The facts about the acromion process are dealt in this article. The acromion is a small, yet important part/extension of the scapula. Information about this scapular extension is presented in the following paragraphs.
The acromion process is one of the bones in the human body, present on the scapula. It is found together with the coracoid process. The acromion extends over the shoulder joint. An extension of the scapular spine, the acromion, together with the clavicle forms the acriomioclavicular joint.
The superior surface of this bone is convex in shape. It is directed backwards, lateral, and also upwards. The surface is rough and provides space for the attachment of the Deltoideus fibers. The superior surface is convex in shape, the inferior one is concave and smooth. The structure of the acromion process can also be described with the help of information about medial and lateral borders. The lateral border is irregular and thick. This border is generally lined by 3-4 tubercles. These tubercles are the points from which the Deltoideus originate. The shape of the medial border is concave; it is shorter in length if compared to the lateral one. A portion of the trapezius is attached to the medial border. The acromial end of the clavicle articulates with the medial border at an oval surface.
Functions of the Acromion Process
The formation of the acriomioclavicular joint is the main function of the acromion. A joint known as the gliding joint (one of the types of synovial joints) is formed at the point where the inside or medial border meets the lateral (flattened) end of the clavicle. The Sliding movement of the acromion against the clavicle results into the action of arm movement (raising above the head). This shoulder part also functions as a site of muscle attachment. From the lateral border of acromion, originate the fibers of middle deltoid. These fibers help in laterally lifting the arm.
Acromion Process Fracture
Fractures are classified as Type 1, Type 2, Type 3, and Stress fractures. The fractures under Type 1 are sub-divided into Type 1A and Type 2B. Type 1 category fractures require less time for healing. These are also known as avulsion fractures. It means that tearing or pulling action is the cause behind these bone fractures. Minimal displacement can be observed in fractures of Type 1B. These fractures are caused by trauma. Different forms of displacement result into the Type 2 acromion fractures. The displacement can be lateral as well as superior/anterior. Reduction in the subacromial doesn’t take place due to the Type 2 fractures. One can move the joint fully within 6 weeks of the nonoperative treatment. Reduction in the subacromial space is the main characteristic of Type 3 fractures. An acromial fracture that results into inferior displacement is the cause of Type 3. Shoulder pain caused by this kind of a fracture is greater than that of other fractures. Even after carrying out the treatment, one experiences significant amount of pain. Stress fractures are observed only rarely.
This is the most common type of injury to the shoulder area. This syndrome results from compression of soft tissues present between the acromion/coracoid process and the humerus head. When the arm is raised above the shoulder, the space between the acromion process and the tendons reduces, causing an impingement (rub against each other) leading to pain and irritation. Complications which result from shoulder impingement include rotator cuff tears, endinosis, bone spurs, caclific tendinitis or subacromial bursitis. Tissues that are subject to compression include the following: coracohumeral ligament, glenohumeral joint capsule (upper margin), biceps brachii tendon, supraspinatus muscle-tendon unit, and subacromial bursa.
This joint structure is an important part of the shoulder, which lies at a location that influences its movements. Fractures and wear & tear of this part causes pain as a result of compression of underlying tissues.
Treatment and Rehabilitation
The treatment for injuries related to this part vary according to the severity of the injury. The first line of treatment is rest, where the action using this part of the body is limited. As stated earlier, the most common injury to this is caused when there is strain on the shoulder when the arm is repeatedly raised above it. The doctor may advise the patient to restrict arm movements above the shoulder.
Non-steroidal anti-inflammatory medication can be given to ease the pain and the swelling of the local bone and soft tissue. Physical therapy is also useful. Stretching exercises are practiced to improve the range of motion, as this helps in increasing the gap between the process and the soft tissue around, hence relieving the pain. However, if these don’t work, steroids can be injected to the surrounding soft tissue to relieve the pain.
Surgery is the last line of treatment when the non-surgical treatments fail to give relief from the pain. Here, a part of the inflamed soft tissue, and sometimes a part of the bone itself, can be removed. Recovery can take 2-4 months, and in some cases, a whole year for complete relief from pain. The shoulder will be put in a sling to restrict movement, and this aids in faster healing, post-surgery. Rehabilitation exercises will be given to increase the strength and range of motion slowly.
*Process: It is an outgrowth of tissue from a larger bone/tissue.
Lateral: To the left or the right side away from the body (sideways).