Coracobrachialis muscle arises from the (deep surface of the) apex of the coracoid process of the scapula (a common origin with the short head of the biceps brachii[1][2]). It additionally also arises from the proximal portion of tendon of origin of the biceps brachii muscle.[1]
The coracobrachialis muscle has been classified into distinct superficial and deep layers.[4] In 16% of individuals the muscle is fully divided into these layers, in 8% of individuals there is incomplete separation, and in the 76% there is no discernible separation of the layers.[5]
The overuse of the coracobrachialis can lead to stiffening of the muscle. Common causes of injury include chest workouts or activities that require one to press the arm very tight towards the body, e.g. work on the rings in gymnastics.[7]
Symptoms of overuse or injury are pain in the arm and shoulder, radiating down to the back of the hand. In more severe cases, the musculocutaneous nerve can get trapped, causing disturbances in sensation to the skin on the radial part of the forearm and weakened flexion of the elbow, as the nerve also supplies the biceps brachii and brachialis muscles.[8]
Rupture of the coracobrachialis muscle is extremely rare. Very few case reports exist in the literature, and it is reported to be caused by direct trauma to the contracted muscle. Avulsion of the muscle's origin from the coracoid as a result of indirect forces is even more unusual.[9]
^ abcSinnatamby, Chummy S. (2011). Last's Anatomy (12th ed.). Elsevier Australia. p. 58. ISBN978-0-7295-3752-0.
^Spinner, Robert J. (2018-01-01), Morrey, Bernard F.; Sanchez-Sotelo, Joaquin; Morrey, Mark E. (eds.), "72 - Nerve Entrapment Syndromes", Morrey's the Elbow and its Disorders (Fifth Edition), Philadelphia: Elsevier, pp. 679–701, ISBN978-0-323-34169-1, retrieved 2021-01-08
^"Coracobrachialis Muscle." Anatomy, Function and Pathology. KenHub.
^Iannotti, Joseph P. and Gerald R. Williams. Disorders of the Shoulder: Diagnosis & Management, Volume 1 Philadelphia: Lippincott Williams and Wilkins, 2007. 271–73. Print.
This article incorporates text in the public domain from page 443 of the 20th edition of Gray's Anatomy (1918).
