Osteochondrosis (OCD) Pathophysiology

Question 1

define osteochondrosis

Answer 1

a disturbance or abnormality of endochondral ossification that may lead to secondary arthritis and is commonly found in diarthrodial (freely moveable with a joint capsule and synovial fluid) joints (shoulder and elbow, stifle and hock)

Question 2

describe the etiology of osteochondrosis

Answer 2

multifactorial:
1. genetics: rapid growth rate/weight gain, breed dispositions to this
2. biomechanical factors or local physiological trauma

Question 3

describe the pathogenesis/progression of osteochondrosis (7)

Answer 3

1. necrotic cartilage: was meant to be normal bone but for some reason didn’t make it and now stuck as this necrotic gross cartilage
2. lack of ossification (didn’t convert to bone)
3. cartilage retention
4. thick and weak cartilage
5. may form a cleft (flap, dissecans lesion)
6. OC fragment formation
7. clinical signs develop

Question 4

describe common sites of osteochondrosis in the dog (6) and the horse (5) and why are these common locations?

Answer 4

dog: humeral head, femoral condyle, trochlear ridge of talus, and also femoral head, patella, and distal radius

horse: distal intermediate ridge of the tibia, trochlear ridges of the talus, trochlear ridges of the femur, and also humeral head and glenoid of scapula

why: pressure causes OCs to form in same place every time and build up

Question 5

describe the prognosis of osteochondrosis

Answer 5

favorable for: younger horses when it’s in the hock or the fetlock with discrete fragments

deserving attention/unfavorable: stifle with large OC, stifle cysts, fetlock dissecans lesions

Question 6

what are the 3 types of OC?

Answer 6

1. Type I: dissecans: lifting/dissecting lesion near the center of a convex joint surface
2. Type II: fragments!
3. subchondral bone cysts: infolding of articular cartilage into the underlying cancellous bone

Question 7

what are the 2 most important clinical signs of OC?

Answer 7

1. joint effusion (swelling)
2. inconsistent lameness, especially with subchondrondal bone cysts

Question 8

describe radiology/diagnostics for OC (4)

Answer 8

1. always radiograph when see an effusive joint!
2. consider a bilateral study!
3. interpret in light of clinical signs
4. consider ultrasound or nuclear scintigraphy

Question 9

what are 3 non-surgical treatments of OC?

Answer 9

1. exercise modification
2. pain management
3. intra-articular medication

Question 10

describe surgical treatment of OC

Answer 10

1. removal of defective cartilage
2. exposure of healthy vascular subchondral bone via debridement or curettage
3. arthroscopy to do all this; is the gold standard

Question 11

describe surgical treatment of SBCs

Answer 11

1. intralesional corticosteroid injection: favorable outcomes but may require repetition
2. transcortical screw: gives stability and bone stimulation

Question 12

describe post-operative care of OC (3)

Answer 12

1. rest and rehab
2. systemic medications: glycosaminoglycans
3. intra-articular medications: hyaluronate, AVOID corticosteroids