Background: Outcomes assessment after the treatment of shoulder disorders has involved the use of various condition-specific outcome instruments. The purpose of this study was to determine the psychometric properties of the American Shoulder and Elbow Surgeons subjective shoulder scale in patients with shoulder instability, rotator cuff disease, and glenohumeral arthritis.
Methods: Test-retest reliability, internal consistency, content validity, criterion validity, construct validity, and responsiveness to change were determined for the American Shoulder and Elbow Surgeons shoulder scale within subsets of an overall study population of 455 patients with shoulder instability, 474 patients with rotator cuff disease, and 137 patients with glenohumeral arthritis.
Results: There was acceptable test-retest reliability for the overall American Shoulder and Elbow Surgeons shoulder scale (intraclass correlation coefficient = 0.94) and ten of eleven domains. There was acceptable internal consistency for patients with instability (Cronbach alpha = 0.61), rotator cuff disease (0.64), and arthritis (0.62). There were acceptable floor and ceiling effects for patients with instability (0% and 1.3%, respectively), rotator cuff disease (0% for both), and arthritis (0% for both). There was acceptable and appropriate criterion validity, with significant correlations (p < 0.05) between the overall American Shoulder and Elbow Surgeons scale and the physical functioning, role-physical, and bodily pain domains of the Short Form-12 scale, and nonsignificant correlations (p > 0.05) with the role-emotional, mental health, vitality, and social function domains. There was acceptable construct validity, with all twenty-three hypotheses demonstrating significance (p < 0.05), and acceptable responsiveness to change for patients with instability (standardized response mean, 0.93), rotator cuff disease (1.16), and arthritis (1.11).
Conclusions: The use of outcome instruments with psychometric properties that have been vigorously established is essential. The American Shoulder and Elbow Surgeons subjective shoulder scale demonstrated overall acceptable psychometric performance for outcomes assessment in patients with shoulder instability, rotator cuff disease, and glenohumeral arthritis.
1 Department of Orthopaedic Surgery, Children's Hospital Boston, 300 Longwood Avenue, Boston, MA 02115. E-mail address: firstname.lastname@example.org
2 Steadman Hawkins Research Foundation, 181 West Meadow Drive, Vail, CO 81657
3 Harvard Combined Orthopaedic Residency Program, Massachusetts General Hospital, 55 Fruit Street, Boston, MA 02114