Coracobrachialis Muscle Anatomy


The coracobrachialis muscle arises from the tip of the coracoid process. The coracobrachialis lies lateral to the pectoralis minor muscle. Close to the origin of the coracobrachialis is the origin of the coracoclavicular ligaments. The conoid ligament is medial and the trapezoid ligament is lateral. The coracobrachialis muscle inserts into the middle third of the medial border of the humeral shaft. The innervation of the coracobrachialis, biceps brachaii, and brachialis muscle comes from the musculocutaneous nerve. The brachialis has dual innervation. The medial part of the muscle innervation is from the musculocutaneous nerve and the lateral part of the muscle gets innervation from the radial nerve. The musculocutaneous nerve will also give the lateral antebrachial nerve with its anterior and posterior divisions. It is the primary nerve supply of the muscles of the anterior compartment of the upper arm, and it supplies sensation to the lateral half of the forearm. The coracobrachialis muscle flexes and adducts the arm at the shoulder joint. The coracobrachialis muscle originates from the coracoid, and the musculocutaneous nerve is close to the muscle. The musculocutaneous nerve pierces the coracobrachialis about 3-8 cm distal to the coracoid where it then gives a branch to the coracobrachialis muscle. Some studies show that the nerve may be 1-5 cm from the coracoid. The nerve runs between the biceps and the brachialis muscles on the anterior shoulder especially with retreaction of the conjoint tenson of the coracobrachialis and short head of the biceps. When the musculocutaneous nerve is injured, we may not be able to measure the deficit except for the decreased sensation on the area supplied by the lateral antebrachial cutaneous nerve, which is a terminal branch that will give sensation to the forearm. The lateral antebrachial cutaneous nerve could be injured during distal biceps repair. Be careful when retracting the conjoint tendon during  anterior shoulder sugery (avoid injury to the musculocutaneous nerve). Occasional, coracoid osteotomy is done to enhance exposure to the shoulder joint and the conjoint tendon will be easily retracted without compromising the musculocutaneous nerve

Nabil Ebraheim, MD

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