Investigating the multifactorial etiology of supraspinatus tendon tears.

The purpose of this study was to develop a multivariable model to determine the extent to which a combination of etiological factors is associated with supraspinatus tendon tears. Fifty-four asymptomatic individuals (55 ± 4 years) underwent testing of their dominant shoulder. Diagnostic ultrasound was used to assess for a supraspinatus tendon tear. The etiological factors investigated included demographics (age and sex), tendon impingement during shoulder motion (via biplane videoradiography), glenohumeral morphology (via computed tomography imaging), family history of a tear (via self-report), occupational shoulder exposure (via shoulder job exposure matrix), and athletic exposure (via self-report). Univariate relationships between etiological predictors and supraspinatus tears were assessed using logistic regression and odds ratios (ORs), while multivariable relationships were assessed using classification and regression tree analysis. Thirteen participants (24.1%) had evidence of a supraspinatus tear. Individuals with a tear had a higher critical shoulder angle (OR 1.2, p = 0.028) and acromial index (OR 1.2, p = 0.016) than individuals without a tear. The multivariable model suggested that a tear in this cohort can be explained with acceptable accuracy (AUROC = 0.731) by the interaction between acromial index and shoulder occupational exposure: a tear is more likely in individuals with a high acromial index (p < 0.001), and in individuals with a low acromial index and high occupational exposure (p < 0.001). The combination of an individual's glenohumeral morphology (acromial index) and occupational shoulder exposure may be important in the development of supraspinatus tears.