Juvenile kyphosis in pigs. A spontaneous model of Scheuermann's kyphosis.

The development of kyphotic lesions in pigs with different weights from herds with a high frequency of the lesion was analysed pathologically, radiologically, and for alkaline phosphatase, calcium, magnesium, and phosphate in blood samples. The development of kyphosis was caused by the formation of ventral hemivertebrae due to the absence of ventral vertebral epiphyseal centres of ossification. Within the ventral parts of affected vertebral epiphyses, the retained chondroid tissue was dysplastic and the contents of cartilage canals with vessels often clotted with fibrin were reduced. As lesions such as fractures and inflammation that may be a secondary cause of kyphosis in pigs were absent and all blood parameters were within normal range, secondary causes of the condition, including metabolic disturbances, were excluded. It can be seen that the present type of porcine kyphosis does not develop until later in life as the ossification centres within the epiphyses of vertebrae have a retarded appearance. As the present porcine type of kyphosis pathomorphologically is comparable with Scheuermann's kyphosis in man, it constitutes a spontaneous model for this common cause of structural kyphosis of the thoracic or thoracolumbar spine.