A Morphological and Morphometric Analysis of a Acromion Process on Dry Human Scapulae.

Abstract

INTRODUCTION

The acromion is one of the most variable portions of the scapula. It is associated with a variety of shoulder disorders. The morphology, morphometric and angular parameters of the acromion process can be beneficial in the surgical resection of the acromion process. Medical professionals and researchers need to have a thorough understanding of the morphometry and morphology of the acromion process.

AIMS AND OBJECTIVES

The present study aimed to measure the morphometric and morphological characteristics of the acromion process in dried human scapulae.

MATERIALS AND METHODS

A cross-sectional study was conducted on 77 undamaged adult dry scapulae with complete acromion processes from the Department of Anatomy, National Institute of Medical Science and Research (India), after ethical approval (Letter No. IEC/P-842/2024). Morphological measurements were visually analyzed. Linear measurements were taken using a digital vernier caliper (0.01 mm accuracy) and averaged; angular measurements were obtained using Digimizer 6.4.7software.

     RESULT

We have observed that in the morphological characteristics, the quadrangular shape of the acromion was more common (53.2%). Examination of the inferior surface revealed that the majority of acromion had a rough surface (88.3%). Osteophytes were present in 85.7% on the acromion. In subacromial shape, rhomboid configuration was predominant (81.8%), followed by triangular (13.0%) and trapezoid (5.2%) shapes. In acromion angle, the L-shaped acromion was the most common (67.5%), followed by the C-shaped (29.9%) and double-C type (2.6%). The mean length of the acromion process was 33.03 ± 9.91 mm, with a median value of 35.20 mm and an average range of 4.48–51.10 mm. The mean width of the was 22.26 ± 3.93 mm. The mean thickness of the acromion process measured at three different points (T1, T2, and T3) was 5.15 ± 1.52 mm, 5.34 ± 1.82 mm, and 5.35 ± 1.86 mm, respectively. The mean acromion-coracoid distance (LAC) was 37.64 ± 7.15 mm, while the mean acromion-glenoid distance (LAG) was 28.76 ± 4.77 mm. The mean height of the coracoacromial arch was 16.92 ± 6.61 mm. The mean distance of the Spino glenoid notch (XY) was 17.36 ± 3.31 mm. The mean distance from the acromion tip to point X (LAX) was 34.73 ± 5.78 mm, and the mean distance from the coracoid to point Y (LCY) was 43.86 ± 4.91 mm. With respect to angular parameters, the mean lateral acromial angle (LAA) was 68.77 ± 14.03°, and the mean critical shoulder angle (CSA) was 30.30 ± 11.05°. The mean acromial slope (AS) and acromion tilt (AT) were 33.87 ± 9.43° and 37.01 ± 7.75°, respectively.

CONCLUSION

The remarkably low prevalence of Type III hooked acromion (2.6%) distinguishes this cohort from populations exhibiting higher rates of this pathological variant. Morphometric measurements revealed that mean values generally fall below established clinical risk thresholds. Lateral acromial angle of 68.77° approached but remained above the 70° risk threshold, suggesting intermediate biomechanical characteristics. Multiple linear regression identified lateral acromial angle as the strongest independent predictor of critical shoulder angle (β = 0.451, p < 0.001), validating this parameter's central role in determining shoulder joint biomechanics and rotator cuff loading characteristics. Significant side-wise variations in measurements suggest functional adaptation to dominant limb usage patterns and underscore the importance of bilateral shoulder assessment in clinical evaluation.