Histological study of navicular bone disease.
A histological investigation of navicular bones from 8 horses with navicular disease was carried out to investigate the aetiology of the radiological findings. Two of the horses were double labelled with tetracycline before slaughter in order to assess the vitality of the diseased navicular bone. The examinations revealed no evidence of loss of vitality in the diseased bone areas or in surrounding tissues. A very high rate of remodelling indicated by resorption and formation of bone was present in all cases. This was shown microscopically by the high number of osteoclasts and osteoblasts present, osteoid formation and particularly by a high rate of intravital uptake of tetracycline by the bone. The findings are considered to indicate that navicular disease is not primarily caused by ischaemia and subsequent necrosis, but rather is a consequence of increased activation of bone remodelling caused by altered pressure from the deep flexor tendon on the bone and increased load on the caudal part of the foot. This is further supported by the clinical changes seen after alterations occur in the hoof conformation. The disease is, therefore, considered to be reversible and may be alleviated by altering the load on the navicular bone by special shoeing. Only secondary lesions such as adhesions and spur formation render the disease irreversible.
D000818:Animals; D001847:Bone Diseases / Q000473:pathology / Q000662:veterinary*; D002348:Carpal Bones / Q000473:pathology; D005534:Foot Diseases / Q000473:pathology; D005552:Forelimb; D006734:Horse Diseases / Q000473:pathology*; D006736:Horses