wrist joint

Osteology

overview

· divided into two rows

· S-shaped midcarpal joint between rows

1. distal row

· trapezium, trapezoid, capitate, hamate

· relatively immobile transverse unit

· fit together snugly

· held together by stout interosseous ligaments

· platform for articulation with MCs

2. proximal row

· lunate and triquetrum (and pisiform)

· more mobile

· articulate with radius and TFCC

3. scaphoid

· spans both rows

individual bones

Scaphoid

Proximal surface

· convex articular area for radius

· extends onto dorsal surface

Ulnar surface

· narrow convexity for lunate

· sweeps into concavity for capitate

Distal surface

· triangular convexity for trapezoid and trapezium

Tubercle

· blunt prominence on Palmar Radial Distal surface

· flexor retinaculum attached to it

Waist

· narrow nonarticular area

· between tubercle and capitate-radial articular surfaces

· may have slip of attachment from FCR

Lunate

Distal surface

· cylindrical proximal facet for radius

· extends dorsally

Sides

· facets for scaphoid and triquetral

Proximal surface

· concave facet for capitate

Triquetral

· syn. cuneiform

· distal surface

· articular surface for hamate

· volar surface

· articular facet for pisiform

· radial surface

· articular concavity for lunate

· ulnar surface

· tubercle for attachment of ulnar collateral ligament

· extensor retinaculum attaches to it

Pisiform

· sesamoid in FCU

· articulates with triquetral

· flexor retinaculum attaches to it

· extensor retinaculum attaches to it

· provides mode of attachment of FCU and flexor retinaculum to

· hamate via pisohamate ligament

· base of MC V via pisometacarpal ligament

Trapezium

· forms concave facet with trapezoid for convexity of scaphoid

· saddle-shaped distal articular surface for MC I

· prominent volar ridge for tendon of FCR

· prominent dorsal tubercle for carpometacarpal ligament

Trapezoid

· wedged between trapezium and capitate

· articulates distally with MC II

Capitate

· largest carpal bone

· lies between

· hamate ulnarly

· scaphoid and trapezoid radially

· articulates proximally with lunate

· articulates distally with MC III (and tiny part of MC IV)

Hamate

· articulates distally with MC IV and V

· volar surface projected into hook-like flange

· overhangs ventral concavity of carpus

· flexor retinaculum attached to it

Ligaments

· divided into

· volar and dorsal

· extrinsic and intrinsic

extrinsic ligaments

· from radius to carpus

· from carpus to metacarpals

Volar

Radial collateral ligament

· not a true collateral ligament

· not possible in wrist

· more palmar than lateral

· should be considered as most radial of volar radiocarpal fascicles

Volar radiocarpal ligament

· arranged in superficial and deep layers

Superficial layer

· fibres assume V-shape

Deep layer

· three strong fascicles

1. radioscaphocapitate (or radiocapitate)

· supports waist of scaphoid

2. radiolunate

· supports lunate

3. radioscapholunate

· connects scapholunate articulation with volar distal radius

· acts as checkrein for scaphoid flexion and extension

Ulnocarpal complex (triangular fibrocartilage complex)

· consists of

1. meniscus homologue

· radiotriquetral ligament

· originates from sigmoid notch of radius

· extends toward palm around ulnar border of carpus

· inserts into triquetrum

2. triangular fibrocartilage

· articular disc

· originates from sigmoid notch of radius

· extends horizontally to insert into base of ulnar styloid

· between meniscus and disc is prestyloid recess

3. ulnolunate ligament

· connects volar border of articular disc with lunate

4. ulnar collateral ligament

· not a true collateral ligament

· extends from ulnar styloid to base of 5th MC

5. volar and dorsal radioulnar ligaments

Dorsal

Dorsal radiocarpal ligament

· extends from dorsal lip of radius

· divides into three fascicles which insert on

· lunate

· triquetrum

· scaphoid

intrinsic ligaments

· originate and insert on carpus

Short

· three short intrinsics

· volar

· dorsal

· interosseous

· convert all 4 bones of distal row into one functional unit

Intermediate

· three intermediate intrinsics

· lunate-triquetrum

· scaphoid-lunate

· scaphoid-trapezium

· link 2 bones of proximal row with radial pillar

Long

Volar intercarpal ligament

· called deltoid or V ligament

· stabilises capitate

· extends from capitate neck

· attaches to scaphoid and triquetrum

Dorsal intercarpal ligament

· extends from triquetrum

· attaches to scaphoid and trapezium

Arthrology

Distal radioulnar joint

· between distal radius and ulna

· closed distally from wrist joint by triangular fibrocartilage

wrist joint

Radiocarpal joint

· formed by

· radius and triangular fibrocartilage

· scaphoid, lunate and triquetral

· radius has

· triangular facet for scaphoid

· rectangular facet for lunate

· triquetral adjacent to TFCC

· only makes contact with radius in extreme adduction

Midcarpal joint

· continous S-shaped joint

· between proximal and distal carpal rows

· extends proximally and distally between carpal bones as continuous intercarpal joint

· usually does not communicate with radiocarpal joint

Carpometacarpal joint

· continuous joint

· between distal carpal row and MC II-V

· extends proximally between carpal bones

· commonly communicates with midcarpal joint

Thumb carpometacarpal joint

· separate joint

· surfaces reciprocally saddle-shaped