It is divided into three segments in relation to the insertion of the scalenus anterior muscle. The vertebral artery branches out in the first segment, and the costocervical trunk and thyrocervical trunk branch out in the second segment. No branches are found in the third segment. The thyrocervical trunk gives rise to the transverse scapular artery and the suprascapular artery, which are mostly found in dissections involving the shoulder girdle Fig. The subclavian artery continues as the axillary artery distally to supply the entire upper extremity.
Borrowed from Netter FH. Atlas of Human Anatomy, page , 6th edition. Saunders, Philadelphia, PA. It forms from C5 through T1 cervical roots and exits the neck through the interval between the anterior and middle scalene. The five cervical roots form three trunks that separate into the anterior and posterior divisions. As the brachial plexus crosses beneath the clavicle it gives rise to three cords.
The medial cord derives from the eighth cervical and first thoracic roots and forms a branch of the median nerve, the medial pectoral nerve, the entire ulnar nerve, and the medial cutaneous nerve. A lateral cord deriving from the fifth, sixth, and seventh cervical roots forms the lateral pectoral nerve, musculocutaneous nerve, and another branch of the median nerve. Both the medial and lateral cords are anterior whereas the posterior cord of the plexus forms the upper and lower subscapular, thoracodorsal, axillary, and radial nerves.
The medial cord passes between the first rib and medial third of the clavicle. It is vulnerable to compression in this location so much so that severe trauma can lead to proximal ulnar neuropraxia [ 12 ].
The clavicle serves as a solid barrier protecting the plexus from traumatic injury. Lippincott, Williams and Wilkins.
Havet et al. The intermediate ramus courses below platysma and divides into two or three terminal branches. The lateral ramus courses in a frontal plane toward the acromion process crossing the anterior belly of the trapezius. This ramus is probably the nerve that supplies the acromioclavicular joint as reported by Ebraheim et al. Information regarding the anatomy of the supraclavicular nerves may help in preventing potential injury to these branches during surgery about the clavicle, especially during open reduction and internal fixation of midshaft clavicle fractures.
The supraclavicular nerves are pure sensory nerves that supply sensation over the clavicle, the anteromedial shoulder, and the proximal chest. Although the precise locations of the principal rami and terminal branches are variable, there are safe zones extending 2. Nevertheless, preserving branches of the supraclavicular nerve remains a major challenge during the surgical approach to the clavicle because these lie in close proximity to its anterior surface. Even when the branches are identified they are often injured from repetitive stretch due to retraction or manipulation.
Blood Supply to the Clavicle The main blood supply of the clavicle is periosteal involving mainly the anterior and superior surfaces [ 13 ]. A secondary blood supply is intramedullary and canalicular, but this is of secondary importance. The prominent periosteal perfusion underscores the importance of minimizing dissection and avoiding periosteal stripping during the treatment of clavicle fractures, whether by intra-medullary or plate fixation.
Clavicle Biomechanics The clavicle serves as a point of insertion for two muscles: the trapezius and subclavius and the point of origin for four muscles: the deltoid, pectoralis, sternocleidomastoid, and sternohyoid. However, the biomechanical role of the clavicle, in terms of overall shoulder motion and strength is not entirely understood. Proponents of total clavicular resection during tumor surgery or after multiple failed fracture surgeries point to the absence of substantial functional deficits postoperatively, if claviculectomy is performed with careful muscle repair.
However, the clavicle functions as a strut that allows shoulder motions such as cross body adduction and internal rotation, and also serves as a bony arch that protects major neurovascular structures. By assuming the role of a strut, the clavicle permits the scapulohumeral and the scapulothoracic muscles to work at their optimal lever arms, thereby improving muscle efficiency and minimizing energy expenditure and muscle fatigue.
In addition, the clavicle serves a suspensory role that prevents the shoulder from drooping down due to the weight of the arm and avoids the recruitment of stabilizing muscles such as the trapezius from overcompensating to level both shoulder girdles. Thus, it largely contributes to the superior shoulder suspensory complex from which the upper extremity is suspended [ 18 ].
Key Takeaways Key Points The clavicle is a long, doubly curved bone that connects the arm to the body, located directly above the first rib. It acts as a strut to keep the scapula in place so the arm can hang freely.
The clavicle is an attachment point for several muscles. Structurally, the clavicle can be divided into three parts: medial end, lateral end, and shaft. There are sex differences in clavicle shape—female clavicles are shorter and thinner than male clavicles. Key Terms acromion : The outermost point of the shoulder blade.
Scapula The scapula, or shoulder bone, is a flat, triangular bone that connects to the humerus and the clavicle. Learning Objectives Describe the shape and function of the scapula in humans. Key Takeaways Key Points The scapula articulates with the humerus and the clavicle. The scapula is flat and triangular. The scapula articulates with the humerus at the glenoid fossa and the clavicle at the acromion process. The scapula provides attachment sites for many muscles including the pectoralis minor, coracobrachialis, serratus anterior, triceps brachii, biceps brachii, and the subscapularis.
The scapula has two main surfaces: the costal front facing surface and the dorsal rear facing surface. Dorsal surface : Dorsal surface of the left scapula. Licenses and Attributions. CC licensed content, Shared previously. The clavicle or collar bone is a long, curved bone on the upper portion of the shoulder that connects with the scapula and the sternum.
The clavicle, or collarbone, is a slender s-shaped bone that extends between the sternum and the scapula and is located directly above the first rib. It functions to attach the upper arm to the trunk and provides support to allow free movement around the shoulder.
Left Clavicle : The left clavicle, viewed from above. Muscle attachment sites pectoralis major, subclavius muscle, deltoid, and sterno-hyoid are highlighted. Medially the clavicle is quadrangular in shape and articulates with the manubrium of the sternum forming the sternoclavicular joint.
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