Humeral condylar fissure (HIF)

Humeral condylar fissure (HIF), also known as Incomplete ossification of the humeral condyle (IOHC), is an inherited disease that is particularly common in spaniels. It causes lameness in young dogs and often requires surgical treatment.

In the fetus the long bones in the skeleton are made from cartilage. As the fetus develops, calcium is deposited in these cartilage structures making them bony and stronger. Bone is formed in the ends of the long bone structures and in the main shaft of the bone and these bony areas expand until they join and fuse to form one solid bony structure. Most of the process occurs before a puppy is born but it also continues in the young puppy after birth and is usually complete in the elbow around 4 months of age.

The elbow is the joint between the bone called the humerus (in the upper limb) and the radius and ulna bones (in the lower limb). The humerus is a long straight bone but on the end that forms the elbow joint it has 2 bulbous areas (the condyles). Each of these condyles has a separate center from which their bony structure forms. This bony center grows until it meets the bone growing from the center of the other condyle and the 2 sides become fused together (and fuse with the main shaft of the bone) to form one solid bone. In some young dogs these separate bony centers do not fuse properly, leaving a fibrous cartilage band between the bulbs on the end of the humerus. Because the cartilage is not as strong as bone this remains an area of inherent weakness. No-one really knows exactly why the development goes wrong in some dogs, but HIF is often associated with other developmental conditions of bones such as elbow dysplasia. The condition commonly, but not always, affects both left and right legs, but signs may develop on one side before the other.

The weak line between the 2 condyles in the elbow makes it more likely the joint between them may fracture – and this can occur during normal activity in affected dogs.

Dogs with HIF can present in one of three ways:

1. Forelimb lameness – often are lame on and off for many months and this may vary in severity (from very subtle to quite severe) and appear to respond to rest or painkillers but keeps returning.

2. Other dogs don’t have any problem until they develop a fracture in the elbow, which often occurs during normal activity (so no particular traumatic event is reported). The sudden lameness is very severe – usually the dog can’t put their leg to the ground.

3. Sometimes the disease is picked on when X-rays are taken for some other reason and the dog has shown no sign of pain or lameness. In some cases, X-rays do not show the problem and it is picked up on more advanced imaging (CT scans).

It is thought the disease has a genetic component and is passed down from parents to their puppies. However, it is possible for both parents to be clear of clinical disease but still produce puppies that are affected. It is far more common in certain breeds, especially Springer spaniels and Cocker spaniels, but also Labrador retrievers and Rottweilers. Some people think that being overweight may make spaniels more likely to develop a humeral fracture if they have HIF, and this would make sense as carrying excessive weight will put more strain on the weak part of the bone.

Your veterinarian will probably be suspicious that your dog might have HIF if they are a breed in which the condition is common and have a chronic lameness or develop an elbow fracture without any obvious trauma. They will first want to conduct a detailed examination of the bones and joints of the affected leg and may detect elbow pain especially if pressure is applied to the outside of the elbow or when the elbow is fully extended.  If a fracture has occurred, there will be swelling of the leg and a lot of pain on manipulation of the elbow.

Whatever the cause, if your young dog has a long-term lameness or a sudden severe lameness, your veterinarian will want to investigate further with some imaging studies. A radiograph or CT of the joints will help to identify the underlying cause. If there has not been a compete fracture through the cartilage plane it can be difficult to make a confirmed diagnosis of HIF on conventional X-rays. There might be some abnormal new bone formation around the elbow joint, which would be highly suspicious in a young dog. It is much easier to make the diagnosis if a CT scan of the elbow is made. If a fracture has occurred this is generally more straightforward to see on X-rays. If HIF is recognized in one elbow your veterinarian will probably recommend that the other elbow is imaged to see if the same disease is present there – even if there are no signs of lameness on that leg.

Simple management of mild lameness includes restricting exercise to low impact activities (lead walking, swimming) and treatment with non-steroidal anti-inflammatory drugs. If a fracture has occurred cage confinement before surgery is essential to prevent further damage to the joint before the operation.

The treatment for HIF is to stabilize the 2 condyles together across the cartilage line. This is generally done by placing a large screw through the bone from one condyle to the other. Although this may appear to be a straightforward procedure there are a lot of potential complications if it is not done correctly so it is important to make sure that the veterinarian undertaking the procedure is experienced in this area.

After surgery pain relief is important with anti-inflammatory drugs for a minimum of 2-3 weeks postoperatively. Exercise must be restricted immediately after surgery. This starts with confinement in a cage or to a single small room with non-slip flooring with lead exercise for toileting purposes only. Exercise can then gradually be increased over 6 weeks, according to the schedule designed by your veterinarian.

X-rays are repeated 6-8 weeks later to monitor the progress of healing and at this stage your veterinarian will help you plan the next stages of rehabilitation for your pet. Further X-rays or CT may be required in certain cases if healing is slow or incomplete.

The outcome is generally good if appropriate surgery is undertaken quickly. Around 9 out of 10 dogs will be sound within a few weeks of the surgery and return to a normal life.  However, even after surgery the fibrous defect in the humerus may not heal and if this happens the dog will always be more at risk of the screw in the elbow breaking. As with any surgery there are small risks associated with the anesthetic or the risk of post-operative infections.

Osteoarthritis is common in dogs with HIF (often developing even before surgery). This osteoarthritis will progress with time despite treatment and may result in stiffness and lameness in older animals which necessitates long-term anti-inflammatory treatments for pain relief.

Since HIF is an inherited disease, it is important not to breed from affected dogs. However, because unaffected parents can still pass on the disease, care should be given when considering breeding from apparently normal dogs that have produced puppies with HIF in the past.

HIF requires rapid treatment to get the best outcome for your pet. If you are worried about any signs in your dog, always contact your veterinarian for further advice.