MSK TBL 11: Wrist & Hand Functional Anatomy

palmar aponeurosis

• thick, fibrous central fascia

• proximal end [apex] of triangular aponeurosis is continuous w/ flexor retinaculum & palmaris longus tendon

wrist joint

radiocarpal joint

• articulation

  • btwn radius & articular disc & scaphoid, lunate & triquetrum

  • ulna does NOT participate

  • proximal articular surface forms concave surface

    • distal convex surface

• capsule

  • encloses joint & is attched above to distal ends of radius & ulna & below to the proximal row of carpal bones

• synovial membrane

  • lines capsule & is attached to margins of articular surfaces

  • joint cavity does NOT communicate w/ distal radioulnar joint or w/ joint cavities of intercapal joints

• nerve supply

  • anterior interosseous nerve [from median nerve] & deep branch of radial nerve

wrist [radiocarpal] joint ligaments [4]

1. anterior [palmar radiocarpal] ligament

2. posterior [dorsal radiocarpal] ligament

   1. 1&2 strengthen capsule

3. ulnar collateral [medial] ligament

   1. attached to styloid process of ulna & to triquetral bone

4. radial collateral [lateral] ligament

   1. attached to styloid process of radius & to scaphoid bone

movement that’s not possible at wrist joint

rotation not possible [achieved by radioulnar joint]

pronation/supination compensate for this lack of rotation

[flex/extend, ab/aduct, & circumduction possible]

flexors attach to

metacarpal bones

abduction of wrist is performed by which muscles

flexor carpi radialis

extensor carpi radialis longus & brevis

adduction of wrist is performed by which muscles

flexor carpi ulnaris

extensor carpi ulnaris

carpal tunnel

• carpal bones form arch that convex on dorsal side, concave on palmar side

• groove of palmar side called sulcus carpi

  • covered by sheath of tough connective tissue = flexor retinaculum [transverse carpal ligament]

    • attached radially to trapezium & ulnar side to pisiform & hook of hamate

9 flexor tendons passing thru carpal tunnel

• flexor digitorum profundus [4 tendons]

• flexor digitorum superficialis [4 tendons]

• flexor pollicus longus [1 tendon]

in carpal tunnel, median nerve courses btwn

FDP & FDS

which nerve innervates the thenar muscles?

recurrent branch of median nerve

where does median nerve bifurcate?

typically, after nerve exits carpal tunnel

[in 5-10% of pple, happens more proximally]

guyon’s canal

AKA ulnar canal or ulnar tunnel

• space btwn pisiform & hamate

• ulnar artery & ulnar nerve travel thru into hand

anatomical snuffbox borders

• medially: extensor pollicus longus

• laterally: extensor pollicus brevis & abductor pollicis longus

• floor: scaphoid & trapezium

  • radial artery cross these bones as it passes diagonally from anterior surface of radius to dorsal surface of hand

most frequently fractured carpal bone

scaphoid [fracture along waist]

from fall on palm when hand abducted

synovial flexor sheaths

• in hand, tendons of flexor digitorum superficialis & profundus invaginate a common synovial sheath

  • sometimes called ulnar bursa

• medial part extends distally w/o interupption on tendons of little ginger

• lateral part of seath ends on middle of palm

• distal ends of long flexor tendons of index, middle, & ring fingers acquire digital synovial sheaths as they enter the fingers

*pattern of infection spread

Flexor pollicus longus sheath

• FPL has its own synovial sheath that passes into thumb

• sometimes called radial bursa

  • communicates w/ common synovial sheath at level of wrist in 50% of subjects

oblique intertendinous connections

[3]

• linked proximal to MCP joints

• resist independent extension of 4 medial digits

  • esp ring finger

extensor expansion

• on posterior surface of each finger, extensor tendon joins this fascial expansion

  • near PIP joint, splits into 3 parts

    • central part inserted into base of middle phalanx

    • 2 lateral parts converge to insert into base of distal phalanx

palmaris brevis

small superficial muscle over hypothenar eminence

• origin

  • flexor retinaculum & palmar aponeurosis

• insertion

  • skin on medial border of palm of hand

• innervation

  • superficial branch of ulnar nerve

• action

  • corrugates skin of hypothenar eminence to improve grip of palm

fascial spaces of palm: medial fibrous septum

passes from ulnar border of palmar aponeurosis & attchs to anterior border of 5th metacarpal bone

fascial spaces of palm: lateral fibrous septum

passes from lateral border of palmar aponeurosis & attchs to anterior border of 3rd metacarpal bone

fascial spaces of palm: oblique fibrous septum

btwn 1st & 3rd metacarpal

palm of hand is divided into how many compartments?

4

1. medial

2. mid-palmar space

3. thenar space [misnomer]

4. lateral

medial compartment of palm

contains hypothenar muscles

mid-palmar space compartment of palm

• lies btwn medial & oblique fibrous septum

• contains 2nd, 3rd, & 4th lumbrical muscles

• lies posterior to long flexor tendons to middle, ring, & little fingers

• lies superficial to interosseous muscles & the 3rd, 4th, & 5th metacarpal bones

thenar space compartment of palm

• lies btwn oblique & lateral septa

• contains 1st lumbrical muscle

• lies deep to long flexor tendons to index finger & superficial to adductor pollicus

lateral space compartment of palm

contains muscles of thenar

which compartments of palm are closed off from forearm?

thenar & mid-palmar space closed off by carpal tunnel

[distally, continuous w/ appropriate lumbrical canals]

thenar muscles / muscles of thumb [4]

1. abductor pollicis brevis

2. flexor pollicis brevis

3. opponens pollicis

   1. 1-3 median nerve

4. adductor pollicis

   1. ulnar nerve

hypothenar muscles [3]

1. abductor digiti minimi

2. flexor digiti minimi

3. opponens digiti minimi

all innervated by deep branch of ulnar nerve

intrinsic hand muscles

• 4 lumbricals

  • 2 median [1st & 2nd], 2 ulnar [3rd & 4th]

• 3 palmar interossei

  • ulnar

• 4 dorsal interossei

  • ulnar

lumbrical muscles originate from

tendons of flexor digitorum profundus

lumbrical muscles insert onto

extensor expansions of corresponding finger

action of lumbricals

• flexion at MCP joints [not that imp]

• extension of IP joints [v imp!]

  • only extensors of fingers [pretty much]

palmar interossei muscles [3]

act on index, ring, & little fingers

• origin

  • metacarpal of corresponding finger

• insertion

  • proximal phalanx

  • extensor expansion

• innervation

  • deep branch of ulnar nerve

• action

  • adduct at MCP joints

  • flex at MCP joints

  • extend at IP joints

PAD

dorsal interossei muscles [4]

act on index, middle [2 muscles], & ring fingers

• origin

  • 2 heads from adj. sides of 2 metacarpal bones

• insertion

  • side of base of proximal phalanx

  • extensor expansion

• innervation

  • deep branch of ulnar

• action

  • abduct at MCP joints

  • flex at MCP joints

  • extend at IP joints

DAB

FDS attaches to

middle phalanx

FDP attaches to

distal phalanx

5 synovial joints of hand & fingers

1. midcarpal

2. carpometacarpal

3. intermetacarpal

4. metacarpophalangeal [MCP]

5. interphalangeal [IP]

ligaments of MCP joints

• palmar metacarpal ligaments

  • strong w/ some fibrocartilage

• palmar ligaments

  • united by deep transverse metacarpal ligaments, which hold heads of metacarpal bones together

• collateral ligaments

  • on each side of joints

  • taut when joint in flexion

finger pulp space

• deep fascia of pulp of each finger fuses w/ periosteum of terminal phalanx

  • this closes off a fascial compartment known as pulp space

• terminal branch of digital artery runs thru here

• filled w/ fat

blood supply of hand: 3 anastomotic arterial arches from branches of radial & ulnar arteries

1. superficial palmar arterial arch

2. deep palmar arterial arch

3. dorsal carpal arch

collateral circulation of hand: ulnar artery

superficial branch is main supply

collateral circulation of hand: radial artery

dorsal carpal branch is main supply

digit arteries

• from dorsal, deep, & superficial arches

• supply fingers

• every digit gets 4 arteries

  • 2 dorsal digital from dorsal carpal arch

  • 2 proper palmar digital from superficial arterial arch

princeps pollicis

• supplies blood to thumb

• from radial artery

radialis indicis

• supplies blood to index finger

• from radial artery

radial tubercle [Lister’s tubercle]

distal radius prominence on wrist dorsum

• palpate radius dorsum while pt flexes wrist

• lines up w/ 3rd metacarpal

most common carpal dislocation

scapholunate joint or interval