Hip dysplasia (HD)

What is Hip dysplasia?

This is a condition where there is abnormal development of the hip joint. There is a genetic component to the condition but a puppy is born with normal hips and the abnormalities develop as the dog gets older. The condition leads to joint laxity (slackening of the soft tissues around the joint). The laxity can develop as early as 7 weeks of age. As the hip joint is a ball and socket joint, the two sides of the joint do not fit together properly (incongruent) and this leads to abnormal shaping of the joint. The ball flattens and the socket widens to become saucer-like. Secondary osteoarthritis develops as a result of this condition. The condition frequently affects both hips at the same time.

What causes hip dysplasia?

This condition has genetic (multiple genes are involved) and environmental components. The genetics are determined by the parents whereas environmental factors relate to anything other than the patient’s DNA, such as body condition, diet, etc. A patient will only develop hip dysplasia if it has the genetic programming. Environmental factors alone will not cause this condition.

What are the signs of hip dysplasia?

The most common sign is limping in the back legs. One or both legs may be affected. The signs can be very varied with some patients appear worse after rest and struggle to rise, whereas others may be lame during a walk. Some patients have a reduced tolerance to exercise and others have a swaying hind limb gait (wiggly bottom). This condition is seen predominantly in dogs but can also be diagnosed in cats. Many patients will present at 6-12 months of age. Older dogs can also present if the osteoarthritis is becoming debilitating. This condition may be present in some dogs and they show no obvious clinical signs. Hip dysplasia can be uncomfortable with young dogs showing pain due to stretching of the joint soft tissues which contain nerve fibres. Older dogs can show discomfort due to loss of cartilage in the joint.

Diagnosis

We may become suspicious of this condition when certain clinical signs are seen such as lameness, stiffness after rest, an inability to jump etc. The definitive diagnosis is made when a combination of clinical examination, assessment under sedation / anaesthesia and radiography (x-ray) is performed.

Radiography can document the presence of hip dysplasia but correct positioning is required. Assessing a patient which is under sedation or anaesthesia also allows the surgeon to detect any laxity in the joint during hip manipulation.

Hip dysplasia treatment

Treatment is based on a patient’s clinical signs and severity of condition. Not all treatment options are appropriate for all animals and so it is our surgeons’ job to discuss with you the most appropriate treatment option for your pet.

Non-surgical / conservative management

If the clinical signs are mild or if the condition has been diagnosed incidentally, then this may be the most suitable option. The mainstay of this treatment is body weight control, exercise control and standardisation, physical therapy, anti-inflammatory pain killers and dietary supplements. With this management, we would hope for a long term improvement so if the positive results are only transient, other options may need to be discussed.

Surgical management

There are two types of surgical treatments. Procedures that alter the anatomy of the hip and others that save the limb but remove the hip joint, so called salvage procedures.

Anatomy altering surgery

• Juvenile pubic symphysiodesis (JPS)

Premature fusion of a portion of the growing part of the pelvis is performed to improve the coverage of the ‘ball’ (femoral head) by ‘socket’ (acetabulum). If successful this alters the hip anatomy to try and stop the hip joint trying to luxate (dislocate). The surgery has the best chance of working in dogs under 5 months of age. The surgery is relatively straightforward and involves electrical cauterisation of pubic symphysis (part of the underside of the pelvis). Only patients with mild laxity detected by manipulation and radiographic tests should be treated since dogs with more severe signs are unlikely to respond to this procedure.

• Double or Triple pelvic osteotomy (DPO/TPO)

These procedures again try to improve coverage of the ‘ball’ (femoral head) by ‘socket’ (acetabulum) by making two or three cuts in the bones of the pelvis. The fragments are fixed in the new location using a bone plate and screws to alter the pelvic shape. These procedures are again most effective in patients with mild laxity confirmed using manipulative and radiographic tests. Assessment for DPO/TPO requires a specific series of manipulative tests and radiographs to be performed by experienced orthopaedic surgeons. Older patients or those with osteoarthritis will not respond favourably to this procedure.

Surgical salvage procedures

• Total hip replacement (THR)

This is a technique where the hip joint is removed and replaced with a metal ball and plastic cup. This is a technically very demanding procedure and should only be performed by experienced and ideally specialist orthopaedic surgeons. Due to recent developments in the implant technology this procedure can be performed on patients as large as Great Danes and as small as Chihuahuas. This procedure can also now be performed in cats. Although the disease may be present in both hip joints, some patients will only require the procedure performing in one joint to significantly improve their quality of life. Others will need both hips replacing but this will be discussed at the time of consultation. The success rate for THR is approximately 90%, and most patients are more comfortable within a few days of surgery. We expect most patients to return to full activity assuming there are no complications.

• Femoral head and neck excision (FHNE)

This procedure involves removal of the hip joint and a false hip joint is allowed to develop from scar tissue. This procedure can be used where THR is not a viable option, for example due to financial constraints or variations in individual anatomy that preclude THR. Most patients undergoing this procedure will be left with a limp or gait abnormality but pain relief is usually satisfactory to improve the quality of life. Physical therapy (hydrotherapy and physiotherapy) can help maximise limb function for these patients.