functional Shoulder Score (FSS), a new patient-reported outcome score specifically designed to evaluate patients with rotator cuff disorders.
Methods: One hundred and nineteen patients were assessed using two shoulder scoring systems [the FSS and the Constant-Murley Score (CMS)] at 3 weeks pre- and 6 months post-arthroscopic rotator cuff surgery. The reliability, validity, responsiveness and interpretability of the FSS were evaluated.
Results: Reliability analysis (test-retest) showed an intraclass correlation coefficient value of 0.96 [95% confidence interval (CI) = 0.92 to 0.98]. Internal consistency analysis revealed a Cronbach's alpha coefficient of 0.93. The Pearson correlation coefficient FSS-CMS was 0.782 pre-operatively and 0.737 postoperatively (p < 0.0005). There was a statistically significant increase in FSS scores postoperatively, an effect size of 3.06 and standardized response mean of 2.80. The value for minimal detectable change was ±8.38 scale points (based on a 90% CI) and the minimal clinically important difference for improvement was 24.7 ± 5.4 points.
Conclusions: The FSS is a patient-reported outcome measure that can easily be incorporated into clinical practice, providing a quick, reliable, valid and practical measure for rotator cuff problems. The questionnaire is highly sensitive to clinical change.
Keywords: PROMs; reliability; rotator cuff disorders; shoulder questionnaires; validity.