What is Hypertrophic Osteopathy?

Hypertrophic osteopathy (HO) is a condition that results in new bone formation on the bones of the limbs. The new bone formation, termed periosteal proliferation, begins with the bones of the paw, and gradually ascends up the limb. The mechanism of the new bone formation is unknown, but it starts as a result of a disruption of the nerve signals, causing a change in blood supply to the covering of the bones (periosteum), which results in new bone forming on the surfaces. This new bone appears nodular. They can affect all four limbs.

Who gets Hypertrophic Osteopathy?

Any breed or size of dog can get HO, but because it is usually secondary to another disease process, namely neoplasia (cancer), it is most often seen in older animals.

What are the Signs of Hypertrophic Osteopathy?

Clinical signs usually begin with lethargy, reluctance to move, and swelling of the lower limbs. These signs may appear acutely or gradually. Affected dogs with show signs of lameness, as well as pain on palpation of the extremities.

How is Hypertrophic Osteopathy Diagnosed?

Upon physical exam in dogs with HO, affected limbs are found to be warm and swollen. Radiographs can be used to aid in diagnosis, and will reveal a uniform formation of new bone on the surfaces of the bones, but do not affect the joint. Because this condition is secondary to diseases elsewhere in the body, an effort should be made to determine the underlying cause. A thorough physical examination is essential when evaluating affected animals. Radiographs are also used to identify if there are any thoracic or abdominal masses or other possible causes of the hypertrophic osteopathy. (show rads)

Why did my Dog get Hypertrophic Osteopathy?

HO is a slightly complicated disease in that it typically results from an underlying condition. Primary conditions resulting in HO are numerous, and include: disease in the chest such as a rib tumor, lung tumor, lung abscess, parasite infection associated sarcoma of the esophagus, patent ductus arteriosus, congenital megaesophagus, infective endocarditis (infection of the heart valve), mycobacterial pneumonia, bronchial foreign body with lobar pneumonia; disease in the abdomen such as kidney tumors, prostatic tumors and other masses within the abdomen. The most common underlying cause of hypertrophic osteopathy in dogs is metastatic pulmonary lesions. Hypertrophic osteopathy seems unusually prevalent in animals that have undergone primary amputation for osteosarcoma that has subsequently metastasized to the lungs.

How is Hypertrophic Osteopathy Treated?

Treatment should be targeted at the underlying, primary disease process. Once the primary lesion is removed, the HO usually resolves.

Can Hypertrophic Osteopathy be Prevented?

The possible causes of hypertrophic osteopathy are numerous. Therefore, efforts to prevent HO would be unrealistic. The key is to identify the primary disease process as early as possible and treat it.

What is the Prognosis for my Dog with Hypertrophic Osteopathy?

If the primary tumor can be removed and has not spread, the prognosis is excellent. The lameness and bone proliferation caused by HO will likely resolve. However, if the tumor is not treatable or is inoperable, the prognosis is very poor.