Definition

By: Gregory R. Waryasz, MD

The coracobrachialis muscle of the musculoskeletal system is characterized by being an important landmark in the shoulder because of how the musculocutaneous nerve pierces it.

It is part of the arm.  It consists of skeletal muscle fibers.

Its unique structural features include its elongated shape and location in the superomedial arm.  The musculocutaneous nerve pierces it.  The distal part of the coracobrachialis muscle is near the nutrient foramen of the humerus.

The origin is the tip of the coracoids process of the scapula.

The insertion is the middle third of the medial humerus.

The blood supply is from the brachial artery and venous drainage is from the accompanying veins.

The innervation is from the musculocutaneous nerve.

The coracobrachialis muscle as well as all other bones, muscles, and ligaments of the body are derived of mesodermal origin in the embryo.

The function of the coracobrachialis is to help to flex and adduct the arm.  It plays a role in resisting dislocation of the shoulder specifically in the downward direction.  The synergists include the pectoralis major, biceps brachii, and the anterior portion of the deltoid.

Diseases  are not commonly described, but there can be compression of the median nerve or brachial artery by the muscle.  There are case reports of an accessory coracobrachialis muscle that can lead to injury to other structures during regional anesthesia nerve blocks or surgery because the anatomical landmarks are different and changed.

Commonly used diagnostic procedures include clinical history, physical exam, and MRI.

References

Lieberman J (ed), AAOS Comprehensive Orthopaedic Review, American Academy of Orthopaedic Surgeons, 2008.

Moore K, Dalley A (eds), Clinically Oriented Anatomy (5th edition), Lippincott Williams & Wilkins, Philadelphia, PA, 2006.

Wheeless’ Textbook of Orthopaedics: Coracobrachialis (http://www.wheelessonline.com/ortho/coracobrachialis)