Bone Disorders in Animals

Most bone disorders in animals occur secondary to trauma. Less common causes of bone disorders include metabolic abnormalities, nutritional abnormalities, or congenital or hereditary causes. Abnormalities of bone are usually first identified by lameness or signs of pain.

Most traumatic injuries are fractures that disrupt the normal bone architecture. Fractures can be due to nontraumatic causes, such as those secondary to bone pathology, as in cases of neoplasia or infection (osteomyelitis). Understanding the nature of the fracture is necessary to identify the underlying cause and to help determine the treatment plan.

The most common bone neoplasm is osteosarcoma. However, other primary and secondary bone tumor types can develop. Primary bone cancers are often aggressive and metastasize readily to distant sites. Patients with suspected bone tumors should be thoroughly staged for evidence of metastasis. In cases of osteosarcoma, cellular metastasis often can occur with no gross metastases evident.

Osteomyelitis is an infection of bone, typically of bacterial or fungal origin. Osteomyelitis can occur as a result of penetrating wounds or of hematogenous spread of bacteria, or as a complication after fracture repair.

Nutritional bone disorders are caused primarily by imbalances or deficiencies in minerals, particularly trace minerals such as copper, zinc, and magnesium. Calcium and phosphorus concentrations in food must also be in the correct ratio for normal bone homeostasis. Osteomalacia represents the classic example of imbalanced or deficient calcium and phosphorus intake. Other nutritional disorders can result from excessive protein intake in growing animals. Either inadequate or excessive intake of specific vitamins, particularly vitamins A and D, can influence the growth and development of bone. Aseptic physitis or special osteochondrotic conditions of the physes can result from zinc toxicosis or copper deficiency.

Congenital bone disorders include in utero malformations such as or persistent ulnae or fibulae in foals. Hereditary disorders are often complex and challenging to confirm.