- What is Hypertrophic Osteodystrophy?
- Who gets Hypertrophic Osteodystrophy?
- What are the Signs of Hypertrophic Osteodystrophy?
- How is Hypertrophic Osteodystrophy Diagnosed?
- Why did my Dog get Hypertrophic Osteodystrophy?
- How is Hypertrophic Osteodystrophy Treated?
- Can Hypertrophic Osteodystrophy be Prevented?
- What is the Prognosis for my Dog with Hypertrophic Osteodystrophy?
Hypertrophic Osteodystrophy (HOD) is known by many names, including skeletal scurvy, metaphyseal osteodystrophy, metaphyseal dysplasia, Moeller-Barlow disease, among others. It is a developmental disease that affects the metaphyses of long bones, which is the region of growth at the end of the bone, adjacent to the growth plate. A series of events occurs, beginning with a disruption of the blood vessels near the growth plate. These vessels become distended and bleed into the bone. Instead of hardening and ossifying like normal, growing bones should, the bone in this region dies. It then gets reabsorbed, and develops microfracturing as a result of weakening of the bone structure. In response, the body lays down new bone on the surface of the bone. This results in the ends of the long bones becoming significantly thickened and swollen. The radius, ulna, and tibia bones are most commonly affected, but it can also occur in the ribs, jaw, and bones of the paw. (show dog/joints with HOD)
HOD occurs in young, rapidly growing dogs, usually between the ages of 3 to 6 months. It primarily occurs in large and giant breeds including Great Danes, Boxers, German Shepherds, Irish setters, Labrador retrievers, and Weimaraners. Males are more commonly affected than females, and the highest incidence occurs in the fall season.
Clinical signs usually begin with an acute onset of lameness. Puppies can be so severely affected that they refuse to stand or walk, especially if multiple limbs are affected. Other clinical signs include fever, anorexia (not eating), depression, diarrhea, discharge from the eyes, tonsillitis, thickening of the footpads, pneumonia, lethargy, and pain and swelling in the affected bones. Signs of HOD can wax and wane, and patients can go through periods of relapse.
Diagnosis is based on the patient’s history and physical exam findings. Findings on physical examination range from mild lameness to severe lameness affecting all four limbs. More severely affected animals are often unable to stand or walk. Long bone metaphyses are swollen, warm, and painful on palpation. Swelling is often present in all four limbs; however, forelimb swelling may be more obvious, especially in the radius. Severely affected dogs may be depressed, anorexic, and have a fever of up to 106° F. Your veterinarian will likely take radiographs of the limbs to aid in diagnosis. Dogs with HOD will show a line of lucency on an x-ray where destruction of the bone has taken place, adjacent to the growth plates. Sometimes new bone growth is also visible on radiographs, and the area of bone near the growth plate will be bowed. (show example rads)
The exact cause of HOD is unknown. Theories include virus or bacterial infections, but no specific pathogens have been isolated. Some believe that it is due to Vitamin C deficiency, because dogs with HOD show similar signs and bony changes as those that have scurvy. However, dogs can synthesize their own Vitamin C, and supplementation of the vitamin to affected dogs does not always alter or cure the disease. Others attribute the disease to a diet that has an excess of protein, calories, and/or calcium, but studies have not been conducted to prove this.
Dogs with hypertrophic osteodystrophy are mainly treated with supportive care. This includes prescribed anti-inflammatories to decrease pain and swelling, antibiotics, fluid therapy, nutritional support, vitamin C supplementation, and in some cases, corticosteroids. Exercise should be limited to short leash walk on grass or other soft surfaces. In some cases, physical therapy is indicated in order to maintain muscle tone. Corrective surgery is sometimes required in dogs whose bones have become twisted due to the damage to the growth plates.
Because so little is known about the cause of the disease, as far as we know there are no effective preventative measures. As a matter of good health and prevention of other conditions, however, giant and large breed puppies should be fed a diet that promotes slow, steady growth, rather than rapid growth.
Prognosis for hypertrophic osteodystrophy can range from fair to poor. HOD occurs episodically, and can last for a few weeks at a time. Recurrence is expected in most dogs, until they reach 8-10 months of age. Because the disease causes a disruption in normal bone development, it can result in deformity of long bones, or in the most severe cases, dwarfism. In cases where severe debilitation or multiple, severe relapses occur, euthanasia may be the most humane option.