Angular limb deformities are common orthopedic conditions primarily affecting dogs, and a wide variety of these deformities can occur. The class of angular limb deformities covers bone growth disturbances that develop when the growth plate of a growing bone is damaged, making this a problem that affects young, growing animals.
In dogs, the growth plates are responsible for longitudinal bone growth, which takes place largely from four to eight months of age. By one year of age, most growth has completed, with the exception of giant breed dogs. The growth plate is the softest part of the bone, leaving it prone to injury. If an injury to the growth plate occurs during a period of rapid growth, the bone may not grow to a normal length or it may grow twisted or curved. These deformities are most commonly observed in the canine forearm.
The forelimb has two bones between the wrist and the elbow joint: the radius and ulna. The cone-shaped growth plate of the ulna, located near the wrist, is particularly susceptible to becoming injured. When this happens, the ulna ceases to grow because this one growth plate is responsible for about 90% of the bone’s long growth. This forces the radius (the larger bone of the foreleg) to deviate because the two bones are bound together by ligaments. The ulna bone will be shorter than normal and results in a “bow-string” effect in which the radius becomes twisted and bowed.
The cause is most often trauma, such as car accidents or being stepped on. Younger dogs whose bones are still growing – especially large and giant breed puppies – are at much greater risk for developing a severe deformity than older animals after a traumatic injury.
Signs and diagnosis
Angular limb deformities may affect both young large and small breed dogs. They are typically seen when the dog is less than one year of age. Lameness and twisting of the limb are the hallmark signs of an angular limb deformity. The elbow joint may even be pulled out of alignment, causing swelling and pain in this area.
The diagnosis of an angular limb deformity is based on orthopedic exam findings and radiographs of the affected forelimb. X-rays of the affected and normal limbs, with your pet under sedation, will likely be needed in order to develop a precise surgical plan to correct the deformities.
Some breeds, such as Dachshunds, Bulldogs, or Bassets Hounds, have shortened, misshapen legs as part of their normal conformation; these are not considered angular limb deformities in which the opposite limb usually has a normal appearance.
If the ALD occurs in the foreleg and is detected early, before significant angling occurs, surgical removal of a small portion of the ulna is often curative. For more advanced deformities and other locations, various surgical techniques can be used to correct the problem, such as the use of bone plates and screws.
Surgically correcting an angular limb deformity has the advantage of relieving wrist and elbow pain, and preventing arthritis from developing within the joints over time. Uncommon complications following surgery can occur but the vast majority of surgeries are successful.
If the problem isn’t diagnosed quickly and corrected with surgery, there can be much bigger problems in the future for the pet. Abnormal limb deformities result in abnormal and painful joint movement. Osteoarthritis is a common outcome, along with the inability to move normally. If the deformity is severe and left untreated, a dog can actually lose all function in the affected limb.
If you have a young, growing puppy that has been injured, it’s important to seek veterinary care right away.