OCTH 222: Wrist Bony Anatomy and Arthrokinematics

Normal Wrist ROM

- flexion 0-80

- extension 0-70

- Radial Dev 0-20

- Ulnar Dev 30-40

Pronation

turning the palm downward

Supination

movement that turns the palm up

Proximal radioulnar joint (PRUJ)

articulation between head of radius and radial notch of ulna; uniaxial pivot joint that allows for rotation of radius during pronation/supination of forearm

distal radioulnar joint (DRUJ)

articulation between the head of the ulna and the ulnar notch of the radius

Distal radius articulates with the distal ulna at the ulnar

notch

Ulnar notch is a depression on the surface of the distal radius

At the wrist ____ axial load is at the Radius and _____ axial load is at the Ulna

80%; 20%

Colles fracture

distal radius is broken by falling onto an outstretched hand

Most common form of wrist

fracture from FOOSH injury

Distal radius displaced dorsally

Lister's tubercle

Bony landmark marking the separation

between the wrist extensor tendons

(ECRB/L) and the long thumb extensor

(EPL)

- Also acts as a pulley for the extensor pollicis

longus (EPL) tendon

Outer layer of the Wrist Joint Capsule

fibrous and attaches to radius, ulna and carpal bones

Inner layer of the Wrist Joint Capsule

synovial membrane secreting synovial fluid to lubricate the joint

Radiocarpal Joint

Articulation between distal radius and the carpus

Joint type: Condyloid joint

Arthrokinematics: Convex-on-Concave

Bones involved: Distal radius, Scaphoid and

Lunate

The Distal ulna does NOT directly articulate with the carpus because it connects to the carpus via a fibrocartilaginous wafer called the:

Triangular disk

midcarpal joint

Articulation between the proximal and distal carpal rows

Convex-on-concave joint mechanics

Joint type: Condyloid joint

intercarpal joints

between adjacent carpals within each row

In wrist flexion and extension, the radiocarpal joint contributes ____% of the movement and the midcarpal joint contributes ___% of the movement

50%;50%

If a patient had surgery to remove the proximal carpal row, how much ROM should they expect to regain after surgery?

About half

Ulnar deviation

Carpal rows roll ulnarly and side radially

Radiocarpal joint motion > midcarpal joint motion

Radial deviation

More limited than ulnar deviation due

to presence of the radial styloid

- Carpal rows roll radially and side ulnarly

- Midcarpal joint motion > radiocarpal joint motion

Dorsal intercarpal ligament

Courses horizontally from triquetrum to lunate, scaphoid, and trapezium

Work together to form a lateral V shape diagonally across the dorsal wrist connecting the

radius, scaphoid and triquetrum

Provides dorsal stabilization to the carpus, especially the scaphoid

dorsal radiocarpal ligament

Connects radius to posterior scaphoid and lunate

Work together to form a lateral V shape diagonally across the dorsal wrist connecting the radius, scaphoid and triquetrum

Provides dorsal stabilization to the carpus, especially the scaphoid

palmar radiocarpal ligament

ligament running from the anterior surface of the distal radius to the anterior surface of the carpal bones

Thick 'sling-like' ligament complex that covers almost the entire volar joint capsules of the

radiocarpal and midcarpal joints

Tightens in wrist extension

radial collateral ligament

Connects scaphoid to radial styloid

Limits ulnar deviation

ulnar collateral ligament

Connects triquetrum to ulnar styloid

Limits radial deviation

Palmar radiocarpal ligaments are much ________ and _________ than its dorsal counterpart

thicker; stronger

proximal row of carpals

No direct tendon attachments

• Acts as an intercalated segment

• Highly mobile → prone to instability

lateral to medial: scaphoid, lunate, triquetrum, pisiform

distal row of carpals

Strong ligamentous connections

• Moves as a rigid unit

• Provides stability for grip and load transfer

Includes: Trapezium, Trapezoid, Capitate, Hamate

Intrinsic Interosseous Wrist Ligaments

Wrist ligaments that ORIGINATE and ATTACH to the carpus

Key ligaments: Scapolunate (SL) ligament and Lunotriquetral (LT ligament

Proximal row carpal bones exhibit more ______________ compared to the

distal carpal row.

intercarpal motion

The _______ carpal row functions more as a single kinematic

unit.

distal

Proximal interosseous carpal ligaments are ______ prone to injury

more

Scapholunate (SL) ligament

connects scaphoid and lunate

Dorsal fibers more important

Lunotriquetral (LT) ligament

connects lunate and triquetrum

Volar fibers more important

In radial deviation, what occurs within the proximal carpal row?

Scaphoid flexes and Triquetrum extends

In ulnar deviation, what occurs within the proximal carpal row?

Scaphoid extends and Triquetrum flexes

Scapholunate (SL) dissociation

FOOSH resulting in SL ligament tear

Lunate follows triquetrum into extension

Capitate collapses into the empty space between the scaphoid and lunate

Scapholunate advanced collapse (SLAC) wrist \

Results in dorsally displaced lunate

Dorsal Ganglion Cyst

Aka the "Bible bump"

Multifactorial pathogenesis: tissue stress, degeneration, underlying joint conditions

Originate from the dorsal wrist joint capsule fibers or dorsal fibers of the SL ligament

Presentation: Dorsal wrist pain when weightbearing in wrist extension

Triangular Fibtrocartilage Complex (TFCC)

Complex of ligaments and fibrocartilage that occupies the

space between the distal ulna and the carpus

What are the 2 primary functions of the TFCC?

1. Main stabilizer of the DRUJ

2. Absorbs impact from axial load

through the distal ulna

What are the 4 key components if the TFCC?

Triangular disk

Radioulnar ligaments (volar and dorsal)

Ulnocarpal ligaments

Extensor carpi ulnaris (ECU) tendon sheath

Extensor carpi ulnaris (ECU) tendon sheath

This fibro-osseous sheath blends its fibers with the TFCC fibers providing dynamic stabilization to the TFCC

Traingular Articular Disc

The TFC portion of the

TFCC

Avascular

Looks like a 'trampoline'

Radioulnar Ligami

Function like the reins of a horse-drawn

carriage to stabilize the DRUJ

Which position is more unstable for the

TFCC? Pronation or supination?

Pronation

TFCC Tear

Due to the complexity of the TFCC and nearby ulnar wrist structures, the ulnar wrist is commonly referred to as the "black box of the wrist".

Mechanism of injury:

Trauma on the ulnar side of the wrist through fall or

weightbearing

Presentation and management:

- Ulnar-sided wrist pain exacerbated by weightbearing on

extended wrist or forearm rotation

- Diagnosis is made through a combination of clinical exams

and imaging

- Surgery is recommended for unstable traumatic tears

- Splinting and therapy is recommended for painful but stable

tears

Scaphoid

carpal bone, closest to the radius, the "some" in the acronym Some Lovers Try Positions That They Can't Handle

Lunate

carpal bone that's shaped like a crescent moon, "lovers" in the acronym Some Lovers Try Positions That They Can't Handle

Triquetrum

the "try" in the acronym Some Lovers Try Positions That They Can't Handle, Pisiform is often attached to this carpal bone

Pisiform

Pea-shaped bone often shown attached to the triquetrum

Trapezium

carpal bone that is closest to the the thumb, the "that" in the acronym Some Lovers Try Positions That They Can't Handle

Trapezoid

thumb side of the hand, "they" in the acronym Some Lovers Try Positions That They Can't Handle

Capitate

carpal bone, the "capital" in the center of the hand, "can't" in the acronym Some Lovers Try Positions That They Can't Handle

Hamate

carpal bone towards the pinky side, has a projection that sort of looks like a ham bone

Radius

lateral bone of the forearm, in line with the thumb

Distal radius

insertion of pronator quadratus

Radial head

articulates with capitulum of humerus, proximal

radial styloid process

the pointed structure at the distal end of the radius

Ulna

Inner and larger bone of the forearm, attached to the wrist and located on the side of the little finger.

Ulnar styloid process

distal pointed projection; located medial to the head of the ulna

Ulnar head

distal end of ulna