Posterior Cervical Triangle

The posterior cervical triangle (posterior triangle of the neck) ( Fig. 5-1 ) is included because it houses the major neurovascular structures that supply the upper extremity and is the site of various clinical problems that can affect these structures and, potentially, the entire limb. The boundaries of this triangle are easily palpated and in most people can be identified visually. The base of the triangle is bony and formed by the middle third of the clavicle; the two sides are muscular and formed by the posterior border of the sternocleidomastoid and the superior border of the trapezius. The borders of these muscles converge as they are followed superiorly toward the mastoid process. These boundaries can be accentuated by hunching the shoulder anteriorly and superiorly (trapezius) and rotating the head to the opposite side (sternocleidomastoid).

Anterolateral view of the left posterior cervical triangle. To accentuate the sternocleidomastoid muscle, the head is rotated to the opposite side.

The floor of the triangle is muscular and palpable deep in the triangle. The subclavian artery and proximal part of the brachial plexus (roots or trunks) pass through this floor and are palpable in the anteromedial corner of the triangle (i.e., where the sternocleidomastoid muscle attaches to the clavicle). In the triangle, the subclavian artery is positioned medially and inferiorly; its pulse can be felt in the angle formed by the clavicle and sternocleidomastoid, just posterior to the clavicle where the artery passes superior to the first rib. The superior trunk of the brachial plexus is located approximately 2 to 3 cm superior to the clavicle at the posterior border of the sternocleidomastoid muscle. This structure feels like a strong cord or rope. Even though the accessory nerve is not palpable, its superficial course across the posterior triangle can be approximated because its course parallels a line between the earlobe and the acromion process.

Shoulder

The term shoulder ( Figs. 5-2 through 5-5 ) is nonspecific because the areas and structures that can be included vary considerably. In this discussion, the “shoulder” includes the clavicle, the scapula, the proximal portion of the humerus, and all related articulations and soft tissues.

Anterior view of the left shoulder, pectoral region, and proximal aspect of the arm.

Posterior view of the cervical and upper thoracic portions of the back and the scapular regions. Horizontal abduction of the abducted upper limbs is resisted to reveal certain of the intrinsic and extrinsic muscles of the shoulder. Because the upper limbs are moderately abducted, the scapulae are rotated somewhat superiorly.

Anterior and slightly inferior view of the left shoulder and axillary region. The arm is moderately abducted to reveal both the anterior and posterior axillary folds and the medial neurovascular bundle.

Superolateral view of the right shoulder.

The clavicle is palpable throughout its length. In the midline, the suprasternal (jugular) notch is easily felt just superior to the manubrium of the sternum and between the medial ends of the clavicles. The sternoclavicular joint is located just lateral to the notch; its location can be verified by circumducting the arm and thereby moving the clavicle at the joint. From the joint, the shaft of the clavicle can be followed laterally; medially, it is anteriorly convex, and laterally, it is anteriorly concave. The clavicle ends laterally at the acromioclavicular joint, which is marked by either an elevation or a “step-off.” The infraclavicular fossa is the depression inferior to the concavity of the clavicle; the coracoid process is palpable in the depths of that fossa.

The acromion process is the bony shelf just lateral to the acromioclavicular joint. The lateral border of this process ends abruptly and marks the most superior and lateral aspects of the scapula. The posterior aspect of the acromion continues medially and somewhat inferiorly as the spine of the scapula. The spine then ends medially, at its blunted base, at the medial (vertebral) border of the scapula. The base of the spine of the scapula typically is at the level of the spinous process of the third thoracic vertebra. From the base of the spine, the medial border of the scapula can be followed superiorly to the superior angle and inferiorly to the inferior angle. Most of the medial border is palpated through the trapezius muscle. From the inferior angle, the lateral (axillary) border can be followed superiorly to the glenoid fossa, which cannot be palpated.

Those aspects of the proximal humerus that can be palpated must be felt through the deltoid muscle around the edge of the acromion process. Because the head of the humerus articulates with the glenoid fossa of the scapula, it is positioned inferior to the acromion and therefore cannot be palpated. Even though the head of the humerus is not palpable, the tubercles surrounding it are. These are the greater tubercle laterally and posteriorly and the lesser tubercle anteriorly. These structures are separated by the intertubercular groove, which is positioned anterolaterally. The position of this groove can be verified by rotation of the humerus. The deltoid tuberosity is easily located on the lateral aspect of the shaft of the humerus, at about the midshaft level.

The muscles of the shoulder region can be classified as extrinsic and intrinsic. The extrinsic muscles interconnect the scapula, clavicle, or humerus with the axial skeleton and function to stabilize and move the shoulder girdle. Those that are palpable are the trapezius, pectoralis major, serratus anterior, and latissimus dorsi. The trapezius can be both visualized and palpated. The curvature of the neck between the head and the shoulder is formed by its superior part, and the middle and inferior parts extend laterally from the vertebral column and are superficial to most of the scapula. This muscle is prominent and easily palpable when the scapula is adducted. The pectoralis major forms the entire pectoral region, can be felt inferior to most of the clavicle, and forms the anterior axillary fold. It is active with horizontal adduction of the arm. The latissimus dorsi forms the most inferior part of the posterior axillary fold and can be palpated just lateral to the axillary border of the scapula, particularly when the arm is extended. The serratus anterior arises from the anterolateral aspects of most ribs and extends posteriorly and superiorly toward the vertebral border of the scapula. Because the muscle is largely deep to the scapula, only its anterior and inferior aspects can be felt. Forced scapular protraction (as during a push-up) makes these points of attachment easily identified. The rhomboid major and minor are located deep to the trapezius between the scapula and the vertebral column. Contraction of these muscles can be felt only when they are active and the trapezius is not, as when the scapula rotates inferiorly (i.e., during resisted extension of the arm). The levator scapulae also is deep to the trapezius, specifically its superior part, as it extends from the superior angle of the scapula to the upper cervical vertebrae. Even though this muscle is ropelike in shape, as opposed to the broader trapezius, it can be difficult to distinguish from the trapezius because both muscles elevate the scapula.

The intrinsic muscles of the shoulder extend from the scapula or clavicle to the humerus and function to stabilize the glenohumeral joint and move the humerus. The largest of these is the deltoid, which forms the entire contour of the shoulder. Its three parts are easily palpable: the middle part with abduction of the arm, the anterior part with flexion, and the posterior part with extension. The teres major extends from the inferior aspect of the axillary border of the scapula to the anterior aspect of the proximal humerus; posteriorly, it is superior to the latissimus dorsi and forms part of the posterior axillary fold. Resisted medial rotation or extension of the humerus makes this stout muscle easily visible and palpable. Palpation of the rotator cuff muscles is difficult because they are covered (at least partially) by larger muscles, specifically the deltoid and trapezius. The tendons of all four muscles can be located through the deltoid, where they insert on the tubercles of the humerus. The subscapularis inserts anteriorly on the lesser tubercle, the supraspinatus superiorly on the greater tubercle, and both the infraspinatus and teres minor posteriorly on the greater tubercle. When external rotation of the humerus is resisted, portions of the muscle bellies of both the infraspinatus and the teres minor can be felt on the posterior aspect of the scapula in the interval between the deltoid and the teres major.

The interval between the lateral aspect of the acromion process and the humerus, the suprahumeral (or subacromial ) space, is important clinically because it is most often the site of pain associated with an impingement syndrome. The soft tissue structures in this interval and deep to the deltoid muscle are the subacromial (subdeltoid) bursa, the tendon of the supraspinous muscle, and the superior aspect of the glenohumeral joint capsule. Even though each of these structures is palpable, each is palpated simultaneously with the others. As a result, distinguishing them is difficult. The tendon of the long head of the biceps brachii muscle also passes through this space. It is positioned somewhat anteriorly and is largely under the acromion, so it is palpable only in the intertubercular groove of the humerus.

Most neurovascular structures in the shoulder region are difficult to palpate because they are separated from the surface by a variety of other structures. However, the main neurovascular bundle that supplies the upper limb passes through the axilla, where it can be palpated with the arm moderately elevated. This bundle consists of the axillary artery and the median, ulnar, and radial nerves.