Acromial Tilt, Lateral Acromial Angle, and Acromiohumeral Interval as Risk Factors for Full-Thickness Supraspinatus Tendon Ruptures.

Introduction The aim of this study was to investigate whether the morphology of the acromion and the inclination of the glenoid are associated with the risk of supraspinatus (SSP) tendon ruptures. Materials and methods A total of 106 patients were enrolled in this study between August 2012 and February 2014, including 55 symptomatic patients with an SSP tendon rupture (ruptured group) and 51 patients with an intact SSP (control group). MRI of the shoulder was performed for all patients in both groups. All MR images were analyzed by two blinded observers to measure the acromiohumeral interval (AHI), critical shoulder angle (CSA), acromial slope (AS), acromial tilt (AT), lateral acromial angle (LAA), acromion index (AI), and glenoid inclination (GI). Furthermore, both observers analyzed tendon integrity and quality on all MRIs in both groups. The results of the radiological examination concerning acromial and glenoidal morphology were compared between the control group with intact SSP tendons and the rupture group. Results Patients with an SSP tendon rupture had a narrower AHI (9.1 ± 1.4 mm vs. 7.8 ± 2.1 mm; p < 0.01), a greater AT (36.0 ± 5.4° vs. 39.7 ± 5.9°; p < 0.01), and a lower LAA (81.1 ± 7.2° vs. 76.2 ± 5.0°; p < 0.01). Patients with an AHI smaller than 8.2 mm (OR 1.88 [95% CI 1.2 to 2.7]; p < 0.01) or an AT greater than 36.5° (OR 3.56 [95% CI 1.57 to 8.01]; p = 0.03) or a LAA lower than 80.5° (OR 4.04 [95% CI 2.04 to 7.90]; p < 0.01) had higher risk for an SSP tendon rupture. No differences between either group were found in relation to the AS, CSA, AI, or glenoid inclination. Conclusions The results of this study showed that the AHI, LAA and AT correlated with SSP tendon rupture. It should be noted that the preoperative AHI less than 8.2 mm, AT greater than 36.5° or LAA less than 80.5° may be associated with SSP tendon ruptures.