Morphological studies of front limb deformities in lambs.

Long bones of 16 3- to 6-month-old lambs with bowed forelimbs underwent radiologic, microradiographic and histologic examinations. The distal ends of the radii showed a combination of valgus, flexion and internal rotation. There were thin cortical bone and large marrow cavity adjacent to the growth plate in the radii and metacarpi. Histological studies showed increased numbers of osteoclasts adjacent to the zone of calcified cartilage of the growth plate. The trabeculae of primary and secondary spongiosa were fewer and thinner than those of controls. The length of secondary spongiosa were greatly reduced and the lateral compaction of the metaphysis was defective. The growth plate was normal. The predominant finding was osteoporosis resulting from increased osteoclastic resorption of bone trabeculae.