Glenoid Bone Stock and Rotator Cuff Pathology: Correlation and Inter-rater Analysis

BACKGROUND: Glenoid bone stock and morphology and rotator cuff muscle quality and tendon integrity are all important factors affecting the outcome of total shoulder arthroplasty. We hypothesize that the severity of glenoid bone loss correlates with rotator cuff tendon pathologies and severity of fatty infiltration of the rotator cuff musculature. METHODS: We retrospectively reviewed 45 CT scans of 44 patients (mean age 62 years; range 22 to 77 years) who underwent shoulder CT for primary shoulder pain. Measurements of glenoid bone loss, bone stock, version and joint line medialization were assessed on a 2-dimensional CT image in the axial plane after correction in the scapular plane. Measurements were defined by use of the Friedman line to approximate the surface of the paleoglenoid. Glenoid version was measured by Friedman technique. Glenoid morphology was assigned by modified Walch classification. Rotator cuff muscle fatty infiltration was assessed by MRI and each muscle assigned a Goutallier score. MRI was used to assess rotator cuff tendon tears. RESULTS: There was a statistical difference in the Goutallier score for the supraspinatus and infraspinatus muscle fatty infiltration between Walch subtypes (p < 0.05). There was statistical difference in the severity of subscapularis tendon tear between different Walch subtypes (p < 0.05). Degree of anteversion, anterior glenoid and medial glenoid bone loss correlate to subscapularis tendon tear severity (p<0.05). Anterior bone loss and joint-line medialization correlate to increased fatty infiltration of the subscapularis muscle (p<0.05). Degree of retroversion correlates to glenoid bone loss at all points and glenohumeral joint-line medialization (p<0.05). B2, B3 glenoids have significantly greater bone loss at all points (anterior, middle and posterior), whereas D type glenoids exhibited greater anterior and middle bone loss compared to other Walch classes. CONCLUSIONS: B2, B3 and D type glenoids are correlated with greater bone loss compared to other Walch sub-types. High-grade tears of the subscapularis tendon correlated to greater pathologic anteversion, and anterior and posterior glenoid bone loss. Anterior bone loss and joint-line medialization was correlated to increased fatty infiltration of the subscapularis muscle. Pathologic retroversion correlates to global increase in bone loss and humeral head medialization. Further studies are required to determine the casual relationships between glenoid bone loss and subscapularis tendon tears.