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The acromion forms the summit of the shoulder and is a large, somewhat triangular or oblong process, flattened from behind forward. It projects laterally at first, then curves forward and upward to overhang the glenoid fossa. [2] It starts from the base of acromion which marks its projecting point emerging from the spine of scapula. [3]
The two muscles most commonly inhibited during this first part of an overhead motion are the serratus anterior and the lower trapezius. [10] These two muscles act as a force couple within the glenohumeral joint to properly elevate the acromion process, and if a muscle imbalance exists, shoulder impingement may develop.
It gives attachment to the capsular ligament of the shoulder joint except at the upper inferior-medial aspects. It is best marked in the lower half of its circumference; in the upper half it is represented by a narrow groove separating the head of the humerus from the two tubercles, the greater tubercle and the lesser tubercle .
The SSB bursa is located deep to the deltoid muscle and the coracoacromial arch and extends laterally beyond the humeral attachment of the rotator cuff, anteriorly to overlie the intertubercular groove, medially to the acromioclavicular joint, and posteriorly over the rotator cuff.
The acromion is a bony process at the end of the scapula. The shoulder is a complex mechanism involving bones, ligaments, joints, muscles, and tendons. The two main causes are acute injury or chronic and cumulative degeneration of the shoulder joint. Mechanisms can be extrinsic, intrinsic or a combination of both. [27]
The acromioclavicular joint, or AC joint, is a joint at the top of the shoulder. It is the junction between the acromion (part of the scapula that forms the highest point of the shoulder) and the clavicle . [ 1 ]
The coracoacromial ligament is a strong triangular ligament between the coracoid process and the acromion. It protects the head of the humerus. Its acromial attachment may be repositioned to the clavicle during reconstructive surgery of the acromioclavicular joint (shoulder joint).
They are inserted into the medial margin of the acromion, and into the superior lip of the posterior border of the spine of the scapula. The inferior or lower (or ascending) fibers of the trapezius arise from the spinous processes of the remaining thoracic vertebrae (T4–T12).