THE MERCK VETERINARY MANUAL
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Developmental Osteopathies in Small Animals

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Angular Deformity of the Forelimb

(Radial and ulnar dysplasia)

Abnormal development of the radius and ulna can occur secondary to distal (radial, ulnar) or proximal (radial) physeal injury or hereditary breed characteristics (Bulldogs, Pugs, Boston Terriers, Basset Hounds, Dachshunds). Asynchronous growth of the two bones leads to shortened limbs, cranial bowing of the bones, elbow joint subluxation, and valgus or varus deformities in the carpus.

Clinical signs include lameness and reduced painful motion in the elbow or carpal joints. Radiography reveals the bone deformations and closed physes.

Treatment is based on correcting angulation and length of the limb and reestablishing joint congruity. Surgical procedures include corrective osteotomy and stabilization with internal or external implants and tension-releasing osteotomies. Prognosis is good for animals without severe limb deformations.

Craniomandibular Osteopathy

Craniomandibular osteopathy is a non-neoplastic, proliferative bone disorder of growing dogs that affects the mandible and tympanic bullae of Terrier breeds. The cause is unknown, but a genetic basis is suspected. The bone lesion is characterized by cyclical resorption of normal bone and replacement by immature bone along endosteal and periosteal surfaces.

Clinical signs vary in severity and include oral discomfort, weight loss, fever, and painful palpable enlargement of the mandible. Radiography reveals bilateral bone proliferation in the mandibles and tympanic bullae.

Therapy is symptomatic and consists of NSAIDs, opioids, or corticosteroids to reduce inflammation and discomfort, along with a soft-food diet. Prognosis is good with mild bone proliferation and animal maturation.

Hypertrophic Osteodystrophy

(Metaphyseal osteopathy)

Hypertrophic osteodystrophy is a developmental disorder of the metaphyses in long bones of young, growing dogs, usually of a large or giant breed. The exact etiology is unknown. The pathophysiology is based on metaphyseal vascular impairment, leading to a failure in ossification and to trabecular necrosis and inflammation.

Clinical signs include bilateral metaphyseal pain and swelling in the distal radius and ulna, fever, anorexia, and depression. Clinical signs may be periodic. Angular limb deformities may develop in severely affected dogs. Radiography reveals metaphyseal bone lucencies and circumferential periosteal bone formation.

Therapy is symptomatic and aimed at relieving pain (eg, NSAIDs, opioids), reducing dietary supplementation, and providing supportive fluid care. Treatment with corticosteroids (prednisone 0.5 mg/lb, PO, bid for 5 days, then tapered as needed) may be superior to treatment with NSAIDs in Weimaraners.

Multiple Cartilaginous Exostoses

(Osteochondromatosis)

Multiple cartilaginous exostoses is a proliferative disease of young dogs and cats characterized by multiple ossified protuberances arising from metaphyseal cortical surfaces of the long bones, vertebrae, and ribs. The exact etiology is unknown, but hereditary (in dogs) and viral (in cats) causes are suspected. Animals may be asymptomatic, and diagnosis is confirmed by palpation and radiography. Surgical excision of the masses is recommended if clinical signs such as lameness or pain develop.

Panosteitis

Panosteitis is a spontaneous, self-limiting disease of young, rapidly growing large and giant dogs that primarily affects the diaphyses and metaphyses of long bone. The exact etiology is unknown, although genetics (in German Shepherds), stress, infection, and metabolic or autoimmune causes have been suspected. The pathophysiology of the disease is characterized by intramedullary fat necrosis, excessive osteoid production, and vascular congestion. Endosteal and periosteal bone reactions occur.

Clinical signs are acute and cyclical and involve single or multiple bone(s) in dogs 6–16 mo old. Animals are lame, febrile, inappetent, and have palpable long bone pain. Radiography reveals increased multifocal intramedullary densities and irregular endosteal surfaces along long bones. Therapy is aimed at relieving pain and discomfort; oral NSAIDs andopioids can be used during periods of illness. Excessive dietary supplementation in young, growing dogs should be avoided.

Retained Ulnar Cartilage Cores

Retained ulnar cartilage cores is a developmental disorder of the distal ulnar physis in young, large, and giant dogs characterized by abnormal endochondral ossification. As a result, progressive physeal calcification ceases, and forelimb bone growth is restrained. The exact etiology is unknown, although dietary causes are suspected.

Clinical signs include lameness and angular limb deformities. Radiography reveals a radiolucent cartilage core in the center of the distal ulnar physis. Treatments include cessation of dietary supplements and osteotomy or ostectomies of the bone to reduce limb deformation. Prognosis is based on severity of the condition.

Scottish Fold Osteodystrophy

This heritable condition of Scottish Fold cats is characterized by skeletal deformations of the vertebrae, metacarpal and metatarsal bones, and phalanges secondary to abnormal endochondral ossification. Affected cats are lame, and affected bones are deformed and swollen. Treatment is by removal of exostoses. Prognosis is guarded.

Last full review/revision May 2013 by Joseph Harari, MS, DVM, DACVS

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