The Wrist Complex

Vanita A PatharePG-1

Objectives

• To understand the anatomy of wrist joint.

• To understand the kinetics and kinematics of wrist joint

• To understand the pathomechanics of wrist joint

Function

• Symbol of power

• It control the length tension relationship in multiarticular hand

muscle to allow fine adjustment of grip.

Wrist complex

The wrist (carpus) consists of two compound joints-

1) Radiocarpal joint

2) Midcarpal joint

• Wrist complex- Biaxial

• Extension/ flexion- frontal axis , saggital plane

• Ulnar deviation/radial deviation- anteroposterior axis , frontal

plane.

• Some degree of pronation/ supination at radiocarpal joint.

• Gilford & colleagues proposed that the two joint, rather then

single joint, system of wrist complex

Premittes larger ROM with less exposed articular surface &

tighter joint capsule.

Less tendency for structural pinch

Allows for flatter multijoint surfaces

Radiocarpal joint

1. Radiocarpal joint

Proximally-Radius and Radioulnar disk as part of triangular

fibrocartilage complex (TFCC)

Distally- scaphoid, lunate, and triquetrum.

• Proximal joint-

1. The lateral radial facet ------- scaphoid

2. The medial radial facet ------- lunate; &

3. The Radio ulnar disc (TFCC) ------ triquetrum & lunate

• Pisiform bone------ increases the moment arm of FCU do no

participate in articulation

• Radio carpal joint surface- oblique, angled slightly volarly and

ulnarly.

• Angle of inclination of distal radius – 23 degree (frontal plane)

• Inclination occurs because the radius length (height) is 12 mm

greater on radial side than on the ulnar side.

• Distal radius-tilted 11 degree volarly with posterior radius

slightly longer than volar radius ----incongruency-----F>E,

UD>RD.

• TFCC -> triangular fibrocartilagenous complex

• It includes articular disc with its fibrous attachment which

provide support to distal radio ulnar joint.

• The disc is connected medially via. Two dense fibrous

connective tissue.

Upper lamina- dorsal and volar radioulnar ligaments-ulnar head

and ulnar styloid.

Lower lamina- sheath of extensor carpi ulnaris(ECU) tendon

and the triquetrum, hamate, and base of 5th metacarpal through

fibers from ulnar collateral ligament.

• Originates from firm attachments on medial border of distal radius

& inserts into base of ulna styloid.

• It separates the radiocarpal from the distal radioulnar joint.

• Thickness---roughly 5mm at ulnar side & 2mm thick at radial side.

• Vascular anatomy- only the peripheral 15-20% of TFCC has a blood

supply.

• The TFCC stabilizes the bones in wrist, acts as shock absorption &

enables smooth movements.

• Meniscus homolog is region of irregular connective tissue that

lies within and is part of lower lamina.

• Along its path meniscus homolog has fibres that insert into ulnar

styloid and contribute to the formation of prestyloid recess.

• Scaphoid, lunate, and triquetrum- proximal carpal row.

• Articulates-distal radius.

• Interconnected- 2 ligaments-

1. Scapholunate interosseous ligament

2. Lunotriquetral interosseous ligament

• The curvature of the distal radicarpal joint surface is sharper than

proximal joint surface- sagittal and coronal planes- incongruent.

• Contact between proximal and distal radiocarpal surface- 20%

The radio carpal joint is incongurent. So joint incongurence and

angulation of proximal joint surface result in F>E, UD> RD

• Length of ulna in relation to radius

Ulnar negative variance- short ulna then radius at their distal end

Ulnar positive variance- distal ulna is long then distal radius

With ulnar +ve variance----impingement of TFCC b/w ulna & tq

Long ulna may be present with distal radius fracture.

Short ulna result in abnormal distribution of force---AVN of lunate

(kienbocks)

In axial loading:80% load---(Scaphoid 60% & lunate 40%)20% TFCC

Midcarpal joint structure

• Proximally- scaphoid, lunate and triquetrum

• Distally- trapezium, trapezoid, capitate and hamate

• The midcarpal joint surfaces are complex, with reciprocally

concave-convex configuration.

• Carpals of distal row- moves in fixed unit

• Capitate and hamate- strongly bound together-small amount of

play among them.

• Distal carpal row- 2 degree of freedom-radial/ ulnar deviation

and flexion/extension.

• Articular surfaces of midcarpal joint- range of extension over

flexion & radial deviation over ulnar deviation.

Capsule and ligaments• Enclosed by- strong but somewhat loose capsule & reinforced

by capsular and intracapsular ligament

• Most ligaments that cross the radiocarpal joint also contribute

to stability at midcarpal joint.

• Similarly, muscles of the radiocarpal joint also function at the

midcarpal joint.

• The FCU is the only muscle that crosses he radiocarpal joint-

bones of proximal carpal row.

Ligaments

• Function

1. Articular stability

2. To guide and check motion between and among the carpals.

Ligaments

Extrensic• That connects carpals to radius and ulna

proximally or to the metacarpal distally.• Less stronger.• Vascularized tissue• More likely to fail but also have better

potential for healing.

Intrensic• They interconnect carpal themselves c/d

intercarpal or interosseous ligaments.• More stronger and less stiff than extrensic

ligament.• They are within the synovial lining so

depend on synovial fluid for nutrition.

• Ligaments

Volar ligaments

Dorsal ligaments

• Volar carpal ligaments and dorsal carpal ligaments.

• Volar carpal ligament-> volar extrinsic and volar intrinsic

ligament.

• Volar extrinsic-> radiocarpal and ulnocarpal ligament.

• Volar radiocarpal- 3 bands-> radioscaphocapitate (radiocapitate),

radiolunate ( radiolunotriquetral) & radioscapholunate ligaments.

• Radial collateral ligament- extension of volar radiocarpal ligament

and capsule

• Ulnocarpal ligament complex- TFCC, ulnolunate ligament &

ulnar collateral ligament.

• Volar intrinsic ligament-

1. Scapholunate interosseous ligament- scaphoid stability- stability

of much of wrist

2. Lunotriquetral interosseous ligament- stability between lunate

and triquetrum.

• Dorsal carpal ligaments

1. Dorsal radiocarpal ligament- converges on triquetrum from distal

radius- attaches to lunate and lunotriquetral interosseous ligament.

2. Dorsal intercarpal ligament-horizontally from triquetrum to lunate,

scaphoid and trapezium.

• Both together form a horizontal V -> radiocarpal stability->

scaphoid stabilization during wrist ROM.

Muscles of wrist complex• Volar wrist musculature 6 muscles have tendon crossing volar ascept of wrist-wrist

flexion1. Palmaris longus (PL)2. Flexor carpi radialis (FCR)3. Flexor carpi ulnaris (FCU)4. Flexor digitorium superficialis (FDs)5. Flexor digitorum profundus (FDP)6. Flexor policis longus (FDP) First 3 primary wrist muscle & last 3 flexors of digits-

secondary action of wrist.

Function of Wrist Complex:Movements

1.Motion are unique combination of

Active muscular

Passive ligamentous

Joint reaction forces

2. No muscular force are applied directly on articular bones of

proximal row, only the FCU muscle applies its force via

pisiform to the move distal bone.

Functions• Movements of the radiocarpal and midcarpal joint.

1. Flexion/ Extension

o Scaphoid- greater motion, lunate- least

o Primary movement at proximal c. row following seq. occur

As wrist extension is initiated from full wrist flexion.

o 1.The distal carpal row( tr, tz, c, h) with its MCP glide over fixed proximal

carpal row(s, l,t) during active extension in same direction as the motion of hand.

o When wrist complex reaches to neutral i.e long axis of 3 MCP in line with long

axis of forearm, the ligament spanning the capitate and scaphoid draw both

together into closed pack position.

2.Continued ext. force now move combined unit of dist. C row &

scaphoid on lunate & triquetrum

At 45 degree of extension—the scapholunate interosseous lig. Bring

scaphoid & lunate into closed packed position this unite all

carpals and move as a fixed unit

3. the carpal moves as the unit on distal radius & TFCC at full ext---

all lig taut in close pack position

4.wrist motion from full wrist extension occur in reverse sequence.

Radial n ulnar deviation

• Complex movement

• The proximal carpal row display unique reciprocal motion with

RD/UD

• In RD carpal slide ulnarly on radius

• The carpal motion not only produce deviation of proximal and

distal carpal radially, but simultaneously flexion of proximal

carpal & extension of distal carpal.

• The opposite motion of proximal & distal carpal occur during

ulnar deviation

• During RD/UD the distal carpal once again move as a relatively fixed

unit, although the magnitude of motion b/w the bones of proximal row

may differ.

• Studies have shown that magnitude of scaphoid flexion during

RD( extension during UD) was related to ligamentous laxity. ( female

> male)

• In full RD both radiocarpal & midcarpal joints are in closed pack

position.

• Functional position: 10 flexion, 35 extension

• Fusion is done in 20 ext, 10 UD

Pathomechanics of Wrist Joint

Wrist Instability• Dorsal intercalated segmental instabiity (DISI)

Injury to one or more ligaments attached to scaphoid and lunate-

diminish or remove the synergistic stabilization of the lunate and

scaphoid.

The flexed distal carpals glide dorsally on the lunate and triquetrum-

accentuating extension of the lunate and triquetrum.

This zigzag pattern of the 3 segments ( the scaphoid, the lunate/

triquetrum & the distal carpal row)- know as intercalated segmental

instability

Lunate assumes an extended posture- DISI

VISI• Volar intercalated segmental instability (VISI)

Caused- ligamentous union of lunate and triquetrum is disrupted

through injury.

Usaually- lunate & triquetrum tend to move towards extesion-

scaphoid flex.

When lunate is no longer linked with triquetrum- lunate and

scaphoid fall into flexion- triquetrum and distal carpal row extends.

This ulnar perilunate instability- VISI

SLAC• Scapholunate advanced collapse ( SLAC wirst)

• With subluxation of scaphoid- increase contact pressure in

smaller area.

• With sufficient ligamentous laxity-capitate sublux dorsally off

the extended lunate- migrate into gap between flexed scaphoid

and extended lunate.

• Progressive degeneration problem from untreated DISI –SLAC

wrist.

Kienbocks Disease

•KD( or lunatomalacia) is an idiopathic AVN of carpal lunate which may lead to collapse of the bone & arthritis in advanced stages

•Ulnar –ve variant wrist is common association•Pain, tenderness, swelling, clunk with deviation, dec. ROM, weak grip.

TFCC• Triangular Fibrocartilage Complex (TFCC) Injury

– Etiology

• Occurs through forced hyperextension, falling on outstretched hand

• Violent twist or torque of the wrist

• Often associated w/ sprain of UCL

– Signs and Symptoms

• Pain along ulnar side of wrist, difficulty w/ wrist extension, possible

clicking

• Swelling is possible, not much initially

• Athlete may not report injury immediately

Tenosynovitis

• Tenosynovitis

– Etiology

• Cause of repetitive wrist accelerations and decelerations

• Repetitive overuse of wrist tendons and sheaths

– Signs and Symptoms

• Pain w/ use or pain in passive stretching

• Tenderness and swelling over tendon

Carpal Tunnel Syndrome

• Carpal Tunnel Syndrome

– Etiology

• Compression of median nerve due to inflammation of tendons

and sheaths of carpal tunnel

• Result of repeated wrist flexion or direct trauma to anterior

aspect of wrist

– Signs and Symptoms

• Sensory and motor deficits (tingling, numbness and

paresthesia); weakness in thumb

Colles’ Fracture

• Dorsally displaced fracture of the distal radius generally occuring 2-3

cm proximal to the radiocarpal joint.

• Most common #, seen mainly in middle aged and elderly women.

• FOOSH most likely cause.

• Clinical Evaluation: Pain and swelling in wrist, often gross

deformity in wrist.

Lunate Dislocation

• Dislocation of Lunate Bone

– Etiology

• Forceful hyperextension or fall on outstretched hand

– Signs and Symptoms

• Pain, swelling, and difficulty executing wrist and finger

flexion

• Numbness/paralysis of flexor muscles due to pressure on

median nerve

Scaphoid #

• Scaphoid Fracture

– Etiology

• Caused by force on outstretched hand, compressing scaphoid

between radius and second row of carpal bones

• Often fails to heal due to poor blood supply

– Signs and Symptoms

• Swelling, severe pain in anatomical snuff box

• Presents like wrist sprain

• Pain w/ radial flexion

Hamate #

• Etiology Occurs as a result of a fall or more commonly from contact while

athlete is holding an implement

• Signs and Symptoms Wrist pain and weakness, along w/ point tenderness

Pull of muscular attachment can cause non-union

Wrist Ganglion

• Wrist Ganglion

– Etiology

• Synovial cyst (herniation of joint capsule or synovial sheath of

tendon)

• Generally appears following wrist strain

– Signs and Symptoms

• Appear on back of wrist generally

• Occasional pain w/ lump at site

• Pain increases w/ use

• May feel soft, rubbery or very hard

Perilunate Injury• Perilunate Injuries

• Load applied to hand forcing the wrist into extension and ulnar deviation

• Severe ligament injury necessary to tear the distal row from the lunate to

produce perilunate dislocation

• Dorsal displacement of the carpus may be seen

• Significant swelling common

– Evaluate for compartment syndrome

• If lunate is dislocated, median nerve symptoms may be present

References

• Joint structure and function -Cynthia Norkins• Kinesiology: the mechanics & pathomechanics of human

movement---- Carol A. Oatis