Radiographic Assessment of the Critical Shoulder Angle, the Lateral Acromion Angle and the Acromial Index in a Sample of Normal Adult Individuals: A Cross-Sectional Analytical Study

Background: Several radiological parameters used to assess the shoulder joint; among these, the critical shoulder angle (CSA), acromion index (AI), and lateral acromion angle (LAA) are widely used. Objectives: the primary objective of our study was to establish a reference value for these parameters among healthy Iraqi adults, and secondly to explore the influence of some anthropometric parameters on these shoulder parameters. Materials and Methods: the CSA, AI, and LAA were measured for all participants using AP radiographs of the shoulder joints on both sides, the anthropometric parameters were also recorded. The data were tabulated and statistically analyzed. Results: the study shows no statistically significant differences in the measurements of CSA, AI, or LAA between males and females and also no differences between right and left sides. There was a weak correlation between the CSA measures and all anthropometric parameters, while there was a strong positive correlation between AI measures both age and body weight. Conversely, the LAA showed significant negative correlations with age and BMI. Interestingly we found that age was a major predictor of both AI and LAA, while weight and BMI were predictors CSA. Conclusion: The findings of our study suggest that critical shoulder angle is relatively constant shoulder parameters among individuals, however acromial index and the lateral acromial angle vary with age and BMI, and this may affect the biomechanics of the shoulder.