Acromion

The acromion is a bony process on the scapula (shoulder blade). Together with the coracoid process, it forms the acromioclavicular joint, articulating with the clavicle (collarbone). This joint is a key component of the shoulder girdle, connecting the upper limb to the trunk.

The acromion projects laterally, overhanging the glenohumeral joint (shoulder joint). It provides attachment points for several muscles, including the deltoid and trapezius. Its superior surface is subcutaneous, meaning it lies just beneath the skin and can be easily palpated.

The shape of the acromion can vary significantly between individuals. Common morphological variations include flat, curved, and hooked shapes. These variations have been implicated in shoulder impingement syndrome, a condition where the rotator cuff tendons are compressed against the acromion during arm elevation. A more hooked acromion is associated with a higher risk of impingement.

The acromion is a common site for osteoarthritis and other degenerative changes, particularly in older adults. Fractures of the acromion can occur due to direct trauma, such as a fall onto the shoulder. Treatment for acromion fractures typically involves immobilization and pain management, but surgery may be required in cases of significant displacement or instability.