Applied Anatomy and Clinical Correlations

Shoulder & Axilla: Clinicals - Joint & Axilla Jams

• Shoulder Dislocation:
  • Anterior (>95%): Axillary n. risk (deltoid palsy, regimental badge anesthesia). Arm abducted, ext. rotated.
  • Posterior: Seizures, electrocution. Arm adducted, int. rotated.
• Rotator Cuff (SITS) Tears: Supraspinatus most common. Painful arc (60-120°). Drop arm test.
• Adhesive Capsulitis (Frozen Shoulder): Diffuse pain, ↓ active & passive ROM.
• Axillary Nerve Injury: Due to shoulder dislocation or surgical neck humerus fracture.
• Long Thoracic Nerve Injury (C5,6,7): Winging of scapula. (📌 "C5,6,7 keep the wings to heaven")
• Axillary Lymphadenopathy: Infection or malignancy (e.g., breast cancer mets).

  ⭐ In anterior shoulder dislocation, the humeral head often lies subcoracoid. Axillary nerve vulnerability is key.

Brachial Plexus: Injuries - Nerve Network Nightmares

• Upper Trunk (C5, C6) - Erb-Duchenne Palsy
  • Cause: ↑ neck-shoulder angle (birth, falls).
  • Sign: "Waiter's tip" hand: arm adducted, medially rotated; forearm extended, pronated.
  • Muscles: Deltoid, supraspinatus, infraspinatus, biceps.
  • 📌 ERB's: Elbow extended, Rotated arm (medially), Biceps weak.
• Lower Trunk (C8, T1) - Klumpke's Palsy
  • Cause: Hyperabduction of arm (e.g., grabbing branch).
  • Sign: Claw hand (intrinsic muscle paralysis).

  ⭐ Often with Horner's syndrome (ptosis, miosis, anhydrosis) if T1 sympathetic fibers involved.

• Long Thoracic N. (C5,C6,C7) Injury
  • Cause: Mastectomy, stab.
  • Sign: Winging of scapula (serratus anterior palsy).
• Axillary N. (C5,C6) Injury
  • Cause: Shoulder dislocation, humerus surgical neck fracture.
  • Sign: Deltoid paralysis (abduction 15-90° loss); regimental badge anesthesia.

Elbow & Forearm: Clinicals - Twists & Traps

• Elbow Joint:

  • Tennis Elbow (Lat. Epicondylitis): ECRB. Pain: resisted wrist extension.
  • Golfer's Elbow (Med. Epicondylitis): Common flexor origin. Pain: resisted wrist flexion.
  • Olecranon Bursitis (Student's): Bursa inflammation.
  • Pulled Elbow (Nursemaid's): Radial head subluxation. Children < 5 yrs. Reduce: supination + flexion.

• Nerve Entrapments:

  • Cubital Tunnel (Ulnar N.): At elbow. Sensory: medial 1.5 fingers. Motor: hypothenar, interossei. Froment's.

    ⭐ Ulnar Paradox: Proximal lesion → less clawing (FDP paralysis) vs. distal.

  • Pronator Syndrome (Median N.): By pronator teres. Forearm pain. No night symptoms.
  • AIN Syndrome (Median N. motor): "OK" sign weak (FPL, FDP I/II). No sensory loss.
  • PIN Syndrome (Radial N. motor): Arcade of Frohse. Finger/wrist drop. No sensory loss.

• Fractures/Dislocations:

  • Supracondylar Fx (Humerus): Children. Risk: Brachial A., Median N. → Volkmann's.
  • Elbow Dislocation: Posterior common. Risk: Ulnar N.
  • Forearm Fx: 📌 MUGR: Monteggia-Ulna fx (proximal) + radial head disloc.; Galeazzi-Radius fx (distal) + DRUJ disloc.

Wrist & Hand: Clinicals - Grip Grievances

• Power Grip Impairment:
  • Ulnar N. injury: Weakness of interossei, hypothenars. Positive Froment's sign (IPJ flexion of thumb via FPL).
  • Median N. injury: Affects thenar eminence, FDS, lateral FDP.
• Precision Grip Impairment:
  • Median N. injury: Loss of opposition (Ape hand deformity), weak pinch. AIN syndrome: "OK" sign weakness.
  • Ulnar N. injury: Affects adductor pollicis, interossei; difficulty with key grip.
• Common Causes:
  • Carpal Tunnel Syndrome (CTS): Median N. compression; nocturnal paresthesia, thenar atrophy. Positive Phalen's/Tinel's.
  • De Quervain's Tenosynovitis: APL & EPB inflammation; radial wrist pain. Positive Finkelstein's test.
  • Trigger Finger: Flexor tendon stenosing tenosynovitis; locking/catching.

⭐ Froment's sign (ulnar N. palsy): thumb IPJ flexion via FPL (median N.) compensates for weak adductor pollicis during pinch grip tests an ulnar nerve lesion effectively testing the adductor pollicis muscle..

High‑Yield Points - ⚡ Biggest Takeaways

• Erb's palsy (C5-C6) results in waiter's tip deformity.
• Klumpke's palsy (C8-T1) causes total claw hand.
• Radial nerve injury leads to wrist drop (e.g., Saturday night palsy).
• Median nerve compression in carpal tunnel causes ape thumb deformity.
• Long thoracic nerve injury results in winged scapula.
• Supracondylar humerus fracture risks median nerve and brachial artery injury.
• Scaphoid fracture presents with anatomical snuffbox tenderness and avascular necrosis risk.