Upper Limb: Wrist and Hand

Upper Limb > Wrist and Hand > Study Aims
STUDY AIMS
At the end of your study, you should be able to:
Describe the radiocarpal joint, its movements, and supporting ligaments
Know the bones of the hand and their organization
Describe the movements at the carpometacarpal, metacarpophalangeal, and interphalangeal joints
Describe the organization of the deep fascia of the hand
Understand the arrangement of the intrinsic muscles of the hand

Upper Limb > Wrist and Hand > Guides
GUIDE

6-5: Upper Limb: Wrist and Hand
    Wrist (Radiocarpal) Joint (Plate 453)
  • Biaxial synovial joint
    • Located at a line joining the styloid processes of the radius and ulna
    • Articulation of distal end of radius and articular disc of radioulnar joint with the proximal row of carpal bones (except the pisiform)
    • Fibrous capsule surrounds the wrist
      • From distal ends of radius and ulna to proximal row of carpal bones
      • Lined by a synovial membrane with numerous folds
    • Movements
      • Flexion/extension
      • Abduction/adduction (radial/ulnar abduction)
      • Circumduction
      • Adduction greater than adduction
    • Ligaments (Plate 454 and Plate 455)
      • Dorsal and palmar radiocarpal ligaments from the radius to the two rows of carpals on the palmar and dorsal sides
      • Ulnar collateral ligament from the ulnar styloid process to the triquetrum
      • Radial styloid ligament from the radial styloid process to the scaphoid
    • Blood supply: Branches of the dorsal and palmar carpal arches
    • Nerve supply
      • Anterior interosseous branch of median nerve
      • Posterior interosseous branch of radial nerve
      • Dorsal and deep branches of ulnar nerve
    Hand
  • Bones (27) (Plate 456 and Plate 457) ( Fig. 6-5-1)
    • Carpal bones (bones of the wrist or carpus)
      • Proximal row: Scaphoid, lunate, triquetrum, pisiform,
      • Distal row: Trapezium, trapezoid, capitate, hamate
    • Metacarpals (5) consist of
      • Base (proximal)—articulate with distal row of carpal bones
      • Body
      • Head (distal)—articulate with proximal phalanges and form knuckles
    • Phalanges (14)
      • Each digit has three phalanges: proximal, middle, and distal, except for
      • Thumb (has two)
      • Each phalanx has a base (proximal), body, and head (distal)
      • Decrease in size from proximal to distal
    Major Joints of the Hand (Plate 458)
  • Carpometacarpal, metacarpophalangeal, and interphalangeal are all synovial joints supplied by branches of adjacent vessels and nerves
  • Intercarpal joints
    • Joints between carpal bones of first row and joints between carpal bones of second row
    • Midcarpal joint between first and second rows
    • Supported by anterior, posterior, and interosseous ligaments
    • Function as a single unit
    • Small gliding movements between carpal bones
  • Carpometacarpal joints
    • Plane type synovial joints, except for carpometacarpal of thumb (saddle type)
    • Medial four carpometacarpal joints in one fibrous joint capsule
    • Separate capsule for thumb
    • Joint for thumb between the trapezium and first metacarpal
      • Allows flexion, extension, abduction, adduction, circumduction, and opposition
      • Loose joint capsule allows for free movement
  • Metacarpophalangeal joints (MCP)
    • Heads of metacarpals articulate with base of proximal phalanx
    • Deep transverse metacarpal ligaments hold heads of metacarpals 2 through 5 together
    • Separate joint capsule for each joint
    • Movements: flexion, extension, abduction, and adduction.
    • Because the collateral ligaments tighten during flexion, abduction, and adduction are only possible in the extended position
  • Interphalangeal joints
    • Proximal interphalangeal joint = PIP
    • Distal interphalangeal joint = DIP
    • Allow flexion and extension
    Fascia of the Hand ( Plate 459)
  • Extensor and flexor retinaculum continuous with antebrachial fascia
  • Palmar fascia thickened centrally as the palmar aponeurosis
    • Four distinct extensions to the bases of the fingers
    • Continuous with the fibrous tendon sheaths
    • Anchored tightly to skin of palm by numerous ligamentous bands (retinacula cutis)
  • Fibrous digital sheaths surround synovial sheaths that enclose superficial and deep flexor tendons
  • Medial fibrous septum extends from medial border of palmar aponeurosis to fifth metacarpal
  • Lateral fibrous septum extends from lateral border of palmar aponeurosis to third metacarpal
  • Septa create compartments within the palm
    Muscles of the Hand (Plate 465 and Plate 469) (Table 6-5-1)
  • Adductor pollicis
  • Thenar (lateral) compartment
    • Abductor pollicis brevis
    • Flexor pollicis brevis
    • Opponens pollicis
  • Hypothenar (medial) compartment
    • Abductor digiti minimi
    • Flexor digiti minimi brevis
    • Opponens digiti minimi
  • Short muscles of the hand
    • Lumbricals—unusual in that they flex MCP joints and extend IP joints
    • Palmar interossei—adduct digits
    • Dorsal interossei—abduct digits
  • Palmaris brevis
    • Wrinkles skin of hypothenar eminence
    • Improves palmar grip
Upper Limb > Wrist and Hand > Figures
FIGURES
Plate 454: Upper Limb—Wrist and Hand—Ligaments of Wrist
Plate 455: Upper Limb—Wrist and Hand—Ligaments of Wrist continued )
Fig. 6-5-1: Transverse section through the carpus showing the carpal tunnel and its contents. (From Gosling JA, Harris PF, Whitmore I, et al. Human Anatomy, 4th Editon. Mosby, 2005, p. 119, Fig. 3.98)
Upper Limb > Wrist and Hand > Tables
TABLES

Table 6-5-1: Intrinsic Hand Muscles
Muscle Origin Insertion Innervation Action Blood Supply
Abductor pollicis brevis** Flexor retinaculum, tubercles of scaphoid and trapezium Lateral side of base of proximal phalanx of thumb (1st digit) Recurrent branch of median nerve (C8,T1) Abducts and assists in opposition of thumb Superficial palmar branch of radial artery
Flexor pollicis brevis** Flexor retinaculum and trapezium Lateral side of base of proximal phalanx of thumb Recurrent branch of median nerve (C8,T1) Flexes proximal phalanx of thumb Superficial palmar branch of radial artery
Opponens pollicis** Flexor retinaculum and trapezium Lateral side of 1st metacarpal Recurrent branch of median nerve (C8,T1) Draws 1st metacarpal forward and rotates it medially Superficial palmar branch of radial artery
Adductor pollicis Oblique head—bases of second and third metacarpals capitate and adjacent bones; Transverse head—anterior surface of third metacarpal Medial side of base of proximal phalanx of thumb Deep branch of ulnar nerve (C8,T1) Adducts thumb Deep palmar arch
Palmaris brevis Palmar aponeurosis Skin of ulnar border of palm Superficial palmar branch of ulnar nerve (C8) Deepens the hollow of the hand Superficial palmar arch
Abductor digiti minimi* (hand) Pisiform bone, tendon of flexor carpi ulnaris Medial side of base of proximal phalanx of little finger Deep branch of ulnar nerve (C8,T1) Abducts the little finger (fifth digit) Deep palmar branch of ulnar artery
Flexor digiti minimi brevis* (hand) Flexor retinaculum and hook of hamate bone Medial side of base of proximal phalanx of little finger Deep branch of ulnar nerve (C8,T1) Flexes proximal phalanx of the little finger Deep palmar branch of ulnar artery
Opponens digiti minimi* Flexor retinaculum and hook of hamate bone Medial side of fifth metacarpal Deep branch of ulnar nerve (C8,T1) Draws fifth metacarpal anteriorly and rotates it to face thumb Deep palmar branch of ulnar artery
Lumbricals 1 and 2 Lateral two tendons of flexor digitorum profundus Lateral sides of extensor expansion of digits 2 and 3 Median nerve (C8,T1) Extends digits at interphalangeal joints and flexes metacarpophalangeal joints Superficial and deep palmar arches
Lumbricals 3 and 4 Medial three tendons of flexor digitorum profundus Lateral sides of extensor expansion of digits 4 and 5 Deep branch of ulnar nerve (C8, T1) Extends digits at interphalangeal joints and flexes metacarpophalangeal joints Superficial and deep palmar arches
Dorsal interossei 1–4† Adjacent sides of two metacarpal bones Base of proximal phalanx and extensor expansion of digits 2–4 Deep branch of ulnar nerve (C8,T1) Abducts digits from axial line of hand—third digit Deep palmar arch
Palmar interossei 1–4‡ Palmar surfaces of metacarpals 2, 4, and 5 Bases of proximal phalanx and extensor expansion of digits 2, 4, and 5 Deep branch of ulnar nerve (C8,T1) Adducts digits toward axial line of hand—third digit Deep palmar arch
*Muscles located in the hypothenar compartment of the hand
**Muscles located in the thenar compartment of the hand
Bipennate muscles
Unipennate muscles: remembering DAB (Dorsal interossei ABduct) and PAD (Palmar interossei ADduct) can help you figure out where these muscles insert
(Modified from Moses KP, Banks JC, Nava PB, et al. Atlas of Clinical Gross Anatomy. Mosby, 2005, p. 281, Table 24.1).

Upper Limb > Wrist and Hand > Facts and Hints
FACTS & HINTS

PART A: HIGH-YIELD FACTS
Box 6-5-1: Anatomic Points
Arterial Arches of the Hand
  • Superficial palmar arch
    • Formed from main terminal branch of ulnar artery
      • Enters hand between hook of hamate and pisiform bone
      • Superficial to flexor retinaculum
      • Divides into superficial palmar arch and deep branch of ulnar artery
    • Gives rise to three common palmar digital arteries
      • Anatomose with palmar metacarpal arteries
      • Gives rise to two proper palmar digital arteries to sides of digits 2 through 4
  • Deep palmar arch
    • Formed from terminal branch of radial artery
      • Passes from anatomical snuff box on dorsum of hand
      • Runs between heads of first dorsal interosseus muscle to reach palm
    • Anastomoses with deep branch of ulnar artery
    • Gives off three palmar metacarpal arteries (anastomose with common palmar digital arteries from superficial arch)
    • Gives off princeps pollicis artery to supply palmar surface and lateral sides of thumb
    Anatomical Snuff Box
  • Depression on posterolateral wrist
  • Visible when thumb is fully extended
  • Bounded anteriorly by tendons of the abductor pollicis longus and extensor pollicis brevis
  • Bounded posteriorly by tendon of the extensor pollicis longus
  • Structures in floor of snuff box
    • Radial artery
    • Radial styloid process proximally
    • Base of first metacarpal distally
    • Scaphoid and trapezium between radial styloid and first metacarpal
    Box 6-5-2: Clinical Points
    Colles' Fracture
  • Complete transverse fracture within the distal 2 cm of the radius
  • Distal fragment displaced dorsally, giving the classic “dinner fork deformity”
  • Ulnar styloid may also be avulsed
  • Results from forced dorsiflexion of the hand, such as in breaking a fall with an outstretched, pronated hand
  • Most common fracture in adults older than 50 years old
  • Seen most frequently in elderly women
  • Healing usually good as the bone has a rich blood supply
  • Box 6-5-3: Clinical Points
    Scaphoid Fracture
  • Scaphoid is the most commonly fractured bone of the carpus
  • Proximal pole of the bone has a poor blood supply and as a result, fracture may take several months to heal
  • This increases risk of avascular necrosis and subsequent degenerative joint disease at the wrist
  • Fracture often difficult to spot on initial radiographs, which should be repeated at 2 to 3 weeks in any patient presenting with a severely sprained wrist
  • Box 6-5-4: Clinical Points
    Dupuytren's Contracture
  • Progressive fibronodular thickening of the palmar fascia
  • Leads to fixed flexion deformity of the fingers (most commonly the fourth and fifth digits)
  • Condition often bilateral and usually affects middle-aged males of Northern European decent, suggesting hereditary predisposition
  • Risk factors include alcohol, liver disease, and antiepileptic medication
  • Treatment is surgical

  • PART B: MNEMONICS
    Box 6-5-5: Memory Aids
  • Carpal bones (lateral to medial): Some Lovers Try Positions That They Can't Handle
  • PROXIMAL ROW
    Some Scaphoid
    Lovers Lunate
    Try Triquetral
    Positions Pisiform
    DISTAL ROW
    That Trapezium (“Trapezium over the thumb”)
    They Trapezoid
    Can’t Capitate
    Handle Hamate
    Note: If you forget if you're starting at the lateral or medial side of each row, remember that the Scaphoid is in the anatomical snuffbox and the trapez iUM is at the base of the th UMB.
    Box 6-5-6: Memory Aids
  • Flexor carpi superficialis and profundus insertions: Superficialis splits the two, to permit profundus to pass through (see Plate 464)
  • Interossei muscles: Palmar interossei ADduct the digits (PAD)
    Dorsal interossei ABduct the digits (DAB)

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