Chapter 48: Pectoral Girdle & Upper Limb

Pectoral Girdle & Upper Limb provides a comprehensive overview of the pectoral girdle and upper limb, detailing its role as a series of powered, articulated segments engineered to accurately position the hand for sensing and manipulation, with movement capacity enhanced by the unique capability of approximately 180 degrees of pronation and supination inherent to the primate limb. The skeletal structure includes the scapula, clavicle, humerus, radius, ulna (interconnected by the interosseous membrane), the carpus, metacarpals, and phalanges, all articulating through joints such as the single direct bony attachment at the sternoclavicular joint and the highly mobile, shallow glenohumeral joint, stabilized by powerful musculature. Organization within the soft tissues relies on the deep fascia and intermuscular septa, which partition the limb into discrete compartments, a system crucial for isolating structures and relevant clinically for understanding the spread of infection and the potentially devastating pathology of compartment syndrome. The primary arterial supply traces from the subclavian artery, becoming the axillary artery at the first rib, then the brachial artery, before dividing into the radial and ulnar arteries, which rely on extensive anastomotic collateral circulation, particularly around the joints. Venous drainage is achieved through superficial veins, like the cephalic and basilic veins, linked by the median cubital vein, and deep venae comitantes. The rich and complex innervation is derived from the brachial plexus (C5 through T1 spinal ventral rami), which forms the major terminal nerves—Axillary, Radial, Median, Ulnar, and Musculocutaneous—all of which follow predictable myotomal and dermatomal territories critical for neurological diagnosis. Clinical evaluations rely on palpating skeletal landmarks and pulses, interpreting specific signs like Horner’s syndrome or intense radiating pain indicative of preganglionic injury, and utilizing diagnostic tools like Tinel’s sign to locate postganglionic ruptures. Furthermore, the chapter explores pathological conditions associated with restricted spaces, such as the acute compartment syndromes in the forearm or axilla, and the diverse manifestations of thoracic outlet syndromes, which often involve vascular or neural compression related to anomalies like a seventh cervical rib.