Ch 55 - Carpus, metacarpus and digits Flashcards
What is the “radiocarpal” bone actually called…
Intermedioradial carpal bone
What is the tiny bone proximal to C1?
Sesamoid of the abductor pollicus longus
How many carpal bones are there?
Seven
- Intermedioradial carpal bone
- Ulnar carpal bone
- Accessory carpal bone
- C1-4
What kind of joint is the carpus?
Ginglymus (hinge) joint
What is the articular disc of the carpus?
The radioulnar ligament
How are the metacarpophalangeal sesamoids numbered?
2 sesamoids per metacarpophalangeal joint, numbered 1-8 from medial to lateral
Where are the metacarpal physes located?
When do they fuse?
- MC1 proximally
- MCII-V distally
- Fuse by 5-6m
What are the intermetacarpal joints?
Joints betweent the proximal ends of the adjacent metacarpals.
- Synovial membrane from the carpometacarpal joints contributes
- Distal to carpometacarpal joint, metacarpal bones are united for a variable distance by fibrous tissue known as interosseous metacarpal ligaments
List some anatomical differences of the cat manus
- Absense of a straight medial collateral ligament
- Dogs lack a dorsal elastic ligament attachment to the head of the middle phalanx, and the shape of the head is different from that of the cat and therefore dogs cannot retract their claws like cats do
How is joint motion often graphed?
Joint angle vs % gait cycle
What palmar ligaments have the highest elastic modulus?
How do the palmar ligaments tend to fail?
Acessorometacarpal ligaments
Modes of failure:
- 58.3% mid-ligament
- 22.9% avulsion fracture
- 18.8% at bone-ligament interface
What is a proposed mechanism of nontraumatic fractures of the intermedioradial carpal bone?
Incomplete fusion of the centres of ossification
- Can be bilateral
- Boxers, Eng SpSp, Setters, Pointers overrepresented
What form of intermedioradial carpal bone fractures are seen in Greyhounds?
What are the treatment options?
Oblique midbody fractures of the right limb
- Lag screw
- Headless self-compressing cannulated screw
- K-wires
- Excision of fragments
- External coaptation (incomplete or nondisplaced)
What are the types of accessory carpal bone fracture?
- Type I (67%): Avulsion of distal margin at articular surface. Attached of ligament to ulnar carpal bone. Ia palmarolateral, Ib palmaromedial
- Type II (13%): Proximal margin of the articular surface. Attachment of ligaments to distal radius and ulna
- Type III (3%): Avulsion of distal surface at palmar end. Attach to MC IV and V
- Type IV (12%): Avulsion at insertion of flexor carpi ulnaris at caudoproximal surface
- Type V (5%): comminuted
What are the guidelines for deciding if MC/MT fractures require surgery?
- More than 2 MC/MTs fractured in same manus
- Fractures involving both the primary weight bearing bones
- Articular
- Displaced by over 50%
- Involve the base of MC/MT II/V (collateral attachment)
- Large-breed or athletic/working dog
No study has demonstrated that any for of treatment if better than any other