134 - Joints of Upper Limb 3. Wrist Complex & Joints of Hand Flashcards
Rows of phalanges in hand
1
2
3
Proximal, middle, distal
Orientation of metacarpal of the thumb
At right angle to other digits
Two nodular bones on thumb metacarpal
Sesamoid bones
Number of phalanges in thumb
Two
Bones forming the proximal row of carpal wrist
(Radius) Scaphoid, lunate, triquetrum, pisiform (last to ossify) (Ulna)
Bones forming the distal row of carpal wrist
Trapezium, trapezoid, capitate (largest & 1st to ossify), hamate (with hook)
Bone forming the floor of the anatomical snuffbox
Scaphoid bone
Example of a sesamoid bone of the wrist
Trapezoid bone
Proximal border of the flexor retinaculum
Corresponds to location of distal wrist crease
Which wrist bone does the ulna sit across from?
Triquetral bone
Largest bone in the wrist
Capitate
Bone likely to break when falling on an outstretched hand
Radius most likely.
Force passes through the capitate, as it is the largest, into radius.
When do carpal bones commence ossification?
After birth
First bone in wrist to ossify?
Capitate
Order of ossification of carpal bones
Starts at capitate, goes in a counterclockwise direction
capitate->hamate->etc
Age at which pisiform ossifies?
~10-13 years.
Last carpal bone to ossify
Pisiform
Orientation of base and head of metacarpals
Base is proximal, head is distal
When do ossification centres of metacarpals fuse?
Early teens
Bones areticular at the wrist
Scaphoid, lunate, radius.
Triquetral bone slides across, articulates with ulan when hand is bent laterally
Midcarpal joint
Where carpal bones articulate with one another.
Joints in the wrist complex
1
2
•2 joints:
- Radiocarpal - ellipsoid
- Intercarpal (midcarpal) - condylar
Movements at the wrist complex 1 2 3 4
•Biaxial movements -flexion/extension -radial/ulnar deviation Circumduction -flexion > extension (F/E) -ulnar deviation > radial (UD/ RD)
Type of joint that radiocarpal joint is
Synovial ellipsoid joint
Shape of radiocarpal joint
Articular surfaces concave in 2 directions
Why is wrist flexion greater than extension?
Posterior radius projects more distally than anterior.
Why is ulnar deviation greater than radial deviation?
Radial stiloid stops movement. Because of radial articulation with scaphoid, lunate
Where are intercarpal joints?
Between proximal & distal carpal row (excluding pisiform)
Aspects of intercarpal joints 1 2 3 4
•‘Functional’ rather than ‘anatomic’ joint
•No single joint capsule – each bone forms separate unit
•Concave-convex surfaces
•Movements generally opposite to wrist :
-extension > than flexion
-radial deviation > ulnar
How do vessels go to carpal bones?
Travel with radiocarpal ligaments
Two groups of radiocarpal ligaments
Palmar
Dorsal
Palmar radiocarpal and ulnarcarpal ligament shape
Oblique bands from distal radius and distal ulnar
Are palmar or dorsal ligaments stronger?
Palmar
Are radiocarpal or ulnarcarpal ligaments stronger?
Radiocarpal
Where do forearm flexor muscles attach distally?
Beyond carpal region, attach to proximal aspects of metacarpals
Only forearm flexor that attaches to a carpal bone
Flexor carpi ulnaris
Proportion of all fractures and dislocations that are of the wrist
6%
Name for fracture of distal radius
Colles’ fracture
Colles’ fracture
Fracture of distal radius.
Distal radius pulled downwards.
Most commonly broken carpal bone
Scaphoid
Most commonly subluxed carpal bone
Lunate.
When is lunate commonly subluxed?
Secondary to ligament (radio-scaphoid-lunate) injury
Bennett’s fracture
Fracture of base of the 1st metacarpal (thumb).
Fracture into the carpometacarpal joint..
Type of joint between 1st metacarpal and trapezium bone
Saddle joint
Dangerous blood supply to scaphoid bone
~30-35% have vascular foramina entering at distal pole of scaphoid. If scaphoid is fractured through the waist of the bone, you can have interrupted blood supply to proximal scaphoid. This leads to avascular necrosis.
Carpal bone - other than the scaphoid - that suffers from avascular encrosis
Lunate. Not really known why
What links metacarpals 2 - 4
Linked by deep transverse metacarpal ligament (all fingers linked, thumb is free)
What does carpometacarpal joint allow?
It is the thumb ‘saddle joint’.
Enables opposition of thumb
Type of joints of metacarpals 2 and 3
Immobile
Type of joints of metacarpals 4 and 5
Hinge joints (flexion/extension)
Why is it important to detect Bennett’s fractures early?
Abductor pollicis longus and adductor pollicis brevis attach to base of 1st metacarpal.
If there is a fracture, these muscles can pull bone apart.
Street fighter’s fracture
Fracture of the 5th metacarpal
Why is it hard to abduct fingers when wrist is flexed?
As you flex, collateral ligaments tighten, making abduction more difficult.
How are wrists immobilised?
In slight flexion at wrist joint and metacarpophalyngeal joint
Type of joints that metacarpophalyngeal joints are
Condyloid joints.
Convex head of metacarpal with concave base of phalanx. Note articular surface of head of metacarpal more extensive than phalanx
Volar plate
Fibrocartilaginous plate expands surface area for articulation in metacarpophalangeal joints - also at interphalangeal joints
Swan neck injury
Hyperextension of finger leads to compensatory flexion
