Forelimb Angular Limb Deformities in Dogs

What is an angular limb deformity?

An angular limb deformity (ALD) is an abnormal alignment in one or more bones of the leg. ALDs are most commonly seen in the forelimb (front leg) of dogs, are rare in the hindlimb (back leg), and are uncommon in cats. They cause the leg to curve, twist, or become shortened.

What causes an angular limb deformity?

In dogs, an ALD is usually caused by the radius and ulna (the two bones of the lower forelimb) growing out of sync (asynchronously). These bones are attached to each other by ligaments and connect the elbow joint to the wrist joint. Typically, they grow at similar rates, resulting in a straight forelimb. But if one bone stops growing while the other continues to grow, it causes deformities in one or both bones. Deformities may include twisting, bowing, or abnormal shortening compared to the other leg.

There is evidence of some genetic predisposition for ALDs. Dogs that have been bred to be shorter (chondrodystrophic breeds) like the dachshund, bulldog, and pug are more commonly affected. ALDs are most commonly caused by damage to one of the bones’ growth centers, called growth plates or physes. The growth plate near the bottom of the ulna (the distal ulnar growth plate) is at highest risk of damage because of its pronounced “V” shape. When a growth plate is damaged, the bone stops growing or, if it is partially damaged, the bone may grow abnormally. In both cases, it leads to an ALD.

What are the consequences of angular limb deformities?

ALDs cause abnormal stress on joints and ligaments. This stress can lead to abnormal movement, misaligned joints (elbow incongruity), osteoarthritis, pain, and progressive lameness.

How is an ALD diagnosed?

Diagnosing an ALD is not always straightforward. Dogs with pronounced ALD may have the following signs:

• An obviously crooked leg
• Toes that point outwards or inwards
• A shorter limb on one side compared to the other

More subtle signs of an ALD can include:

• Abnormal nail wear or scuffing
• Abnormal way of walking (gait)
• Lameness (limping)
• Soreness when the elbow or wrist (carpus) is pressed (palpated)

Your veterinarian will perform an orthopedic examination, assessing your dog’s bones and how their joints move. Radiographs (X-rays) are often recommended to better assess the bones and joints. Your veterinarian may recommend a CT to provide three-dimensional information on the bones and ligaments in the leg. This information is often used for surgical planning.

How is an ALD treated?

Treatment for an ALD depends on the severity of the deformity. For example, breed-associated, symmetrical, non-painful angular limb deformities may be treated conservatively to minimize osteoarthritis and pain. Conservative treatment can include maintaining a healthy weight, low-impact exercise, physical rehabilitation, and pain medication as needed.

Surgery may be recommended in dogs that develop an ALD because of trauma. In puppies, the goal of surgery is to restore normal bone growth, reduce differences in mature leg length, and correct the bend in the leg as much as possible. Early surgery may also help reduce future joint damage. One surgery used to correct ALD in puppies is the proximal dynamic ulnar osteotomy, in which the ulna is cut to allow the radius to grow with minimal restriction, reducing ALD.

The surgeon will determine the type of surgery needed, usually after more extensive assessment of the deformity, such as with a CT scan. Your dog’s age is an important factor in determining the appropriate surgery as the surgeon will need to consider current and future bone growth.

What post-operative care is needed?

Post-operative care will depend on the type of surgery. It’s important to follow all your surgeon’s instructions closely to reduce complications. 

• Your dog may need to wear a bandage or splint to protect the limb for several weeks. 
• Jumping must be prevented and your dog must be on a leash when outside for bathroom breaks. 
• Your dog may need to wear an Elizabethan collar to keep them from licking their incision. 

Your surgeon will provide details on how much you need to restrict your pet’s activity and when to bring your dog back for reassessment, bandage changes and X-rays. Physical therapy is often recommended to help restore strength, manage pain, and improve movement.

What complications can occur after surgery? 

Complications include:

• Reduced or non-healing of the surgical bone correction
• Infection
• Bending, breaking, or loosening of metal implants 
• Recurrence of the deformity in growing puppies that may require additional surgery

What is the prognosis?

Bone growth can be variable, so achieving perfect alignment in growing puppies is not guaranteed. In rare cases, repeated surgical correction may be recommended. 

The long-term prognosis depends on how straight the leg becomes once bone growth is complete and whether any osteoarthritis has occurred secondary to the deformity. Generally, the outcome with surgery is considered good, with dogs experiencing improved comfort and limb function with a reduction in osteoarthritis development.