import { HighYieldBox, ExamCheatSheet, Tabs, Tab, ComparisonTable, VivaScenario, ContentSection, SpecialTestCard , MedicalImage} from '@/components/content' # Thumb Examination Thumb examination requires assessment of the three joints (CMC, MCP, IP), ligament stability (especially UCL), and tendon function. Examiners expect you to perform the thumb UCL stress test correctly, recognize CMC osteoarthritis patterns, and understand the significance of Stener lesion. ## Quick Reference One-Pager ## Anatomy **Joints:** - **CMC (Carpometacarpal)**: Saddle joint, most mobile - **MCP (Metacarpophalangeal)**: Condyloid joint - **IP (Interphalangeal)**: Hinge joint **Key Ligaments:** - **UCL (Ulnar Collateral Ligament)**: Primary restraint to radial deviation at MCP - **RCL (Radial Collateral Ligament)**: Less commonly injured - **Volar plate**: Resists hyperextension - **Dorsal capsule**: Resists flexion **Tendons:** - **EPL (Extensor Pollicis Longus)**: Extends IP, third dorsal compartment - **EPB (Extensor Pollicis Brevis)**: Extends MCP, first compartment - **APL (Abductor Pollicis Longus)**: Abducts thumb, first compartment - **FPL (Flexor Pollicis Longus)**: Flexes IP - **Thenar muscles**: APB, opponens, FPB superficial head (median nerve) - **Adductor pollicis**: Ulnar nerve **Stener Lesion:** - UCL avulses and flips SUPERFICIAL to adductor aponeurosis - Aponeurosis lies between ligament ends - cannot heal - Palpable mass at ulnar MCP joint - ALWAYS requires surgical repair - Named after Bertil Stener (1962) ## Clinical Presentation **CMC (Basal Joint) Osteoarthritis:** **Demographics:** - Women more than men (10:1) - Age greater than 50 years - Bilateral common **Symptoms:** - Pain at thumb base with pinch/grip - Difficulty opening jars - Pain with key turning - Progressive weakness **Signs:** - Square hand appearance - Adduction contracture - Prominence at base of thumb (subluxation) - First web space narrowing **Thumb UCL Injury (Gamekeeper's/Skier's Thumb):** **Mechanism:** - Fall on outstretched thumb (ski pole) - Forced radial deviation of MCP - Gamekeeper's = chronic (wringing necks) - Skier's = acute **Symptoms:** - Ulnar thumb pain after injury - Weak pinch grip - Instability with pinch **Signs:** - Swelling at ulnar MCP - Ecchymosis - Palpable mass (Stener lesion) - Laxity with stress testing **Trigger Thumb (A1 Pulley Stenosis):** **Demographics:** - Adults: Middle-aged women - Pediatric: Congenital, presents around age 1-2 **Symptoms:** - Clicking or locking of thumb - Pain at base of thumb (A1 pulley level) - Morning stiffness **Signs:** - Nodule palpable at A1 pulley (volar MCP crease) - Triggering with flexion/extension - May be locked in flexion (severe) ## CMC Joint Examination **Observation:** - Squaring at thumb base (dorsoradial subluxation) - First web space contracture - Thenar wasting (disuse) **Palpation:** - Tenderness at CMC joint - Dorsal osteophytes - Subluxation/instability **Range of Motion:** - Adduction/abduction - Opposition - Circumduction **Function:** - Pinch strength (compare with contralateral) - Grip strength - Key pinch, tip pinch, tripod pinch ## UCL Injury Examination **UCL Testing Technique:** **Extension Position:** - Tests accessory collateral ligament AND UCL proper - If stable in extension, may have partial tear **30° Flexion:** - Relaxes accessory collateral and volar plate - Isolates the UCL proper - More sensitive for UCL tears **Criteria for Complete Tear:** - Greater than 30° total laxity - Greater than 15° more than contralateral - Absent firm endpoint **Always test both positions and compare sides!** ## Tendon Examination **EPL (Extensor Pollicis Longus):** - Test: Place palm flat on table, lift thumb toward ceiling - Palpate tendon on ulnar side of anatomical snuffbox - Rupture: Cannot extend IP joint (may occur post-distal radius fracture) **EPB (Extensor Pollicis Brevis):** - Extends MCP joint of thumb - Part of first dorsal compartment - Test: Extend MCP while resisting **APL (Abductor Pollicis Longus):** - Abducts thumb metacarpal - Part of first dorsal compartment - Forms radial border of snuffbox **FPL (Flexor Pollicis Longus):** - Flexes IP joint - Test: Hold MCP extended, flex IP against resistance - AIN palsy: Weakness of FPL (part of "OK sign" assessment) **FPB (Flexor Pollicis Brevis):** - Flexes MCP joint - Superficial head: Median nerve - Deep head: Ulnar nerve ## Trigger Thumb Assessment **Palpation:** - Nodule at A1 pulley (volar, at MCP crease) - Tenderness at A1 pulley **Active Movement:** - Ask patient to flex and extend thumb - Observe for catching, clicking, or locking - Note if triggering occurs with flexion or extension **Classification (Quinnell):** | Grade | Description | |-------|-------------| | 0 | Normal movement | | I | Uneven movement | | II | Actively correctable locking | | III | Passively correctable locking | | IV | Fixed locked position | **Pediatric Trigger Thumb:** - Usually presents with fixed flexion of IP joint - Notta's nodule palpable - May spontaneously resolve in first year ## Differential Diagnosis ## Summary Presentation ## Examiner Tips