Coracoid Process

By September 22, 2015Upper Extremity

Introduction

The coracoid process is a finger like projection from the scapula. It projects anteriorly and laterally. The coracoid process serves as an attachment point for muscles and helps to stabilize the clavicle and shoulder joint via ligaments. It runs in close proximity to the glenohumeral joint. Because of this, it can be confused for the head of the humerus. The coracoid process is an interesting structure because it is a connection between the arm, shoulder, and anterior chest wall.

Muscles

The coracoid process has three muscle attachments. Pectoralis minor attaches ribs 3-5 to the coracoid process. Coracobrachialis attaches from the upper 1/3 of the body of the humerus to the coracoid process. Finally, the short head of the biceps brachii attaches to the coracoid process while the long head attaches to the superior aspect of the glenoid. At its other end, the biceps brachii attaches to the radial tubercle and bicipital aponeurosis into deep fascia on the medial part of the forearm. The pectoralis minor is innervated and pierced by the medial pectoral nerve (C6-T1). Extramural fibers from the nerves innervating the intercostal muscles communicate with the medial pectoral nerve. The biceps brachii and coracobrachialis are innervated by the musculocutaneous nerve.

Ligaments

There are 5 ligaments from the coracoid process involved with limiting the motion of the clavicle and acromion. The coracoclavicular ligament (formed by the conoid and trapezoid ligament) limits the movement of the clavicle. Conoid and trapezoid are attached to each other. The trapezoid is the anterior portion and conoid is posterior. Both attach to undersurface of the clavicle. Considered part of AC joint even though it is not actually part of the joint because of its importance in maintaining the relationship of the joint.

The coracoacromial ligament forms a vault protecting the head of the humerus. It is located deep to the deltoid and has the supraspinatus tendon deep to it. The coracohumeral ligament attaches from the base of the coracoid process to the lesser and greater tubercle of the humerus blending with the tendon of supraspinatus. It is also a part of the shoulder joint capsule.

Posteriorly, there is the superior transverse scapular ligament, which has the suprascapular nerve (innervate supraspinatus and infraspinatus)  that runs between it and the suprascapular notch. The position of the scapula on the rib cage may have an effect on the suprascapular nerve passing under the ligament. The costocoracoid ligament is  the thick lateral border of the coracoclavicular fascia extending from the coracoid process to the cartilage of the first rib.

Fascia

Fascially, the clavicopectoral fascia is deep to the deep layer of the pectoral fascia. There is loose connective tissue between them to allow the fascias to glide independently of each other. The clavicopectoral fascia arises from the clavicle and envelops the pectoralis minor and subclavian muscles. There is a triangular shaped layer of the clavicopectoral fascia from the upper border of pectoralis minor to the clavicle named the coracoclavicular fascia. The coracoclavicular fascia is pierced by the thoracoacromial artery, the lateral pectoral nerve, and the cephalic vein. The clavicopectoral fascia continues laterally to help form the axillary fascia and the fascia of the coracobrachialis muscle. Superiorly, deep layer covering the subclavius muscle blends with the deep cervical fascia. Medially the coracoclavicular fascia extends from the coracoid process to the cartilage of the first rib with its thick lateral border named the costocoracoid ligament.

Nerves

The cords of the brachial plexus run medial to the body of the coracoid process and run deep to the pectoralis minor muscle and between the rib cage. The musculocutaneous nerve runs medially to the coracoid process and pierces the coracobrachialis muscle. It often has motor branches that pierce the coracobrachialis muscle prior to the main nerve.

Lymphatics

The axillary lymphatic plexus runs in close proximity to the coracoid process. They collect lymph from the arm, deltopectoral, and lateral thoracic regions on their way to left and right thoracic ducts.

Osteopathic Considerations

As with any structure, it is always important to understand normal versus abnormal anatomy. As a rule of thumb, always palpate and compare both sides to feel how they compare in motion, sensitivity, asymmetry, and anything else that stands out. Always recheck after treatment to evaluate what, if any, effect the treatment has had.

With the patient supine, find the coracoid process just inferior to the lateral clavicle and medial to the head of the humerus. Spring on the coracoid process to assess what motion the coracoid process has. Usually a more restricted coracoid process will feel denser and be more sensitive than a properly working coracoid process. The clavicle will often feel less mobile when the coracoid process feels restricted. This has to do with the coracoclavicular and coracoacromial ligaments being taut likely from the dysfunctions.

The coracoid process is part of the scapula and with any structure of the shoulder, an important place to consider first is the rib cage and thoracic spine. The rib cage is the base upon which the shoulder sits. If the shoulders are pulled forward, it may be due to one side or both sides of the rib cage being stuck in extension or a rotational curve in the spine and ribs, or exaggerated kyphosis of the thoracic spine.

Pectoralis Minor

The purpose for treating the pectoralis minor is to improve rib cage mechanics and help get the scapula more appropriately situated on the rib cage. Having the scapula appropriately positioned on the rib cage can help release any tension on the suprascapular nerve going through the suprascapular notch under the transverse scapular ligament. Releasing the pectoralis minor can also help release intercostal muscles deep to them or vice versa. The purpose is not just because its ability to influence the rib cage and pull the coracoid anteroinferomedially, but also to help release the clavicopectoral fascia.

Releasing the clavicopectoral fascia can help release the subclavius muscle which may then help improve rib 1 motion. This can help if there is a compression of the neurovascular bundle between the pectoralis minor and rib 1. In addition the coracoclavicular fascia has the thoracoacromial artery, cephalic vein, and lateral pectoral nerve piercing them. In addition this can help improve lymphatic drainage in the region. Normalizing function of the ribs can down regulate any facilitation of the medial pectoral nerve piercing the pectoralis minor and have an effect on the sympathetic chain ganglia sitting on the posterior rib heads as rib function is improved. A release of these structures associated with the coracoid process can can help improve shoulder, arm, and rib cage mechanics.

Costocoracoid ligament

The purpose for treating the costocoracoid ligament is to further help improve rib cage mechanics. Furthermore, this is meant to help release the coracoclavicular fascia which forms this ligament. Releasing this can also help release the subclavius muscles and pectoralis minor through the fascia.

Lateral Release of Shoulder

The purpose of this is to reposition the shoulder complex more appropriately on the rib cage. This can help get pressure off of the rib cage, allow the fascia to unwind, and let the muscles involved to relax. This will allow better expansion of the upper rib cage during inhalation. Releasing a medial shoulder often allows the trapezius to relax as it attaches to the clavicle and scapula. The abnormal medial position of the scapula may cause it to form knots. This release can help improve lymphatic drainage by creating more space and less tension in the region.

Elbow Joint

The purpose of releasing the elbow joint is to improve the function of the elbow and as a result, get the biceps brachii to relax. A dysfunctional elbow will affect the muscles associated with the joint, including the biceps. Besides treating the ulna’s motion on the trochlea of the humerus, it is important to treat the head of the radius as the biceps directly attaches to the radial tubercle. The biceps attaches to the medial forearm via the bicipital aponeurosis and into the deep fascia of the forearm. Releasing the biceps can help get pressure off of the coracoid process and overall shoulder.

Normalizing function at the elbow can help downregulate any facilitation of the musculocutaneous nerve arising from C5-7 and help normalize the sympathetic innervation in the upper extremities from T2-8. At times, releasing the elbow will improve motion of the rib cage.

Coracoclavicular Ligament

The clavicle is important not just as an often overlooked component of the shoulder, but also as an attachment point for muscles and the clavicopectoral fascia. As a result the position of the clavicles can produce tensions through the fascia that result in bad posture. In this case, we are trying to free restricted movement of the clavicle on the coracoid process. This can help free fascial planes and improve shoulder motion by helping the clavicle move better through its normal motions.

Glenohumeral Joint

The glenohumeral joint often feels compressed where the head of the humerus is internally rotated and may be pulled superiorly and compressed under the acromion in the vault formed by the coracoacromial ligament. This will have an effect on the shoulder muscles and fascia associated with it. This can cause the biceps brachii and coracobrachialis among other muscles to be hypertonic by facilitating the musculocutaneous nerve. Releasing the axillary fascia can help release the clavicopectoral fascia and the fascia enveloping coracobrachialis.

Furthermore, an abnormal relationship here can make the coracohumeral ligament to be taut and put tension on the shoulder joint capsule. The shoulder can be influenced by the axillary fascia. Releasing the axillary fascia can also improve axillary lymphatic drainage. The purpose of releasing the glenohumeral joint is to release and normalize these structures when dysfunctional.

Coracoacromial Ligament

A strain pattern in the coracoacromial ligament can be indicative of an intraosseous strain of the scapula. This can change the amount of space the head of the humerus has in the vault that is created by the ligament. This can be affected by the head of the humerus being anterior. After relocating the head of the humerus on the glenoid, then we can work to normalize the coracoacromial ligament and by releasing an intraosseous strain, a more correct shape to the vault can be achieved. This can help to help maintain the optimal position of the glenohumeral joint.

References

Flatow EL1, Bigliani LU, April EW. An anatomic study of the musculocutaneous nerve and its relationship to the coracoid process. Clin Orthop Relat Res. 1989 Jul;(244):166-71. http://www.ncbi.nlm.nih.gov/pubmed/2743658

Koizumi M1, Horiguchi M. [A study on the communication between the pectoral nerve and the extramural nerve branches of the intercostal nerves]. Kaibogaku Zasshi. 1992 Oct;67(5):606-15. [Article in Japanese] http://www.ncbi.nlm.nih.gov/pubmed/1462753

Rios CG, Arciero RA, Mazzocca AD. Anatomy of the Clavicle and Coracoid Process for Reconstruction of the Coracoclavicular Ligaments Am J Sports Med May 2007 35 811817.  http://www.ncbi.nlm.nih.gov/pubmed/17293463

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