The link of acromion morphology, and other potential factors, to rotator cuff tear in Addis Ababa, Ethiopia: a matched case-control study

Abstract Objective. To investigate the association between rotator cuff tears (RCT) and acromion morphology, utilizing magnetic resonance imaging (MRI). Subjects and methods. This was a matched case-control study, conducted in St. Paul’s Hospital Millenium Medical College in Addis Ababa, Ethiopia. The study recruited a total sample of 80 patients, comprising 40 cases diagnosed with RCT and 40 matched controls without RCT, over a two-year period (2018–2020). The relationship between acromion morphology and other predictor variables with RCT was examined using McNemar’s test and conditional logistic regression. Variables which demonstrated P-values ≤ 0.25 in the bivariable analyses were included in the final multivariable analysis. Statistical significance of variables in the final model were determined at P-value < 0.05. Adjusted odds ratios (AORs), with 95% confidence interval (CI), were reported on the link of the predictor variables to RCT. Results. Among cases, type I, type II, type III, & type IV acromion accounted for 32.5%, 55%, 15%, and 2.5%, respectively. Supraspinatus tear was the most common type of tear, accounting for 85% of RCT. McNemar’s test revealed a statistically significant difference in the proportions of acromion spurs, Os acromiale, and acromio-humeral distance (AHD) ≤ 7 mm between cases and controls (P-value < 0.001). After controlling covariate factors, AHD ≤ 7 mm further demonstrated a statistically significant association with RCT (AOR = 2.36; 95% CI = 1.13, 4.92; P-value = 0.02). Conclusion. AHD, adjusted for side of the shoulder, type of acromion, acromial spur, and Os acromiale, showed statistically significant association with rotator cuff tear.