Acromion morphology affects lateral extension of acromion: A three-dimensional computed tomographic study

Objective: Morphological variation of the acromion and the lateral extension of the acromion (LEA) may contribute to the development of Rotator cuff tears. The aim of this study was to evaluate the effect of acromion morphology on the LEA by three-dimensional computed tomography (3D-CT) reconstruction. Methods: A total of 120 patients with a bilateral shoulder in the radiology department of our affiliated hospital from January 2021 to May 2021 were collected. Mimics 21.0 software was used to construct the 3D model of the scapula. The morphological parameters of the LEA were measured. The correlation between LEA and acromial morphology was analyzed. Results: There were two different types of LEA in the population, large acromial lateralization (31.43 +/- 0.18 mm) and short acromial lateralization (27.48 +/- 0.24 mm). There were no statistically significant differences in LEA among different ages and genders (P > 0.05). The average LEA measured on the right side (30.46 +/- 0.25 mm) was significantly higher than that on the left side (28.81 +/- 0.21 mm) (P < 0.05). It was a significant positive correlation between the left and the right side of the LEA in different acromial morphology (R = 0.904, P < 0.001). The LEA of the hooked acromion (32.81 +/- 0.22 mm) was significantly higher than that of the flat acromion (26.38 +/- 0.28 mm) and the curved acromion (29.74 +/- 0.15 mm) (P < 0.05). Conclusion: There were two types of LEA, large acromial lateralization and short acromial lateralization. The parameters of the large LEA are significantly related to the hooked acromion.