Morphometry and Morphology of the Acromion Process and Its Implications in Subacromial Impingement Syndrome.

Introduction Subacromial impingement syndrome (SIS) is a common shoulder disorder characterized by pain and limited range of motion in the shoulder joint. It is frequently attributed to the compression or impingement of the rotator cuff tendons and bursa between the humeral head and the acromion process of the scapula during arm elevation. Subacromial impingement syndrome may arise as a result of the morphology of the acromion process, a bony protrusion at the top of the scapula that is important in the biomechanics of the shoulder joint. In order to detect potential anatomical differences that can predispose people to subacromial impingement syndrome, medical professionals and researchers need to have a thorough understanding of the morphometry and morphology of the acromion process. Aims and objectives The aim of the present study was to measure the morphometric and morphological characteristics of the acromion process in dried human scapulae that belonged to the North Indian population. Materials and methods This was a cross-sectional study that was carried out on 120 undamaged adult human scapula, of which 52 belonged to the right side and 68 belonged to the left side. Our study focused on analyzing the morphology of the acromion process as well as determining its maximum length, maximum breadth, acromio-coracoid distance, acromio-glenoid distance, and thickness. A statistical analysis of the observed parameters was carried out using the chi-square test and independent t-test with the help of Statistical Package for the Social Sciences (SPSS, IBM Corp., Armonk, NY) 24.0. Statistical significance was set at 0.05 (if the P-value ≤ 0.05, it is significant). Results We observed that the quadrangular shape (51.67%) of the acromion process was most commonly reported in our study, while the tubular (9.99%) shape was the least common. The difference in the incidences of various shapes of the acromion process on the right and left sides of the scapula was found to be statistically significant (p-value ≤ 0.05). In this study, the curved or type II acromion process was the most common type (53.34%) observed, while the least common shape reported was the hooked type (18.33%). The average length of the right acromion process was 44.52±6.61 mm, and the left acromion process was 45.13±6.35 mm. For the breadth, the right acromion had an average value of 28.31±4.67 mm, while the left had an average of 28.34±4.92 mm. The thickness of the right acromion measured 7.10±1.73 mm, and the left acromion was 7.53±1.44 mm. The acromio-coracoid distance on the right side was 34.59 ± 6.47 mm, and the left side was 37.46±6.22 mm. The acromio-glenoid distance was measured to be 32.31±5.87 mm on the right side and 33.18±5.39 mm on the left side. Conclusions Planning and carrying out an acromioplasty require an understanding of the morphometric parameters of the acromion process. Although there is a paucity of research on its morphometric evaluation in the North Indian population, the surgeons would be able to use these data as a reference.