Osteochondrosis

Question 1

definition of osteochondrosis

Answer 1

multifocal disorder of epiphyseal (growth) cartilage that occurs in both the articular-epiphyseal cartilage complex (immature joint cartilage covering the ends of growing long bones) and the growth plate (physis) in humans and in a variety of animal species

Question 2

what suggests that pathophysiology is essentially the same in all species

Answer 2

among all species examined, the early (subclinical) lesions in the articular-epiphyseal cartilage complex are remarkably similar, as are those in the growth plate

Question 3

epiphyseal (growth) cartilage

Answer 3

• vascular hyaline cartilage
• destined to ossify by endochondral ossification, becoming bone in the mature individual
• composed to 4 morphologically and biochemically distinct zones (resting, proliferating, hypertrophic, calcifying)

Question 4

endochondral ossification

Answer 4

• orderly maturation of cells in the four zones is required
• cartilage calcification followed by vascular invasion
• osteoprogenitor cells produce osteoid on calcified cartilage matrix
• epiphyseal cartilage must be viable for process to occur

Question 5

why can underlying lesions of osteochondrosis only occur in growing individuals

Answer 5

because epiphyseal cartilage is absent in the adult –> may see clinical signs in adulthood

Question 6

cartilage vascular supply

Answer 6

• articular cartilage is avascular

- epiphyseal cartilage is supplied by blood vessels within cartilage canals

Question 7

cartilage canals

Answer 7

• channels containing blood vessels, nerves, lymphatics
• arise mainly from perichondrium
• some arise from subchondral bone
• present at birth, gradually decrease in number and extent
• disappear completely by several months of age

Question 8

chondrification of cartilage canals

Answer 8

• physiological process
• lumens of cartilage canal vessels fill with cartilage
• not associated with pathological changes in epiphyseal cartilage

Question 9

epiphyseal cartilage v adult articular cartilage

Answer 9

• viability of epiphyseal cartilage highly dependent on blood supply
• adult articular cartilage derives almost all nutrition from synovial fluid, minor supply from vessels in subchondral bone

Question 10

morphology of lesions of OC

Answer 10

in both articular-epiphyseal complex and growth plate, lesions of osteochondrosis are composed of focal areas of retained cartilage that are not converted to bone by endochondral ossification

Question 11

A-E complex lesions (info)

Answer 11

• earliest lesion composed of focal areas of necrotic epiphyseal cartilage that often is centered on a necrotic cartilage canal blood vessel
• in more chronic lesions, areas of necrosis causes delay in endochondral ossification and marked reduction in subajacent bone

Question 12

healing of A-E complex lesions

Answer 12

• early lesions may heal completely by gradual incorporation of the necrotic cartilage into the subchondral epiphyseal bone
• cleft formation may occur, leading to cartilage flap formation and subsequent osteoarthrosis

Question 13

etiology of osteochondrosis

Answer 13

• trauma
• hereditary factors
• rapid growth
• nutritional factors
• ischemia

Question 14

trauma in osteochondrosis

Answer 14

• most widely proposed etiology
• appearance of chronic lesions
• some predilection sites in areas of increased biomechanical stress
• pigs: medial condyle (weight-bearing forces), housing on hard floor

Question 15

how to reduce clinical disease and why

Answer 15

the great majority of subclinical lesions of OC heal; therefore, if the joint can be protected from trauma during the time frame during which it is vulnerable, it is possible that clinical disease could be reduced

Question 16

genetic factors

Answer 16

• familial in humans
• prevalence high in all domestic pigs
• large breed dogs

Question 17

rapid growth

Answer 17

• OC occurs during the period of rapid growth
• most commonly affected species are those in which rapid growth is emphasized
• prevalence of lesions not altered significantly by reducing growth rate by restricting feeding/breeding animals with fast growth rates with those with slower growth rates

Question 18

nutritional factors

Answer 18

• dietary manipulations have been unsuccessful in reducing incidence/severity of disease
• Cu deficiency produces OC-like lesions in horses (generalized, not multifocal)

Question 19

ischemia

Answer 19

• early lesions of OC in A-E complex in pigs and horses associated with abnormalities in cartilage canal blood vessels
• femoral condyles of pigs: lesions of cartilage necrosis first seen in first areas of epiphyseal cartilage to become avascular (axial aspect of condyles) and are associated with necrotic blood vessels