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 disatance 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 canot retract their claws as cats cat
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 palmerolateral, 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
How are MC injuries classified in racing Greyhounds?
Which are most commonly fractured?
- Type 1: Endosteal and cortical bone thickening, clinical lame on day of and after the race. Rest for 3m with gradual return
- Type 2: Minimally displaced hairline fractures. External coaptation for 6-8wk
- Type 3: Complete, displaced fractures. Surgery and external coaptation
MCV of left thoracic limb and MCII of right limb most common
A study of 23 dogs, only 4 returned to race in more than 10 races with some success
What is a potential cause of sesamoid disease?
What sesamoids are most commonly effected?
What breeds are predisposed?
- Sesamoids II and VII have significantly fewer vascular foramina on the bones than all other sesamoids
- II and VII most commonly effected
- Greyhounds and Rottweiler overrepresented
Better clincal results and less OA change in those threated conservatively with rest
What is the most common injury of the canine carpus?
Hyperextension
What percentage of athletic dogs with carpal valgus or varus returned to function after treatment with a neoprene brace?
79%
What percentage of shearing injurys are in the forelimb?
27% in the forelimb
- 79% of which are distal
- 69% are medial
- 50% instability
What is the characteristic stance of a dog with flexor tendon laceration?
Hyperextension of the distal interphalangeal joint. When weightbearing, the claw will appear elevated
What is the recommended extension angle for PCA?
10-12 degrees
List the plate options for PCA
- DCP or LC-DCP
- Hybrid-DCP
- Single- or double-stepped hybrid arthrodesis plate (VOI)
- CastLess plate (Orthomed) (20% less risk of MC fracture)
What are recommendation to avoid complications associated with the bone plate in PCA?
- MC screws no more than 40% diameter
- Plate spans more that 50% length of MCIII
- Additional support of IM pins (controversial)
- Ensuring proper alignment of distal limb
- Adequate removal of articular cartilage
How do the CastLess plate screws engage the MCs?
Engage MC III and IV at an angle of 8 degrees
What is the reported radiagraphic healing after PCA?
- 40% with hybrid plate at mean 288d
- 46.2% with CastLess plate at mean 209d
Bony bridging occurs in intercarpal and carpometacarpal joints between 9 and 12 weeks
Radiocarpal joints between 17 and 30 weeks
How much of the carpal joint motion is by the antebrachiocarpal joint?
85%
What is carpal laxity syndrome?
Carpal hyperextension, hyperflexion or flexural deformity in young puppies.
- Dobermans and Shar-Peis overrepresented
- Associated with over or under supplemented diets and concrete floors with little exercise room
- Recovery in 1-4wk with appropriate diet, controlled exercise program and good traction flooring
What are the most common neoplastic digit masses in the dog and cat?
Dog:
- SCC
- melanoma
- STS
- MCT
Cats:
- SCC
- FSA
- Adenocarcinoma
- OSA
- MCT
- HSA
What is the major difference regarding paw pad corns in Greyhounds as apposed to other breeds?
Nearly all lesions will recur in Greyhounds, other breeds do not have recurrence after surgical excision
What is the aetiology of avascular necrosis of the carpal bones?
Unknown!
- Possible trauma, drugs, bone infection
- Reported in intermedioradial carpal bone and accessory carpal bone
- PCA resolved pain and lameness
