L4: Bones, ligaments and joints of the hand (incl. wrist) Flashcards
bones of the hand
carpals (8)
- 2 rows of 4
metacarpals (5)
- 1st [thumb] to 5th [wee finger]
phalanges (14)
- proximal
- middle *
- distal
carpals
scaphoid
lunate
triquetrum
pisiform
trapezium
trapezoid
capitate
hamate
carpal tunnel
the carpal tunnel is formed by:
carpals: floor, medial and lateral wall
transverse carpal ligament: roof
transverse carpal ligament is aka flexor retiaculum
medial nerve enters hand from forearm by passing through the carpal tunnel
carpal tunnel syndrome
Carpal tunnel syndrome caused by compression of median nerve
Compression of median nerve usually occurs due to increased pressure in carpal tunnel
Causes:
*Injury (swelling)
*Tendon hypertrophy
metacarpals
5 in total
features: base, shaft, head
base articulates with carpals
head articulates with phalanges
thumb = 1, little finger = 5
boxers fracture
inexperienced boxers tend to hook punch
4th and 5th metacarpals are weaker than other and less well supported
they are easily fractures during hoot punches
phalanges
proximal, middle*, distal
* thumb has no middle phalanx
features:
proximal + middle phalanx: base, shaft, head
distal phalanx: base, shaft, tubercle
mallet finger
extensor tendon rupture or avulsion injury leaves distal phalanx in the flexed position
jersey finger
finger caught in jersey
due to momentum of players finger is hyperextended and the flexor tendon is torn
may also avulse a piece of bone
patient no longer able to flex finger
affected finger resides in affected position
wrist joint
complex, involves many joints:
- distal radioulnar joint
- radiocarpal joints
- intercarpal joints
distal radioulnar joint
ulnar head in ulnar notch of radius
synovial pivot joint
allows for supination and pronation of forearm
radiocarpal joint
joint between:
- distal radius/ulnar fibrocartilaginous disc
- proximal row of carpals; scaphoid, lunate, triquetrum
synovial condyloid joint
- on one side, joint capsule attached to distal radius and ulna
- on other side, joint capsule is attached to proximal carpals
radiocarpal joint movements
flexion / extension
radial deviation [abduction] / ulnar deviation[adduction]
circumduction
intercarpal joints
augment range of wrist movements
plane synovial joints
between carpals of a given row e.g. scaphoid and lunate |||
midcarpal joints
between proximal and distal row of carpals
synovial condyloid joints
wrist joint capsule
joint space is mostly continuous between wrist and hand
synovial membrane lines capsule
capsule reinforced by ligaments:
- anterior interosseous ligaments
- posterior interosseous ligaments
wrist joint: strengthened by 6 ligaments
radial collateral ligament
ulnar collateral ligament
palmar ulnocarpal ligament
palmar radiocarpal ligament
dorsal ulnocarpal ligament
dorsal radiocarpal ligament
radial collateral ligament
radial styloid to tubercle of scaphoid
ulnar collateral ligament
ulnar styloid to triquetrum
palmar ulnocarpal ligament
strengthens capsule
palmar radiocarpal ligament
radius to both rows of carpal bones
fibres directed such that hand follows radius during supination of forearm
dorsal ulnocarpal ligament
ulna to triquetrum
dorsal radiocarpal ligament
radius to both rows of carpals
fibres directed such that hand follows radius during pronation
colle’s fracture
typically due to FOOSH
fracture of radius (and sometimes ulna) approx. 2.5cm from distal end
distal radial fragment moves posteriorly and proximally
there is also dislocation of the radioulnar joint distally
dorsal surface of forearm adopts a dinner fork shape
smith’s fracture
fall onto flexed wrist
direct blow to posterior surface of distal forearm
anterior and proximal displacement of distal radial fragment
scaphoid fracture
most vulnerable carpal to fracture
usually due to fall on outstretched arm with hand in abducted position
normal scaphoid anatomy:
-proximal pole
-wait
-distal pole
arterial blood supply VERY important
scaphoid - arterial blood supply
main arterial blood supply: dorsal scaphoid branch of the radial artery
enters scaphoid at the waist, turns proximally to supply 80% of the bone
the waist is the weakest part of the scaphoid. fracture here can interrupt arterial blood from reaching proximal 80% of bone
distal 20-30% supplied by branches from superficial palmar arch
scaphoid - avascular necrosis (AVN)
waist is weakest part of scaphoid, fracture here can interrupt arterial blood supply from reaching proximal 80% of bone
without arterial blood supply [avascular], proximal 80% of bone dies [becomes necrotic] … leading to avascular necrosis [AVN]
where is the scaphoid
'’hitch hiking’’ position
scaphoid at base of hollow made by thumb tendons
scaphoid found in floor of ‘ anatomical snuffbox’’
thumb movements
capable of wide range of movements due to its carpometacarpal joint (synovial, saddle shape)
The thumb CMC joint is the joint most commonly affected by osteoarthritis
The thumbs MCP joint is a synovial hinge joint
Thumbs only IP joint is a synovial hinger joint
movement of the digits 2-5
proximal + distal IP joints:
- abbreviated to PIP + DIP j
- hinger synovial joints
- flexion + extension
MCP joints:
- knuckles
- condyloid synovial joints
- flexion + extension
- abduction + adduction
- circumduction
CMC joint
- plan synovial joint
surface anatomy of wrist + hand
styloid processes of the radius and ulna
anatomical snuffbox - floor
scaphoid proximally
trapezium distally
anatomical snuffbox - boundaries
extensor pollicis longus
extensor pollicis brevis
abductor pollicis longus
