Osteochondrosis Flashcards
What is the definition of osteochondrosis?
-
Defect in endochondral ossification
- Endochondral ossification = the process by which epiphyseal cartilage becomes bone
- Non-inflammatory cause of arthritis
What are the different regions of growing bone?
- Diaphysis
- Metaphysis
- Physis
- Epiphysis
Long bone growth occurs from the ________ and the ________.
growth plate; epiphysis
What is the relative contribution of the physis and epiphysis to bone length?
The growth plate is responsible for ~80% of the length; the epiphysis provides the other ~20% (though this can vary between bones and species)
T/F: Most of the bone growth occurs by 12mo
FALSE
Most of the bone growth occurs by 26wks, or ~6mo
When does the epiphysis usually ossify by?
At the end of ~6mo, the epiphyses have ossified though the growth plates are still open
Endohondral ossification occurs in both locations but it is the second that is the issue in OCD
Explain the terms “center of ossification” and “ossification wave”
- Center of ossification = section of epiphysis where endochondral ossification begins
- Ossification wave = ossification travels outward and anastomosis continues
Describe the transfer of blood supply to the epiphysis from the perichondral plexis to the metaphysis
- Cartilage blood supply: perichondral plexis
- Blood supply to metaphysis comes from medullary canal
- Ossification wave: anastomoses form
- Perichondral plexis
- Epiphyseal bone supply
How can an error/interruption during the transfer of blood supply during bone growth lead to thicker epiphyseal cartilage?
- Small defects may ossify by other means
- Intramembranous ossification
- Lesion resolves, not a clinical problem
- Failure to ossify–> thickened cartilage
- Thickened cartilage acts as ‘stress riser’
- Necrosis–> cleft between cartilage and bone
- Focused stresses over cleft–> fracture of cartilage
How can thickened epiphyseal cartilage become a flap of cartilage at the joint surface?
- Too much breakdown –> ischemia and necrosis of cartilage
- Because endochondral ossification is not progressing normally in this area–> thicker cartilage (failure of endochondral ossification)
- If bigger area, might persist as growth continues
- Might still undergo intramembranous ossification as bone continues to mature
- Fissure can develop between bone and cartilage
- If fissure extends to the joint surface, it results in a flap of thickened cartilage –> osteochondrosis dissecans (OCD)
How can a fissure between the thickened cartilage and subchondral bone trigger DJD?
- Necrotic cartilage induces repair
- Inflammation is first stage of repair
- Defect in joint surface accelerates DJD
What is the etiology of OCD?
Multifactorial
- Genetics/heredity
- Non-genetic/environmental factors
- Nutrition
- Vitamin D
- Ca
- Energy
- Trauma
- Nutrition
- Both genetic and non-genetic factors must be present for disease to manifest
What are the breed and gender dispositions of OCD?
Males predisposed
Large/giant breed dogs
What is the significance of heritability in OCD?
Heritability 10-45%
DON’T BREED
What is the relationship between dietary Ca and vitamin D levels and OCD?
- High vit D/Ca promotes errors in endochondral ossification in Great Danes
- Direct causation of OCD not established
- High Ca/vit D linked to other ortho diseases
What radiographic findings are compatible with OCD?
Flattening contour of the joint
