Part 4 - Carpal Tunnel & Hand

• Carpal tunnel

  Boundaries:

  Anterior (roof): Flexor retinaculum (transverse carpal ligament) attached to Pisiform and hook of hamate medially, Scaphoid and tubercle of trapezium laterally

  Posterior: Carpal bones

  Contents:

  Flexor pollicis longus, Flexor carpi radialis, Median nerve, Anterior interosseus artery, Tendons of flexor digitorum superficialis AND profundus, Ulnar and radial bursa

  
• Carpal tunnel syndrome


  • From pressure on median nerve at this site, Affects distal nerve distribution

  
• Ulnar Tunnel/Canal


  Boundaries:

  Anteriorly (roof)- palmar carpal ligament

  Posteriorly (floor)- flexor retinaculum

  Medially- pisiform

  Laterally- hook of hamate

  Contents:

  Ulnar nerve, Ulnar artery, Ulnar vein

  
• Anatomical Snuff Box


  Space at the lateral side of the wrist, visible with the full extension of the thumb

  Boundaries:

  Medially- extensor pollicis longus

  Laterally- abductor pollicis longus and extensor pollicis brevis

  Proximal- styloid process of radius

  Deeply - scaphoid

  Contents:

  Radial artery, Cephalic vein (origin), Radial nerve- superficial branch crosses

  
• Colle's fracture


  Most common forearm fracture, Complete transverse fracture of the radius (the distal 2cm completely separates)
• Carpal Bones


  • Proximal row (with time of ossification) lateral to medial: Scaphoid (4-5 years), Lunate (4 years), Triquetrum (3 years), Pisiform (10-12 years)

  Distal row (with time of ossification) lateral to medial: Trapezium (4-5 years), Trapezoid (4-5 years), Capitate (2 months), Hamate (3 months)

  
• Fascia of the palm

  Continuous with the antebrachial fascia of the forearm and the fascia of the dorsum of the hand, Thin over the thenar and hypothenar eminences, Forms a thickened palmar aponeurosis centrally, In the digits it forms digital sheaths, Continuous with the flexor retinaculum, When palmaris longus is present, palmar aponeurosis forms the tendon of palmaris longus

  
• Compartments of the palm

  • Hypothenar- medial, Thenar- lateral, Central- middle, Adductor- deepest muscular plane, Interosseous- between metacarpal bones, Potential spaces- between the tendons and the deep fascia, thenar and midpalmar spaces are separated by the lateral fibrous septum

  
• Palmar aponeurosis


  Strong, well-defined part of the deep fascia of the palm; thickest in the middle, Extends from the flexor retinaculum (with which it is continuous) to the base of the 2nd to 5th fingers, Medial fibrous septum- extends deeply from medial border to 5th metacarpal, Lateral fibrous septum- extends deeply from lateral border to 3rd metacarpal, Functions: Channeling of tendons and neurovascular bundles, Transmission of loads, Anchorage of skin, Binding role for deep transverse metacarpal ligaments, Limiting role of thumb joint motion, Lubrication of flexor tendon sheaths, Muscular attachments, Vascular protection and pumping action for return of venous blood

  
• Thenar muscles (acting on the thumb)


  • Adductor pollicis, Abductor pollicis brevis, Flexor pollicis brevis, Opponens pollicis

  
• Hypothenar muscles (act on little finger)

  • Opponens digiti minimi, Flexor digiti minimi brevis, Abductor digiti minimi, Palmaris brevis

  
• Metacarpal muscles


  • Lumbricals, Dorsal interossei, Palmar interossei

  
• Lumbricals


  1st and 2nd innervated by median nerve, 3rd and 4th innervated by deep branch of ulnar nerve, Flex metacarpophalangeal joints and extend interphalangeal joints of 2nd to 5th digits

  
• Dorsal interossei


  1st to 4th innervated by deep branch of ulnar nerve, Abduct fingers and adduct thumb
• Palmar interossei


  1st to 3rd innervated by deep branch of ulnar nerve, Adduct fingers

  
• Superficial palmar arch


  Origin- ulnar artery deep to palmar aponeurosis, Completed on its lateral side by superficial palmar branch from radial artery, Gives rise to 3 common palmar digital arteries

  
• Deep palmar arch


  Origin- radial artery, Completed by deep palmar branch from ulnar artery, Gives rise to 3 palmar metacarpal arteries, Princeps pollicis artery, Radialis indicis artery

  
• Dorsal carpal arch


  Origin- radial and ulnar arteries, Arches within fascia on dorsum of hand

  
• Venous drainage


  Superficial and deep venous palmar arches drain into deep veins of forearm, Dorsal digital veins drain into 3 dorsal metacarpal veins, Cephalic vein- arises from lateral side of dorsal venous network, Basilic vein- arises from medial side of dorsal venous network

  
• Nerve branches of the hand

  • Recurrent (thenar) branch of median nerve, Lateral branch of median nerve, Medial branch of median nerve

  
• cis artery


  Radialis indicis artery
• Dorsal carpal arch


  • Origin- radial and ulnar arteries
  • Arches within fascia on dorsum of hand

  
• Venous drainage


  • Superficial and deep venous palmar arches drain into deep veins of forearm
  • Dorsal digital veins drain into 3 dorsal metacarpal veins
  • Dorsal metacarpal veins unite to form dorsal venous network
  • Cephalic vein- arises from lateral side of dorsal venous network
  • Basilic vein- arises from medial side of dorsal venous network

  
• Nerve branches of the hand

  1. Branch

  2. Origin

  3. Structures innervated

  
• Intercarpal joints


  • Plane type synovial joints
  • Articulation: Between carpal bones of proximal row, Between carpal bones of distal row, Midcarpal joint- between proximal and distal rows, Pisotriquetral joint- pisiform and palmar surface of triquetrum
  • joint capsule: continuous common articular cavity with carpometacarpal joints, except carpometacarpal joint of thumb, fibrous layer- surrounds intercarpal joints and unites carpals, synovial membrane- lines fibrous layer and attached to margins of articulating surfaces of carpals
  • Ligaments: Carpals are united by anterior, posterior and interosseous ligaments
  • Movements: Mostly small movements, Proximal row more movable than distal row, Flexion and extension of hand initiated at midcarpal joint, Extension and abduction occur at midcarpal joint, Flexion and adduction occur mainly at the wrist joint
  • Blood supply: Dorsal and palmar carpal arches
  • Innervation: Anterior interosseous branch of median n., Dorsal and deep branches of ulnar n.
• Carpometacarpal and intermetacarpal joints

  • All plane type synovial joints except carpometacarpal joint of thumb (saddle type synovial joint)
  • Articulations: Distal surfaces of distal row of carpals with carpal surfaces of bases of metacarpals, At thumb- trapezium with base of 1st metacarpal (having separate articular cavity), Intermetacarpal joints- radial and ulnar aspects of bases of metacarpals
  • Joint capsule: 4 medial carpometacarpal joints and 3 intermetacarpal joints enclosed by a common capsule on palmar and dorsal surface, Common synovial membrane lines the internal surface of the fibrous layer of the joint capsule, Fibrous layer of carpometacarpal joint of the thumb surrounds the joint and is attached to the margins of the articular surfaces
  • Ligaments: Palmar and dorsal carpometacarpal ligaments, Palmar and dorsal intermetacarpal ligaments, Interosseous intermetacarpal ligaments, Superficial and deep transverse metacarpal ligaments
  • Movements: Carpometacarpal joint of the thumb allows angular movements in any plane and restricted axial rotation, allows opposition of thumb, Carpometacarpal joints of 2nd and 3rd digits- no movement, Carpometacarpal joint of 4th digit- slightly mobile, Carpometacarpal joint of 5th digit- moderately mobile
  • Blood supply: Peri-articular arterial anastomoses of wrist and hand, Dorsal and palmar carpal arches, deep palmar arch and metacarpal arteries
  • Innervation: Anterior interosseous branch of median n., Posterior interosseous branch of radial n., Deep and dorsal branches of ulnar n.
• Metacarpophalangeal and interphalangeal joints

  • MP joints- condyloid synovial type, IP joint- hinge synovial type
  • Articulations: MP- heads of metacarpals with bases of proximal phalanges, IP- heads of phalanges with bases of the more distal phalanges
  • Joint capsule: Encloses each MP and IP joint with a synovial membrane lining a fibrous layer that is attached to the margins of each joint
  • Ligaments: Each joint capsule is strengthened by a medial and lateral collateral ligament, These 2 ligaments have 2 parts: Denser cord-like parts- pass distally from phalangeal and metacarpal heads to phalangeal bases, Thinner fan-like parts- pass anteriorly and attach to thick, densely fibrous or fibrocartilaginous plate, the palmar ligaments/plates, which form the palmar aspect of the joint capsule
  • Movements: At thumb MP joint- flexion-extension only, 2nd to 5th MP joints- flexion-extension, abduction-adduction, circumduction, At IP joints- flexion-extension only
  • Bloody supply: Deep digital arteries arising from the superficial palmar arches
  • Innervation: Digital nerves arising from the ulnar and median nerves
• Looseness of the capsule facilitates free movement of the thumb
• Limit movement at carpometacarpal and intermetacarpal joints