--- module: 076-02 language: en chapter: 76 title: "Back, Spinal Column, Upper Limb, and Lower Limb Anatomy" module_title: "Upper-limb osteology, joints, muscles, vessels, and nerves" source_sha256: 47855b928705ec8465ff8c9269fa45ea1e1c0ae07ce925d8a54cd49af4abcc28 --- # Upper limb anatomy ## Mobility over bony stability ### Reach, orientation, manipulation ### Mobile scapula and shallow shoulder socket ### Learn by compartments, actions, routes, injury sites ## Shoulder girdle and axial connection ### Clavicle: only bony link to trunk #### Curves hold shoulder away from thorax #### Fracture threatens vessels, plexus, lung ### Glenoid shallow, deepened by labrum ### Scapulothoracic motion made by muscles ### Coracoclavicular ligaments suspend the limb #### Disruption causes separation, altered mechanics ### Elevation combines glenohumeral and scapular motion #### Scapulohumeral rhythm is not a fixed ratio #### Weak serratus or trapezius disrupts upward rotation ## Dynamic shoulder stability ### Large humeral head on small glenoid ### Static: labrum, capsule, ligaments, negative pressure ### Dynamic: rotator-cuff compression, scapular muscles #### Supraspinatus initiates and supports abduction #### Infraspinatus, teres minor externally rotate #### Subscapularis internally rotates ### Anterior-inferior dislocation in abduction, external rotation #### Axillary nerve at risk near surgical neck #### Recurrence: labral detachment, head impaction ### Subacromial pain has several sources #### Acromial shape alone does not prove cause ## Arm and cubital fossa ### Septa divide flexor and extensor compartments ### Musculocutaneous nerve supplies anterior arm ### Radial nerve in radial groove with profunda brachii #### Vulnerable in humeral-shaft injury ### Brachial artery divides into radial and ulnar ### Cubital fossa contents lateral to medial #### Biceps tendon, brachial artery, median nerve #### Bicipital aponeurosis protects during venepuncture ### Elbow collateral ligaments resist valgus and varus #### Annular ligament holds the radial head ## Forearm rotation and compartments ### Radius crosses ulna in pronation ### Interosseous membrane transmits load, separates compartments ### Anterior flexors mostly median nerve #### Flexor carpi ulnaris, medial profundus ulnar #### Anterior interosseous: pollicis longus, pronator quadratus ### Posterior extensors and supinator by radial nerve #### Deep branch through supinator as posterior interosseous #### Compression: extension weakness, little sensory loss ### Palmar arches vary, assess collateral circulation ## Wrist and carpal tunnel ### Scaphoid bridges carpal rows #### Fall on extended hand #### Retrograde supply risks proximal-pole necrosis ### Carpal tunnel: median nerve and nine flexor tendons ### Ulnar nerve and artery in Guyon canal ### Median compression: lateral three and a half digits #### Thenar and lateral lumbrical weakness #### Palmar branch superficial, palm may be spared ## Hand mechanics and innervation ### Metacarpophalangeal collaterals tighten in flexion ### Lumbricals flex MCP, extend IP via expansions ### Dorsal interossei abduct, palmar adduct ### Median nerve provides precision ### Ulnar nerve supplies most intrinsics for power grip ### Radial nerve supplies no intrinsic hand muscles ### Superficialis to middle, profundus to distal phalanx #### Mallet, boutonniere, jersey at specific levels ## Brachial plexus ### C5 to T1 ventral rami #### Trunks between anterior and middle scalenes #### Divisions behind clavicle, cords around axillary artery ### Root lesion affects parts of several nerves ### Upper trunk: abduction, external rotation, elbow flexion ### Lower trunk: intrinsic hand, possible Horner syndrome ### Long thoracic: serratus weakness, medial winging ## Trauma and compression ### Surgical neck threatens axillary nerve ### Humeral shaft threatens radial nerve ### Medial epicondyle threatens ulnar nerve ### Supracondylar threatens brachial artery, median fibres ### Forearm compartment pressure threatens perfusion #### Repeat neurovascular examination ### Thoracic outlet: scalene, costoclavicular, pectoralis minor #### Provocative tests are nonspecific