Chapter 73 OCD

Question 1

Name 4 (most common) sites of OCD lesions in dogs and 2 in cats

Answer 1

Dogs:

• Medial humeral condyle
• Humeral head
• Medial and lateral talar ridge (usually medial, Rotties lateral)
• Femoral condyles (med or lat, ?lat more common)

Cats:

• Lateral femoral condyle
• Caudocentral humeral head

Question 2

OCD sex predisposition?

Answer 2

Male (except talus = female)

Question 3

What is the proportion of growth from physis vs epiphysis?

Answer 3

75% physis, 25% epiphysis

Question 4

What are the three stages of OCD?

Answer 4

• Osteochondrosis latens* (early, microscopic lesion)
• Osteochondrosis manifesta* (macroscopically and radiographically apparent)
• Osteochondrosis dissscans* (cartilage flap present, usually clinical signs)

Question 5

What are the four zones of endochondral ossification?

Answer 5

Resting zone

Proliferation zone

Hypertrophic zone

Mineralisation zone

Question 6

What is Heuter-Volkman law?

Answer 6

Growth retarded by compression accelerated by reduced loading (ie more growth when recumbent)

Question 7

Name of “thing” limiting circumferential expansion of growth plate:

Answer 7

Ring of Lacroix

Question 8

Briefly describe the progression from chondrocytes to mature bone:

Answer 8

• Chondrocytes in mineralization zone secrete/maintain mineralized matrix
• Chondrocytes apoptose, removed by clasts.
• Metaphyseal vasculature and osteoprogenitor cells invade empty lacunae.
• Osteoblasts lay down woven bone (primary spongiosa)
• Calcified cartilage and woven bone replaced by lamellar bone.

Question 9

Outline the zones of mature articular cartilage:

Answer 9

• Superficial zone
• Tranzitional zone
• Radial zone
• “Tidemark” (separates uncalcified radial zone and zone of calcified cartilage)
• Calcified cartilage zone
• (Subchondral bone)

Question 10

List reparative and restorative techniques for OCD

Answer 10

(Palliative = fragment removal + lavage)

Reparative:

1. Abrasion
2. Curettage
3. Micropick
4. Forage
5. Spongialization

Restorative:

1. Fragment re-attachment
2. Osteochondral transplant
3. Synthetic osteochondral re-surfacing