Observations on growth plates in limbs of foals
Brown, M.P.; MacCallum, F.J.
Veterinary Record 98(22): 443-446
1976
ISSN/ISBN: 0042-4900 PMID: 936460 Document Number: 100755
Epiphysitis, which is related to growth plate irregularities, can cause enlarged, painful metaphyses and limb deviation. In the present study, bones of 26 clinically normal crossbred foals (quarter horse, Belgian, Percheron and other cold-blooded breeds), aged 52-104 days were examined by oxytetracycline labelling, radiography and sectioning. Many of the growth plates showed irregularities; 18 foals had an undulating growth plate in the third metatarsal bone (Mt III). In this bone, the cartilage was often wider and discoloured at the foci of fusion, and sometimes there were spicules of bone growing out from the epiphyseal side, or projections of bone embedded in the cartilage. However, at other fusion sites, such as between distal epiphyses of ulna and radius, there was a thinning of the cartilage, and no spicules. The foci of fusion in Mt III occur at the points of greatest compression owing to the animal's weight, so the spicules at these sites may be normal structures associated with points of compression. However, they may represent abnormal fusion, during which cartilage at fusion points is obliterated, so that continuing endochondral ossification in adjacent cartilage "stretches" the area and causes the bony spicules to form, or the projections of bone to become embedded in the cartilage. "Islands" of bone were also seen embedded in the growth plate. Enlargement of peripheral margins of metaphysis and epiphysis near the growth plate was noted in Mt III and metacarpal III, but was apparently unrelated to fusion. In the epiphysis of the radius, blood vessels were growing out towards the metaphysis. Blood samples showed normal ranges for serum Ca, P and alkaline phosphatase.