Dyschondroplasias, including osteochondrosis, in boars between 25 and 169 days of age: histologic changes.

Microscopic sections of physeal and articular-epiphyseal (A-E) cartilages from major limb bones of 60 boars between 25 and 169 days of age were examined. The objectives in this study were to determine the age of onset and pathogenesis of osteochondrosis, a defect of endochondral ossification. Lesions regarded as typical of osteochondrosis were associated with physes of pigs from 25 days of age, indicating an earlier age of onset than has generally been documented. Two morphologically distinct lesions were observed, but both had areas with increased depth of the zone of hypertrophying chondrocytes. Some lesions were repairing. With increasing age of the pigs, the number of involved physes increased in each of 6 different age groups up to 169 days. Lesions associated with physes were observed in boars younger than those with lesions associated with A-E complexes. A few pigs at, or older than, 53 days of age, had osteochondrosis-like lesions involving epiphyseal growth cartilages. However, a dyschondroplasia different from osteochondrosis and typified by chondrolysis was more frequently associated with A-E complexes of pigs at or greater than 79 days of age. The number of affected cartilages and sites with this type of lesion also increased with age. Although osteoarthrosis had not developed in any of the pigs, it is probable that chondrolytic areas were precursors of degenerative joint disease. To date, osteochondrosis has been used to encompass lesions involving physes and A-E complexes. However, in view of the findings in the present study, dyschondroplasia is the preferred term to be used generically and then qualified by morphologic description, since causations may be different.

Dyschondroplasias, including osteochondrosis, in boars between 25 and 169 days of age: radiologic changes.

Boars in 6 different groups (between 25 and 169 days of age) were examined radiographically to determine the age of onset of lesions associated with the sites of endochondral ossification in limb bones. Although lesions were in histopathologic sections of physes from all groups of pigs, they were not found frequently in radiographs of live animals until boars were more than 100 days old. Microscopic lesions were infrequent in articular-epiphyseal (A-E) complexes of pigs less than 80 days old, and radiographic examination of live animals had limited value until animals were greater than 100 days old. Radiographs of slabs of bone were useful in the detection of physes with lesions in all age groups and A-E complexes with lesions in boars 100 days of age or older. So that the accuracy of radiographic examination of live animals for the diagnosis of dyschondroplasias could be evaluated, a comparison was made between the numbers of growth cartilages with lesions as determined by radiologic examination of live animals, radiographic examination of slabs of bone, and light microscopy (examination of tissue sections). Only 21% of the lesions associated with physes and 22% of the lesions associated with A-E complexes were detected in radiographs of bones of live pigs. The authors concluded that the latter method was inaccurate for the identification of dyschondroplastic foci. Identification of lesions by examination of radiographs of slabs of bone was only slightly more accurate, since 33% of physes and 23% of A-E complexes which had lesions were found. Potential errors in evaluation of radiographs were discussed.(ABSTRACT TRUNCATED AT 250 WORDS)