How does a veterinarian diagnose carpal hyperextension?
In many cases, a tentative diagnosis of carpal hyperextension can be made based on initial observation. However, your veterinarian will perform a thorough physical exam and evaluate your dog’s overall health and examine all of your dog’s bones and joints. Dogs with carpal hyperextension may also have abnormalities in other joints, so a thorough physical examination is important.
Your veterinarian will likely recommend radiographs (X-rays) of the affected leg(s). Sedation or anesthesia is often required for these radiographs, in order to get good s that provide as much information as possible. Although ligaments cannot be viewed on radiographs, taking “stressed views” (in which the carpus is manipulated into various positions) can aid in the diagnosis of ligament damage, by assessing the stability of the joint. Radiographs can be used to look for fractures of the small bones within the carpus.
Further imaging is often required to confirm the diagnosis and better characterize the specific ligament damage that is causing carpal hyperextension. Your veterinarian may refer you to a veterinary specialist for computed tomography (CT) or magnetic resonance imaging (MRI).
Treatment of carpal hyperextension depends upon the severity of the condition.
In some cases, including developmental carpal hyperextension and mild trauma, non-surgical treatment may be an option. Medical therapy typically involves a combination of splints and physical therapy, with the goal of restoring normal function to the stretched or sprained carpal ligaments.
In many cases of carpal extension, however, surgical repair is required. It is challenging if not impossible to repair damaged carpal ligaments, so this condition is typically treated with surgical fusion of the carpal joint, also referred to as carpal arthrodesis. In this surgery, your veterinarian will use a combination of plates and screws to immobilize the carpus in a functional position. In many cases, this means fusion of the entire carpus (known as a pancarpal arthrodesis), although partial carpal arthrodesis may be recommended in some scenarios. Although this surgery will prevent normal mobility at the carpal joint, it will provide stability and allow your dog to bear weight normally on the limb.
What are the signs of carpal hyperextension?
Dogs with carpal hyperextension have a noticeable bend at the wrist, forcing their lower limb into an abnormally flattened position. In some cases, the dog may still run and play normally (albeit with an abnormal gait), while in more severe cases the dog may appear reluctant to move.
If carpal hyperextension is caused by trauma, it may be associated with pain and swelling. However, not all dogs with carpal hyperextension will act painful.
In some cases, pressure sores or ulcers may develop where the carpus contacts the ground. These lesions may cause an increase in pain, while also causing your dog to lick or chew at the affected area.
How can I tell if my dog has carpal hyperextension?
There are three common forms of injury to the carpus causing hyperextension:
1. The first form affects puppies and involves an abnormality in the development of the ligaments supporting the carpal joint. Affected puppies walk with excessive extension of the carpus (with a gait more like a bear than a dog). Both wrists tend to be affected in puppies with this condition and in some extreme cases, the hock joints (ankles) in the hind limbs can also be affected. Puppies that have ligament laxity and subsequent hyperextension of the carpus as a result of prolonged immobilisation in a bandage are only affected on the bandaged leg.
2. The second form of injury to the carpus is the result of trauma. There are varying degrees of sprain injury affecting the carpus. The amount of lameness and swelling depends on the severity of trauma. Some dogs will have an obvious postural abnormality with inappropriate deviation of the affected joint.
3. The third form of carpal injury is degenerative hyperextension of the wrists. This problem affects older dogs and is especially common in Collie breeds. There is a tendency for one or both carpi to gradually sink until they completely collapse.
Some problems affecting the wrist joint also affect other joints and are in the group of polyarthritides. These are the animal equivalent of rheumatoid arthritis and can affect the joints of the fore and hind limbs of dogs and cats.
Carpal hyperextension is typically diagnosed following a multimodal evaluation process. Firstly your dog will be examined by one of our orthopaedic clinicians to ascertain the nature of the disease. Following this, your dog will most likely be admitted to the hospital to allow radiographs of the affected joints under sedation or general anaesthesia. With this particular disease, we perform a series of specific radiographs called ‘stressed views’. This entails taking a radiograph of your dog’s carpus in the position that truly reflects the extent of the hyperextension i.e. mimicking a fully weight-bearing position. This helps the orthopaedic clinician assess which ligamentous structures are damaged and facilitate the overall decision-making process as to what treatment is best for your dog.
Your dog may also require additional diagnostic imaging such as CT or MRI which will be performed by our advanced diagnostic imaging team. Your dog will receive one-to-one nursing care throughout their imaging process by one of our nurses from the prep nursing team who are all highly trained and experienced in anaesthesia and sedation. Following clinical examination and diagnostic imaging, the orthopaedic clinician will be able to advise on the most appropriate course of treatment for your dog, be it conservative (non-surgical) management or surgical management.
Physical examination can give us a good idea of the nature of the problem. We may perform special stressed radiographic tests to help us assess which ligamentous structures are damaged. In animals where broken bones are suspected but are not seen on the plain radiographs, we frequently recommend a CT scan. Occasionally, MRI can provide useful additional information.