Nazım KARAHAN, Barış YILMAZ, Ahmet ÖZTERMELİ, Murat KAYA, Serda DUMAN, Esin Derin ÇİÇEK

Evaluation of critical shoulder angle and acromion index in patients with anterior shoulder instability and rotator cuff tear

Objective: The aim of this study was to evaluate glenohumeral morphologic differences and their correlation betweenglenohumeral instability and rotator cuff pathology.Methods: Two-hundred radiographs and 100 MRI scans of 100 patients in whom the diagnosis of Anterior Shoulder Instability(Anl) or Rotator Cuff Tear (RCT) was arthroscopically verified were retrospectively identified and included in the study. All thepatients were categorized into two groups: 50 patients with Anl (23 female, 28 male; mean age = 29 ± 7.4) and 50 patients withRCT (28 female, 22 male). Two separate control groups were then formed, one of which included contralateral shoulders ofpatients in the AnI group, and the other consisted of contralateral shoulders of patients in the RCT group. The x-ray and MRIscans were examined by an orthopedic surgeon and a radiologist. The Acromial Index (AI) and the Critical Shoulder Angle (CSA)were measured on true anteroposterior shoulder radiographs; Glenoid Inclination (GI), Glenoid Version (GV), and AcromionAngulation (AA) were measured on MRI.Results: In the AnI group, the measurements were as followed: AI, 0.66 ± 0.03; CSA, 33 ° ± 2.85; GI, 3.4° ± 6.2; GV, 4.1 ± 4.3; andAA, 12.9 ± 8.3. In the RCT group, AI 0.71 ± 0.04; CSA, 36° ± 2.69; GI, 9.1 ± 5; GV, 6.7 ° ± 5.7; and AA, 14.3° ± 8.7. A moderatecorrelation was found between CSA and GI (r = 0.41, P = 0.001) and between AI and GI (r = 0.42, P = 0.014). A weak correlationwas found between AI and GI in the AnI group (r = 0.22, P = 0.001). The inter- and intra-observer intraclass correlationcoefficients were respectively 0.81 and 0.84 for AI, 0.88 and 0.92 for CSA, 0.72 and 0.76 for GI, 0.69 and 0.73 for GV, and 0.72and 0.77 for AA.Conclusion: The results of this study have shown that lower AI, GI, and antevert GV may be associated with AnI. InvestigatingCSA, AI, and GV could be useful for diagnostic evaluation of patients with AnI.Level of Evidence: Level III, Diagnostic Study

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