Exostosis

Exostosis is a medical term that describes abnormal growth of bone tissue. These bony outgrowths occur on the surface of a bone and are usually benign. In dogs, exostosis can occur both in the limb bones and in other areas of the skeleton. Exostoses often develop slowly, but in certain cases they can cause pain or restrictions in movement.

Causes of exostosis in dogs

Exostoses usually arise due to stimulus-induced bone changes or as a reaction to injuries or chronic stress. The most common causes include:

1. Chronic stress or trauma: Repeated mechanical stresses or trauma to the bone can lead to the formation of exostoses. These stresses can be caused by accidents, injuries or unnatural movements.
2. Injuries and fractures: After a fracture, the bone can thicken during the healing process, leading to an exostosis. This happens when the bone tissue formation process is excessively stimulated.
3. Inflammatory processes: Chronic inflammation of the bones or surrounding joints can lead to the formation of exostoses. For example, arthritis (joint inflammation) can stimulate bone growth.
4. Genetic factors: In some dogs, genetic predispositions can play a role, particularly in dog breeds that are susceptible to bone diseases.
5. Bone tumours: In rare cases, an exostosis can be caused by a benign bone tumour such as an osteoma. These tumours lead to abnormal bone growth.

Symptoms of exostosis in dogs

The symptoms of an exostosis depend on the localisation and size of the bony outgrowth. Common signs are:

• Swelling: A palpable hardening or swelling on the affected bone can be the first sign of an exostosis.
• Pain: If the exostosis presses on nerves, muscles or other tissues, it can cause pain. The dog may be sensitive to touch or withdraw when the affected area is touched.
• Movement restrictions: Exostoses on the limb bones or near joints can restrict mobility, which can lead to lameness or stiffness.
• Limping or lameness: With exostoses on the legs, the dog may show obvious limping when walking, especially after physical activity.
• Deformities: In severe cases, exostoses can lead to visible deformities of the affected limbs or joints.

Diagnosis of exostosis in dogs

The diagnosis of an exostosis is made by a combination of clinical examination and imaging techniques:

1. Clinical examination: The vet palpates the affected area to detect swelling or hardening. The dog is also examined for pain or movement restrictions.
2. X-ray: An X-ray image clearly shows the abnormal bone growth and allows the size and location of the exostosis to be determined.
3. CT scan or MRI: In more complicated cases or if there is suspicion of a connection to soft tissues, a CT scan or an MRI may be required to obtain a more precise representation of the bone and surrounding structures.
4. Biopsy: If there is suspicion that the exostosis is caused by a bone tumour, a biopsy can be performed to take and examine a sample of the bone tissue.

Treatment of exostosis in dogs

Treatment depends on the severity and symptoms of the exostosis. For small, asymptomatic exostoses, immediate treatment may not be necessary, whereas surgical removal may be considered for painful or restrictive growths.

Conservative treatment:

• If the exostosis causes only minor or no symptoms, conservative therapy with painkillers and anti-inflammatory medication may be sufficient to provide relief for the dog.
• Restricting movement can help prevent further damage, particularly with exostoses on the legs.

Surgical removal:

• If the exostosis causes pain or restricted movement, surgical removal may be required. The surgeon removes the excess bone to restore mobility and reduce pressure on surrounding tissue.
• The operation is generally performed under general anaesthesia, and careful postoperative care is required to support healing.

Physiotherapy:

• After surgical removal or during conservative treatment, physiotherapy can be helpful to restore mobility and prevent muscle atrophy.

Prognosis

The prognosis for dogs with exostoses is generally good, particularly if the exostosis is diagnosed and treated early. For smaller exostoses that cause no symptoms, long-term treatment is often unnecessary. After successful surgical removal, most dogs recover well and can lead a normal life.

However, if the exostosis is associated with an underlying condition such as a bone tumour, the prognosis depends on the type of tumour and the stage of the disease.