Abstract
The coracoacromial ligament (CAL), which restrains superior displacement of humeral head, connects the acromion and coracoid process. Due to the ligament's variations and its role in shoulder pain, CAL was investigated in this study. Sixty shoulders of 34 cadavers, from persons aged 61-98 (80.95 ± 8.81) years at death time, were dissected. The lengths of lateral (LBL) and medial borders (MBL), widths of acromial (AIW) and coracoid insertions (CIW), and thicknesses of lateral (LSTAI) and medial (MSTAI) sides of acromial insertions were measured by digital caliper. The data were subjected to statistical analysis. 24 (40%) V-shaped, 12 (20%) broad-banded, 9 (15%) quadrangular, 9 (15%) Y-shaped, and 6 (10%) multiple-banded types were identified. The mean total LBL, MBL, AIW, CIW, LSTAI, and MSTAI were 34.94 ± 4.59 mm, 33.58 ± 5.31 mm, 29.82 ± 9.48 mm, 12.62 ± 3.95 mm, 1.29 ± 0.17 mm, and 0.90 ± 0.22 mm, respectively. The mean LBL (39.12 ± 4.29 mm), MBL (36.48 ± 3.9 mm), and CIW (37.01 ± 3.39 mm) were significantly greatest in quadrangular type (p<0.001). The mean AIW was slightly greatest in quadrangular type (p=0.069). The mean LSTAI was significantly greatest in multiple-banded type (1.45 ± 0.10 mm, p<0.001) whereas the mean MSTAI was significantly greatest in quadrangular type (1.23 ± 0.23 mm, p<0.001). CAL is quite variable regarding morphology, dimensions, and insertion features. Despite common knowledge, MSTAI and MBL of CAL can be greater than lateral counterparts in some types. To obtain complete release of CAL at acromion, the clearance of ligament fibers in an area with the dimensions of around 16 mm in mediolateral and 15 mm in anteroposterior direction, beginning from the lateral edge of acromial insertion, is recommended.
Highlights
The shoulder joint is a highly mobile and complicated joint connecting upper extremity and thorax [1]
All types of coracoacromial ligament (CAL) variations were observed in this study: Yshaped type in 9 shoulders (15%; 3 from male, 6 from female cadavers) (Figure 1(a)), broad-banded type in 12 shoulders (20%; 3 from male, 9 from female cadavers) (Figure 1(b)), quadrangular type in 9 shoulders (15%; 6 from male, 3 from female cadavers) (Figure 1(c)), V-shaped type in 24 shoulders (40%; 12 from male, 12 from female cadavers) (Figure 1(d)), and multiple-banded type in 6 shoulders (10%; all from female cadavers) (Figure 1(e))
The mean lateral border length (LBL), medial border length (MBL), and coracoid insertion width (CIW) measurements were significantly greatest in quadrangular type
Summary
The shoulder joint is a highly mobile and complicated joint connecting upper extremity and thorax [1]. Shoulder pain occurs in up to 67% of the population at least once in lifetime [2]. Its accurate diagnosis is difficult due to unique anatomy of the shoulder joint [1]. During regular glenohumeral joint motion, all rotator cuff muscles operate harmoniously and stabilize the humeral head to the center of glenoid fossa [3]. Rotator cuff dysfunction (i.e., weak dynamic stabilization of humeral head) and elevation of humeral head by deltoid muscle activity are suggested to cause subacromial impingement (SAI) which is a common musculoskeletal system problem and one of the most frequent causes of shoulder pain, significantly reducing the life quality and work capacity of individuals [4, 5]. Narrowing of the subacromial space due to various external causes (such as hooked acromion, os acromiale, osteophytes of acromioclavicular joint) leads to SAI, which can result in rotator cuff tendinitis and consequent cuff tear as well [3, 6]
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