Aetiology, pathophysiology

Question 1

Lau VJ 2013

Rads and CT monitor MCD from 6wo until euthanasia in 14 Labs
Definitive dx of MCD based on necropsy and microCT

Answer 1

Frequency of MCD was 50%

CT more sensitive for early MCD - earliest signs at 14WO!!

Necropsy and microCT showed that MCD manifested as a lesion only of the SUBCHONDRAL BONE in dogs <18WO

Changes within subchondral bone precede articular cartilage fissures/fracture

Question 2

Lau VJ 2013

Purpose bred MCD-prone Labs
Serial evaluation of MCP in Lab puppies with and without DED
Rads, CT, necrospy, microCT, histology

Answer 2

MicroCT proved absence of secondary COO in pups

MicroCT or histology did not find radiographic evidence of trochlear sclerosis at 15-27WO in Labs with and without MCD (thus negative findings does not r/o MCD!)

MCD was initiated in CALCIFYING zone of articular cartilage
–At 15wo, localised disturbance in endochondral ossification (delayed calcification in calcifying zone) -> propagates to cleft -> DJD
–Retained hyaline cartilage within coronoid fragment ultimately ossifies during maturation of MCP –> weak points that crack between subchondral bone and retained cartilage

Question 3

Lau VCOT 2015

Prospective
6-17wo Pups with and without MCD
Rads, CT

Answer 3

All pups developed MCD but had normal skeletal development - and absence of RUI, confirmed on necropsy