AP: Upper Limb

• Framework: Overview and Surface Anatomy | The Shoulder Girdle and Joint | Rotator Cuff and Shoulder Movements | The Axilla and Breast Lymphatics | The Arm and Elbow | The Forearm | The Wrist and Hand
• Nerves and vessels: The Brachial Plexus | Median Nerve | Ulnar Nerve | Radial, Axillary and Musculocutaneous Nerves | Root Lesions — Myotomes and Dermatomes | Blood Supply and Venous Drainage | Clinically Important Injuries
• Revision: Upper Limb at a Glance | Spot the Diagnosis | Exam-style Scenarios | Key Points | Guidelines and Further Reading

💪 Upper limb anatomy — page 3 of the Anatomy and Physiology chapter. Upper limb anatomy is tested constantly — in nerve lesions (wrist drop, claw hand, carpal tunnel), fractures that damage nerves and vessels, the brachial plexus, and practical procedures (cannulation, blood gases, nerve blocks). Learn the nerves by what they supply and what happens when they are cut, and the anatomy becomes clinical medicine.
Your four questions for every upper limb problem: Is this a root, plexus, or peripheral nerve lesion? Which muscles are weak and which skin is numb? Which bone or joint injury puts which nerve or vessel at risk? What does the examination need to test to prove it?

Overview and Surface Anatomy

• Regions — shoulder (pectoral girdle), arm (brachium — shoulder to elbow), forearm (antebrachium), wrist (carpus), hand.
• Bones — clavicle, scapula, humerus, radius (lateral — thumb side), ulna (medial), 8 carpals, 5 metacarpals, 14 phalanges.
• Compartments:
  • Arm — anterior (flexors — musculocutaneous nerve) and posterior (extensors — radial nerve).
  • Forearm — anterior (flexors and pronators — mostly median, some ulnar) and posterior (extensors and supinator — radial / posterior interosseous).
• Surface landmarks:
  • Clavicle, acromion, coracoid process (below the lateral clavicle), spine of the scapula.
  • Medial and lateral epicondyles, olecranon — form a straight line in extension and a triangle in flexion (lost in elbow dislocation; preserved in supracondylar fracture).
  • Cubital fossa — from lateral to medial: biceps tendon, brachial artery, median nerve ("TAN") — antecubital veins overlie it (venepuncture).
  • Anatomical snuffbox — between extensor pollicis longus and the abductor/extensor brevis tendons — scaphoid lies in its floor; radial artery crosses it.
  • Radial pulse — lateral to flexor carpi radialis at the wrist (arterial blood gas sampling — check collateral flow with Allen's test).
• Anatomical position — palms facing forward; "lateral" is the thumb side.

The Shoulder Girdle and Joint

• Shoulder girdle — clavicle and scapula; the only bony attachment of the upper limb to the trunk is the sternoclavicular joint; the scapula moves on the chest wall (scapulothoracic "joint").
• Joints:
  • Sternoclavicular — posterior dislocation can compress the great vessels and trachea.
  • Acromioclavicular — injured by falls on the tip of the shoulder (AC joint separation — "step").
  • Glenohumeral — ball-and-socket synovial joint; very mobile but unstable (shallow glenoid, deepened by the labrum).
• Stabilisers of the glenohumeral joint — rotator cuff (dynamic), glenoid labrum, capsule and glenohumeral ligaments, long head of biceps.
• Dislocation — anterior (95% — abduction and external rotation) — risks axillary nerve injury; Bankart lesion (labral tear), Hill–Sachs lesion (humeral head impaction); posterior (seizures, electric shock).
• Clavicle fractures — commonest in the middle third; the lateral fragment is pulled down by the weight of the arm and the medial fragment up by sternocleidomastoid; subclavian vessels and brachial plexus lie below (rarely injured).
• Scapula — fractures imply high-energy trauma (check chest); winging — long thoracic nerve palsy (serratus anterior).
• Frozen shoulder (adhesive capsulitis) — loss of external rotation (active and passive); associated with diabetes.

Rotator Cuff and Shoulder Movements

• Rotator cuff — "SITS":

  Muscle	Action	Nerve	Test
  Supraspinatus	Initiates abduction (first 15°)	Suprascapular (C5–6)	Empty can (Jobe's) test
  Infraspinatus	External rotation	Suprascapular (C5–6)	Resisted external rotation
  Teres minor	External rotation	Axillary (C5–6)	Resisted external rotation (hornblower's)
  Subscapularis	Internal rotation	Upper and lower subscapular (C5–6)	Lift-off and belly-press tests

• Abduction — supraspinatus (0–15°), deltoid (15–90° — axillary nerve), then trapezius and serratus anterior rotate the scapula (above 90°).
• Other shoulder muscles — pectoralis major (adduction, internal rotation — medial and lateral pectoral nerves), latissimus dorsi (extension, adduction, internal rotation — thoracodorsal nerve), teres major, biceps and coracobrachialis (flexion).
• Subacromial impingement — supraspinatus tendon squeezed under the acromion — painful arc between about 60° and 120° of abduction.
• Rotator cuff tears — degenerative (over 40) or traumatic; weakness of abduction or rotation; ultrasound or MRI; massive tears in older people — "pseudoparalysis".
• Calcific tendinitis — acute severe pain, calcium deposit in supraspinatus on X-ray.
• Long head of biceps rupture — "Popeye" bulge in the arm; little functional loss.

The Axilla and Breast Lymphatics

• Axilla — a pyramid-shaped space between the arm and chest wall, transmitting vessels and nerves to the limb.
• Walls — anterior (pectoralis major and minor), posterior (subscapularis, teres major, latissimus dorsi), medial (serratus anterior and ribs), lateral (humerus — intertubercular groove); apex at the clavicle–first rib–scapula.
• Contents — axillary artery and vein, brachial plexus (cords and branches), axillary lymph nodes, fat; intercostobrachial nerve (numbness of the inner arm after axillary surgery).
• Axillary artery — first rib to the lower border of teres major; divided into 3 parts by pectoralis minor.
• Axillary lymph nodes — drain the upper limb, breast (about 75% of breast lymph) and chest wall above the umbilicus:
  • Groups — anterior (pectoral), posterior (subscapular), lateral (humeral), central, apical.
  • Surgical levels (relation to pectoralis minor) — level I (below/lateral), level II (behind), level III (above/medial — apical).
  • Sentinel lymph node biopsy — first node to drain the tumour (dye and radioisotope) — avoids full clearance if negative.
• Nerves at risk in axillary surgery:
  • Long thoracic nerve (C5–7 — serratus anterior) — winged scapula.
  • Thoracodorsal nerve (latissimus dorsi) — weak extension and adduction.
  • Intercostobrachial nerve — numb inner arm.
• Lymphoedema of the arm after axillary clearance or radiotherapy.
• Other breast drainage — internal mammary (parasternal) nodes (medial tumours), supraclavicular nodes.

The Arm and Elbow

• Humerus — nerves at risk:
  • Surgical neck — axillary nerve and posterior circumflex humeral artery.
  • Mid-shaft (spiral groove) — radial nerve → wrist drop.
  • Supracondylar — brachial artery and median nerve (anterior interosseous branch) — children.
  • Medial epicondyle — ulnar nerve.
• Muscles of the arm:
  • Anterior — biceps brachii (elbow flexion and supination — the main supinator when flexed), brachialis (main elbow flexor), coracobrachialis — all musculocutaneous nerve (C5–6).
  • Posterior — triceps (elbow extension) — radial nerve (C7).
• Elbow joint — hinge joint (humero-ulnar and humero-radial) plus the proximal radio-ulnar joint (pronation and supination — radial head turns in the annular ligament).
• Elbow problems:
  • Lateral epicondylitis ("tennis elbow") — common extensor origin — pain on resisted wrist extension.
  • Medial epicondylitis ("golfer's elbow") — common flexor origin.
  • Olecranon bursitis — gout, infection, trauma.
  • Pulled elbow — radial head subluxes through the annular ligament (children aged 1–4).
  • Radial head fracture — fall on outstretched hand — "fat pad sign" on X-ray.
  • Cubital tunnel syndrome — ulnar nerve compression at the elbow.
• Carrying angle — the forearm angles slightly outwards in extension (valgus — greater in women); altered after supracondylar malunion (cubitus varus — "gunstock" deformity).

The Forearm

• Anterior compartment — flexors of the wrist and fingers and pronators (in layers):
  • Superficial — pronator teres, flexor carpi radialis, palmaris longus (absent in about 15%), flexor carpi ulnaris (ulnar nerve) — from the medial epicondyle.
  • Intermediate — flexor digitorum superficialis (flexes PIP joints).
  • Deep — flexor digitorum profundus (flexes DIP joints — lateral half median/AIN, medial half ulnar), flexor pollicis longus (thumb IP — AIN), pronator quadratus (AIN).
• Nerve supply — all anterior forearm muscles by the median nerve except flexor carpi ulnaris and the medial half of FDP (ulnar).
• Posterior compartment — extensors of the wrist, fingers and thumb, supinator, brachioradialis — all radial nerve (or its deep branch, the posterior interosseous nerve).
• Testing flexor tendons — FDP (hold PIP straight, ask to bend the fingertip), FDS (hold other fingers straight, ask to bend the finger at the PIP) — after hand lacerations.
• Forearm fractures:
  • Monteggia — fracture of the proximal ulna with dislocation of the radial head.
  • Galeazzi — fracture of the distal radius with dislocation of the distal radio-ulnar joint ("MUGR" — Monteggia Ulna, Galeazzi Radius).
  • Both-bone fractures in adults usually need surgical fixation.
• Forearm compartment syndrome — after supracondylar fractures, crush injuries, tight casts — pain on passive finger extension — fasciotomy; untreated → Volkmann's ischaemic contracture (clawed, flexed fingers and wrist).

The Wrist and Hand

• Carpal bones (lateral to medial) — proximal row: scaphoid, lunate, triquetrum, pisiform; distal row: trapezium, trapezoid, capitate, hamate ("Some Lovers Try Positions That They Can't Handle").
• Scaphoid — commonest carpal fracture (fall on outstretched hand — young adults); snuffbox tenderness; blood supply enters distally → proximal pole at risk of avascular necrosis and non-union — immobilise and image (MRI) if suspected even with a normal X-ray.
• Lunate dislocation — can compress the median nerve; "spilled teacup" on lateral X-ray.
• Carpal tunnel — roof is the flexor retinaculum; contains the median nerve and 9 tendons (4 FDS, 4 FDP, FPL); flexor carpi radialis runs in its own compartment; ulnar nerve and artery pass outside (Guyon's canal).
• Intrinsic hand muscles:
  • Thenar (abductor pollicis brevis, flexor pollicis brevis, opponens pollicis) — median nerve (recurrent branch).
  • Hypothenar — ulnar nerve.
  • Lumbricals — flex the MCP and extend the IP joints — lateral two (index and middle) median, medial two ulnar.
  • Interossei — dorsal abduct (DAB), palmar adduct (PAD) the fingers — ulnar nerve.
  • Adductor pollicis — ulnar nerve (Froment's sign — thumb IP flexes to compensate when gripping paper).
• "LOAF" — the median nerve supplies the Lateral two lumbricals, Opponens pollicis, Abductor pollicis brevis and Flexor pollicis brevis; the ulnar nerve supplies all other intrinsic hand muscles.
• Hand conditions — Dupuytren's contracture (palmar fascia — ring and little fingers), trigger finger, de Quervain's tenosynovitis (APL and EPB — Finkelstein's test), ganglion, mallet finger (extensor tendon avulsion at the DIP), boutonnière and swan-neck deformities (rheumatoid arthritis), flexor sheath infection (Kanavel's signs).

The Brachial Plexus

• Formation — anterior rami of C5–T1; "Real Teachers Drink Cold Beer" — Roots (5) → Trunks (3 — upper C5–6, middle C7, lower C8–T1) → Divisions (6 — anterior and posterior) → Cords (3 — lateral, posterior, medial — named by relation to the axillary artery) → Branches.
• Course — between scalenus anterior and medius (with the subclavian artery), behind the clavicle, into the axilla.
• Terminal branches:

  Cord	Main branches	Roots
  Lateral	Musculocutaneous; lateral root of median	C5–7
  Medial	Ulnar; medial root of median; medial cutaneous nerves of arm and forearm	C8–T1
  Posterior	Axillary, radial; subscapular and thoracodorsal nerves	C5–T1

• Branches from roots — long thoracic nerve (C5–7 — serratus anterior; "C5, 6, 7 — raise your wings to heaven"), dorsal scapular (C5 — rhomboids), contribution to the phrenic nerve (C5).
• Branches from the upper trunk — suprascapular nerve (C5–6).
• Plexus lesions:
  • Erb's palsy (upper trunk — C5–6) — traction separating the head and shoulder (shoulder dystocia, motorbike falls) — "waiter's tip" — arm adducted and internally rotated, elbow extended, forearm pronated; loss of abduction, elbow flexion and supination; numb lateral arm.
  • Klumpke's palsy (lower trunk — C8–T1) — traction with the arm abducted above the head (grabbing a branch while falling, breech delivery) — claw hand (all intrinsics weak), numb medial forearm; may have Horner's syndrome (T1).
  • Pancoast tumour (lung apex) — invades the lower trunk and sympathetic chain — shoulder and arm pain, hand wasting, Horner's.
  • Cervical rib / thoracic outlet syndrome — compresses the lower trunk or subclavian vessels.
  • Neuralgic amyotrophy (Parsonage–Turner) — severe shoulder pain then patchy weakness and wasting.
• Regional anaesthesia — interscalene (shoulder — almost always blocks the phrenic nerve), supraclavicular, infraclavicular and axillary blocks.

Median Nerve

• Roots C5–T1 (mainly C6–8) — lateral and medial cords.
• Course — with the brachial artery in the arm (no branches in the arm) → cubital fossa (medial to the artery) → between the heads of pronator teres → deep to FDS → anterior interosseous nerve branch → carpal tunnel → recurrent motor branch (thenar) and digital nerves.
• Supplies — most forearm flexors and pronators; thenar muscles and lateral two lumbricals (LOAF); skin of the lateral palm and the palmar surface of the thumb, index, middle and lateral half of the ring finger (and their nail beds); palmar cutaneous branch arises before the carpal tunnel (palm sensation spared in carpal tunnel syndrome).
• Lesions by level:

  Level	Cause	Features
  Wrist (carpal tunnel)	Carpal tunnel syndrome, wrist lacerations, lunate dislocation	Thenar wasting, weak thumb abduction, numbness of the lateral 3½ fingers (palm spared); worse at night; Tinel's and Phalen's tests
  Anterior interosseous nerve	Supracondylar fracture, forearm trauma	Can't make an "OK" sign (weak FPL and index FDP — pinch with flat fingertips); no sensory loss
  Elbow and above	Supracondylar fracture, dislocation	All of the above plus weak forearm pronation and flexion — "hand of benediction" (index and middle fingers stay extended when trying to make a fist)

• Carpal tunnel syndrome — causes: idiopathic, pregnancy, hypothyroidism, diabetes, rheumatoid arthritis, acromegaly, obesity, amyloid (dialysis), wrist fractures — treatment: night splints, steroid injection, surgical decompression (division of the flexor retinaculum); nerve conduction studies confirm.

Ulnar Nerve

• Roots C8–T1 (medial cord).
• Course — medial arm → behind the medial epicondyle ("funny bone" — cubital tunnel) → between the heads of FCU → forearm (supplies FCU and medial half of FDP) → Guyon's canal (superficial to the flexor retinaculum, beside the pisiform) → deep motor branch and superficial sensory branch.
• Supplies — FCU, medial half of FDP, most intrinsic hand muscles (hypothenar, interossei, medial two lumbricals, adductor pollicis, deep head of FPB); skin of the medial 1½ fingers (front and back) and the medial hand.
• Ulnar claw hand — hyperextension of the MCP joints and flexion of the IP joints of the ring and little fingers (lumbricals lost; FDP unopposed).
• The ulnar paradox — the claw is worse with a distal (wrist) lesion than a proximal (elbow) lesion, because FDP to the ring and little fingers is still working and pulls the fingers into flexion.
• Signs — wasting of the first dorsal interosseous and hypothenar eminence, weak finger abduction and adduction (card test), Froment's sign, numb little finger; Wartenberg's sign (little finger abducted).
• Causes — compression at the elbow (cubital tunnel — leaning on the elbow, arthritis, valgus deformity — "tardy ulnar palsy"), medial epicondyle fractures, wrist lacerations, cyclists (Guyon's canal), leprosy.
• Ulnar vs C8–T1 root lesion — C8 root also weakens median-supplied thenar muscles and long finger flexors, and numbness extends up the medial forearm.

Radial, Axillary and Musculocutaneous Nerves

• Radial nerve (C5–T1, posterior cord):
  • Course — posterior arm in the spiral (radial) groove of the humerus → anterior to the lateral epicondyle → divides into the posterior interosseous nerve (motor — through supinator) and the superficial radial nerve (sensory).
  • Supplies — triceps, brachioradialis, all wrist, finger and thumb extensors, supinator; skin of the posterior arm and forearm and the dorsal web space between thumb and index finger.
  • Lesions:
    • Axilla (crutches) — triceps weak, wrist drop.
    • Spiral groove (mid-shaft humerus fracture, "Saturday night palsy") — wrist drop, triceps spared, numb dorsal web space.
    • Posterior interosseous nerve — finger drop (can't extend fingers at the MCP joints) but wrist extension largely preserved (ECRL spared) and no sensory loss.
    • Superficial radial nerve — tight watch straps or handcuffs (Wartenberg's syndrome) — numb dorsal thumb only.
  • Wrist drop makes grip appear weak (flexors can't work well with the wrist flexed) — test grip with the wrist supported.
• Axillary nerve (C5–6, posterior cord):
  • Winds around the surgical neck of the humerus (with the posterior circumflex humeral artery) through the quadrangular space.
  • Supplies deltoid and teres minor; skin over the lower deltoid ("regimental badge" area).
  • Injured in anterior shoulder dislocation and surgical neck fractures — weak abduction (15–90°), deltoid wasting — check sensation before and after reduction.
• Musculocutaneous nerve (C5–7, lateral cord) — pierces coracobrachialis; supplies biceps, brachialis and coracobrachialis; continues as the lateral cutaneous nerve of the forearm (skin of the lateral forearm) — rarely injured alone; weak elbow flexion and supination; absent biceps jerk.
• Long thoracic nerve — winging of the scapula (pushing against a wall) after axillary surgery, carrying heavy loads.

💡 Clinical Pearl: Three questions sort most hand nerve injuries: can the patient extend the wrist (radial), make an "OK" sign and abduct the thumb (median), and spread the fingers against resistance (ulnar)? Then map the numb skin.

Root Lesions — Myotomes and Dermatomes

• Cervical radiculopathy — root compression by a disc or osteophyte (spondylosis) — neck and arm pain in a dermatomal pattern, weakness, reduced reflex; C6 and C7 most common; Spurling's test (neck extension and rotation reproduces arm pain).
• Root vs nerve — C6 root vs median nerve (thumb numbness in both; C6 also weakens biceps and brachioradialis and reduces their reflexes); C8 root vs ulnar nerve (see above); C7 root vs radial nerve (C7 weakens triceps and wrist flexion too).
• Inverted supinator jerk — C5–6 cord compression — tapping brachioradialis causes finger flexion (brisk reflexes below the level) instead of elbow flexion.
• Cervical myelopathy — UMN signs in the legs, clumsy hands, Hoffmann's sign, Lhermitte's sign — urgent MRI.

Blood Supply and Venous Drainage

• Arteries — subclavian (left from the aortic arch; right from the brachiocephalic trunk) → axillary (outer border of the first rib) → brachial (lower border of teres major) → divides in the cubital fossa into radial and ulnar arteries → superficial (mainly ulnar) and deep (mainly radial) palmar arches.
• Pulses — brachial (medial to the biceps tendon — BP measurement), radial (wrist), ulnar (often hard to feel).
• Allen's test — occlude both radial and ulnar arteries, release the ulnar — colour should return within about 5–10 seconds — checks ulnar collateral supply before radial artery puncture or cannulation.
• Brachial artery injury — supracondylar fracture in children — pale, pulseless hand (or pink pulseless) — urgent reduction and vascular review.
• Subclavian steal syndrome — proximal subclavian stenosis → reversed flow in the vertebral artery when the arm is used → dizziness; BP difference between arms over 15–20 mmHg.
• Veins:
  • Superficial — cephalic (lateral — up the arm into the deltopectoral groove → axillary vein), basilic (medial — pierces deep fascia mid-arm → joins brachial veins → axillary vein), median cubital (links them in the cubital fossa — venepuncture).
  • Deep — venae comitantes alongside the arteries → axillary → subclavian vein.
  • PICC lines — usually the basilic vein; AV fistulas for dialysis (radiocephalic, brachiocephalic) — protect the non-dominant arm in CKD.
  • Upper limb DVT — lines, pacing wires, thoracic outlet (Paget–Schroetter — effort thrombosis).
• Lymphatics — superficial vessels follow the veins → epitrochlear nodes (medial elbow) and axillary nodes.

Clinically Important Injuries

• Colles' fracture — distal radius, dorsal displacement ("dinner fork" deformity) — fall on outstretched hand in older women (osteoporosis); Smith's fracture — volar displacement (fall on a flexed wrist); Barton's — intra-articular with carpal subluxation.
• Fragility fractures (distal radius, proximal humerus) — assess for osteoporosis (FRAX, DEXA) and falls.

Upper Limb at a Glance