Chapter 95 - Carpus

Question 1

1. What are the 3 joints of the carpus?

Answer 1

• Antebrachiocarpal/radiocarpal
• Middle carpal joint
• Carpometacarpal joint

Question 2

2. Which of the 3 carpal joints (always) communicate with each other in the horse?

Answer 2

• Middle carpal and Carpometacarpal joints

Question 3

3. Inadvertent puncture of the carpometacarpal (and subsequently middle carpal) joint may occur when performing what?

Answer 3

• Regional anesthesia of the proximal metacarpal region

Question 4

4. T/F: Analgesia of the radiocarpal and middle carpal joints is selective and specific.

Answer 4

• False, it is not selective (diffusion occurred in 84% -96% of tested limbs)

Question 5

7. What are the 3 bones of the distal row of carpal bones?

Answer 5

• 2nd carpal bone
• 3rd carpal bone
• 4th carpal bone

Question 6

5. What bones make up the carpus? (11 +/-1)

Answer 6

• Radius
• Radiocarpal bone
• Intermediate carpal bone
• Ulnar carpal bone
• 2nd carpal bone
• 3rd carpal bone
• 4th carpal bone
• Accessory carpal bone
• MC3
• MC4
• MC2

Question 7

6. What are the 3 bones of the proximal row of carpal bones?

Answer 7

• Radiocarpal bone
• Intermediate carpal bone
• Ulnar carpal bone

Question 8

8. Which vestigial carpal bone is more likely to be present, 1st or 5th?

Answer 8

• 1st

Question 9

9. What soft tissue structures maintain the orientation of the carpal bones relative to themselves? (4)

Answer 9

• Intercarpal ligaments
• Collateral ligaments
• Fibrous joint capsule
• Palmar carpal ligaments

Question 10

10. The _________ and ________ tendons (and their sheaths) span the carpus dorsally and dorsolaterally, respectively.

Answer 10

• Extensor carpi radialis
• Common digital extensor tendon

Question 11

11. The extensor carpi radialis and common digital extensor tendons are maintained in position over the dorsal surface of the carpus by ____________ which is located _____________.

Answer 11

• Extensor retinaculum
• At the level of the physeal scar

Question 12

12. The carpal extensor retinaculum is located where on the distal radius?

Answer 12

• At the level of the physeal scar

Question 13

13. What two tendons are located on the lateral aspect of the carpus (not dorsal or dorsolateral)?

Answer 13

• Lateral digital extensor tendon
• Ulnaris lateralis

Question 14

14. What structures are found within the carpal canal? (5)

Answer 14

• SDFT
• DDFT
• Median artery
• Median nerve
• Accessory ligament of the SDFT

Question 15

17. Injury to the carpus most often effects which two joints?

Answer 15

• Radiocarpal
• Middle carpal

Question 15

15. What flexor tendon and its sheath is located outside of the carpal canal? For what procedure is it an important surgical landmark?

Answer 15

• Flexor carpi radialis
• For desmotomy of the proximal check ligament (ALSDFT)

Question 16

16. What is the function of the bony and ligamentous structures of the carpus?

Answer 16

• Dissipate axial loading during weight bearing

Question 17

19. High energy injuries to the carpus (falls, kicks, etc.) cause what kind of failure? The resultant injury often results in ___________ and________.

Answer 17

• Acute single load failure
• Open or comminuted fractures
• Carpal instability

Question 18

18. Injury of the middle carpal joint in racing breeds (with exception of external trauma) nearly always involves the ________ aspect of the joint, specifically the _________, _________, and ________.

Answer 18

• Medial
• Radial facet of the 3rd carpal bone
• Distal aspect of the radial carpal bone
• Medial aspect of the distal intermediate carpal bone

Question 19

20. Single load injuries (including luxations of one or more carpal joints) are (more/less) common than those developing because of repetitive loading.

Answer 19

• Less common than repetitive injury

Question 20

22. What is the most common injury to the intercarpal ligaments?

Answer 20

• Injury of the palmar medial intercarpal ligament

Question 20

21. Osteochondral fragmentation of the distal radial carpal and proximal third carpal bones is associated with __________________ caused by repetitive loading. Why does fragmentation of these bones result in a poor athletic soundness prognosis?

Answer 20

• Subchondral bone damage
• They are prone to reinjury following fragment removal, resulting in subsequent joint deterioration from cartilage debris and subchondral bone failure

Question 21

23. What injury to the carpus is associated with anesthetic recovery?

Answer 21

• Injuries to the palmar aspect of the carpus, (hyperextension and hyperflexion of the carpus during recovery)

Question 22

25. Offset carpi have been associated with what type of lameness?

Answer 22

• Lameness within the fetlock joint

Question 23

24. What palmar carpal structure injuries man result in lameness? (5)

Answer 23

- SDFT - DDFT - Fracture of the palmar aspect of cuboidal bones - Fracture of accessory carpal bone - Exostoses of the caudal aspect of the distalradius

Question 24

26. A study has demonstrated a protective effect of (mild)carpal valgus for what?

Answer 24

- Carpal injury