Chapter 87 - Angular Limb Deformities

Question 1

1. What is the definition of an angular limb deformity?

Answer 1

• A conformational deviation of the limb in the frontal plane

Question 2

2. What is a valgus deformity?

Answer 2

• Lateral deviation of the limb

Question 3

4. True/False – Valgus deformities are typically associated with a certain degree of axial rotation, but varus deformities are not.

Answer 3

• False, either type of deviation is usually associated with a certain degree of axial rotation

Question 3

3. What is a varus deformity?

Answer 3

• Medial deviation of the limb

Question 3

5. (Varus/valgus) deformities are often associated with outward rotation (splay foot)

Answer 3

• Valgus

Question 4

6. (Varus/valgus) deformities are often associated with inward rotation (pidgeon toed)

Answer 4

• Varus

Question 5

7. ALD diagnosis is based on what modalities (4)

Answer 5

• Static evaluation
• Dynamic evaluation
• Palpation
• Radiographs

Question 5

9. Why do foals typically have outward rotation of the entire limb? How is this corrected?

Answer 5

• New born foals are weak, thin chested, and long-legged in relation to their size
• With increasing strength and age, the chest fills out and the connecting muscles become stronger, resulting in an inward rotation of the limb

Question 6

8. What positioning is critical for a clinician evaluating an ALD for accurate diagnosis

Answer 6

• Must be perpendicular to the frontal plane of the examined limb

Question 7

10. Why is dynamic evaluation important for catching an ALD?

Answer 7

• Pigeon-toed foals frequently rotate their fetlock joints outward while advancing the limb. This is caused when the joints are not oriented orthogonally to the long axis of the long bones in the frontal plane or parallel to the ground

Question 8

12. At what day of gestation should all cuboidal bones be visible?

Answer 8

• 300 days

Question 8

13. The _____________ is the last ossification center to appear

Answer 8

• Ulnar styloid process

Question 8

11. Starting at _____ days of gestation, ossification centers can be seen at sites such as the distal radial epiphysis, distal tibial epiphysis, , talus, and accessory carpal bones.

Answer 8

• 260 days

Question 9

14. Where in the cuboidal bones does ossification begin?

Answer 9

• In the center, expanding spherically in all directions to the periphery

Question 10

15. What sort of events affecting the mare may jeopardize the intrauterine environment of the foal and result in incomplete cuboidal ossification at the time of birth? (8)

Answer 10

• Prematurity related to shortened gestation
• Abnormal uterine positioning
• Dysmaturity related to placentitis
• Placental insufficiency
• Severe prolonged metabolic diseases (maternal malnutrition)
• Heavy parasite infection
• Colic and shock
• Chemical insults (vaccinations and antihelmintics)
• Thyroid abnormalities

Question 11

16. For radiographic evaluation of incomplete cuboidal ossification, a ______ view of the carpus and a _____ view of the tarsus are indicated.

Answer 11

• Dorsal
• Lateral

Question 12

18. Define Grade II incomplete cuboidal bone ossification

Answer 12

• All the cuboidal bones have some evidence of ossification, the proximal physes of the MCIII /MT III are open

Question 12

17. Define Grade I incomplete cuboidal bone ossification.

Answer 12

• Some cuboidal bones of the carpus and tarsus have no evidence of ossification

Question 13

19. Define Grade III incomplete cuboidal bone ossification

Answer 13

• All cuboidal bones (carpus and tarsus) are ossified, but small and rounded edges are present. Joint spaces are wide and the lateral styloid process and the malleoli are distinctly visible. Proximal physes of MCIII/MTIII are closed.

Question 14

20. Define Grade IV incomplete cuboidal bone ossification

Answer 14

• All criteria of grade 3 are met. Cuboidal bones are shaped like corresponding adult bones and joint spaces have the expected width

Question 15

21. T/F – Incomplete cuboidal bone ossification does not indicate an ALD per se, but uneven loading of the dysmature skeleton can lead to it.

Answer 15

• True

Question 15

24. What ultimately results to tarsal bones if collapse of the cartilage template is left untreated?

Answer 15

• Deformations worsen and eventually the small tarsal bones fuse to a single irregularly shaped bone

Question 16

22. Dysmature cuboidal bones resulting in ossification of abnormal configuration is especially true in the (front/hind) limbs, where weightbearing forces a rapid change in direction during ambulation.

Answer 16

• hind

Question 17

23. What is the gait descriptor of clinically affected foals with crushed tarsal cuboidal bones? They do this gait rather than what standard gait?

Answer 17

• Bunny hop

Question 18

25. Foals with incomplete tarsal ossification and >_____% collapse of the 3rd and central tarsal bones have a poorer prognosis than foals with <_____% collapse, thereby stressing the importance of early recognition and treatment.

Answer 18

- >30% - <30%