Association between the Critical Shoulder Angle and Non-traumatic Rotator Cuff Tears

Abstract

Background: Moor et al. developed a critical shoulder angle (CSA) as a radiological parameter for the development of rotator cuff injury and degenerative changes of the glenohumeral joint. The objective of this study is to evaluate the association between CSA and the development of non-traumatic rotator cuff tears (RCTs) to further validate this study. Materials and Methods: The study was performed as an observational study dividing subjects into control and study groups, differing in the presence of non-traumatic RCT. The study group comprised 50 subjects with 40 subjects in the control group. All acceptable radiographs were evaluated, to measure the CSA in accordance with Moor et al. Results: The mean CSA of control subjects was 31.79° (± 1.89°), while that of study subjects were 37.85° (± 2.25°). The relative variability in the control group was about 6% and that in the study group was also 6%, indicating internal homogeneity of the study groups. Chi-square test applied to the distribution gave a P = 0.00001, representing an excellent association between the study groups and the CSA. Conclusion: There is a significant association between larger CSA and RCTs (P = 0.00001). Individual (quantitative) anatomical parameters may imply altered biomechanics, which are likely to induce RCTs, independent of trauma and degenerative glenohumeral joint disease.