Developmental diseases of the MSK system

Question 1

What are the 3 locations where endochondral ossification occur postnatally?

Answer 1

Physis:
- Responsible for the majority of longitudinal bone growth
Articular-epiphyseal cartilage complex (AECC):
- Primarily responsible for radial expansion of the epiphysis
Cuboidal bones:
- The majority of these bones ossify from a single centre

Question 2

What is osteochondrosis?

Answer 2

It is a developmental skeletal disorder characterised by focal failures of endochondral ossification that occur in well-defined, species-specific predilection sites in young animals.

Question 3

Define:

• Osteochondritis

- Osteochondritis dissecans

Answer 3

Osteochondritis: extension of lesions to the articular surface causing inflammation of the joint.
Osteochondritis dessecans: presence of a dissecting osteochondral flap

Question 4

How does osteochondrosis occur?

Answer 4

Interruption of the blood supply of a bone, in particular to the epiphysis,followed by localised bony necrosis and later, regrowth of the bone.

Question 5

What are the 3 commons prediction sites (joints) of osteochondrosis on the horse?

Answer 5

Tibiotarsal joint:
- Distal intermediate ridge of the tibia
- Lateral trochlear ridge of the talus
Femoropatellar joint:
- Lateral trochlear ridge of the femur
- Patella 
Fetlock joint

Question 6

What are the 3 common prediction sites of osteochondrosis on the dog?

Answer 6

Shoulder
- Caudal aspect of humeral head
Stifle
- Lateral (& medial) femoral condyle
Elbow
- Coronoid process of the ulna
- Medial condyle of the humerus

Question 7

What are 2 physeal development abnormalities?

Answer 7

• Physeal dysplasia- acquired condition characterised by gross enlargement of the physis due to mismatch of metaphyseal bone strength and loads.
• Angular limb deformaties- deviation of long axis in frontal plane.

Question 8

What are the 2 types of angular limb deformity?

Answer 8

Valgus- limb deviates laterally distal to site of deformity.

Varus- limb deviates medially distal to site of deformity.