Hip Dysplasia in Dogs

Despite many years of selective breeding, hip dysplasia remains one of the commonest orthopaedic diseases of dogs. It is often confused with osteoarthritis of the hips in older dogs which is incorrect; hip dysplasia is a developmental disease that can start within the first few weeks of life, whereas osteoarthritis is the consequence. Dogs with hip dysplasia usually fall into two categories when first being presented to the veterinarian for this condition:

1. When they are less than 12 months old, and pain arises due to the joint laxity, the key initiating factor in hip dysplasia. 2. When they are over 2 years old, and pain is due to osteoarthritis caused by the hip dysplasia.

Between these two stages, symptoms often decrease. This is because the joint laxity causes thickening of the joint capsule and surrounding tissues, thereby restricting movement. Increased muscular support also helps to mask the symptoms by providing external support.

It is well documented that developmental skeletal problems tend to occur in larger breeds of dogs, with force through the joint directly proportional to bodyweight. However, genes are not the only cause. Factors such as diet, bodyweight and exercise play a crucial role. It has been suggested that as few as 24% of young dogs with severe signs of hip dysplasia on xrays will actually develop symptoms of the disease if managed appropriately with regard to the factors mentioned above.

So, what are the signs to look out for? Symptoms may range from mild stiffness on getting up, or a reluctance to jump, to the classic wiggle seen as the dog rotates its pelvis as it is walking, to reduce the extension of the hip which is painful.

On examination by a veterinarian, younger animals may show increased joint laxity, essentially looseness of the ball (femoral head) in the socket (acetabulum). Older animals typically show reduced flexibility of the hip joints, with a grating sound produced on manipulation of the joint (crepitus) and muscle wastage of the hindlimbs.

One must also bear in mind that there are other diseases that can affect dogs of this age, such as diseases of the nervous system (e.g. lumbosacral stenosis, degenerative myelopathy). Though rarer than hip dysplasia, they must be considered before making a diagnosis.

How is diagnosis confirmed by the veterinarian? 1. Clinical examination. Though joint laxity in the hips can often be felt with the dog conscious, it can be painful and therefore is best performed with the dog under general anesthetic or heavy sedation. This will also reduce the effects of muscle tension. There are 3 tests that vets can perform on the anesthetized dog to diagnose hip dysplasia: the Barlow test, the Bardens test and the Ortolani test. These tests invariably involve applying pressure and manipulating the hip in a certain direction to cause partial of full dislocation of the femoral head.

2. Xrays. Good quality, well positioned radiographs are required to assess hips for dysplasia and general anesthesia is a necessity to achieve this. If a dog is to be used for breeding, it is often hip scored prior to doing so. This is often done in the absence of any symptoms at all, in perfectly healthy dogs. The radiographs are then sent off to the national Hip Dysplasia Scheme assessors for examination, where the hip joints are scrutinized to predict the likelihood of the disease occurring.

My dog has been diagnosed with hip dysplasia. What are the management options? This is relatively straight forward. Dogs can either be treated conservatively (without surgery) or surgically. Conservative management is NOT doing nothing, it should be a PROACTIVE option. A programme should be designed for the individual dog to address weight control, exercise management, physiotherapy and pain control.

CONSERVATIVE MANAGEMENT 1. Weight Control Excessive weight should be prevented in puppies, and adults should be maintained at or below normal adult bodyweight. Simple weight reduction has been shown to result in a significant improvement in lameness in adult dogs with osteoarthritis secondary to hip dysplasia.

2. Exercise Management A suitable level of exercise should be determined for each individual dog to maintain muscle development and fitness without exacerbating the clinical signs. Obviously this must be integrated with the owners lifestyle expectations. Regular, low impact exercise is preferable to intermittent, vigorous exercise. Several short walks a day is better than a huge walk every other day!

3. Physiotherapy The benefits of physiotherapy in the treatment of musculoskeletal diseases of animals have only recently been recognized. Hydrotherapy is an excellent form of exercise for obese, unfit and disabled animals. This is because the buoyancy the water provides helps overcome the effects of gravity, and muscles are worked out without placing too much force through the joints.

4. Pain Control Non steroidal anti inflammatory drugs (NSAIDS) are a key component of conservative management. They work by blocking the formation of inflammatory mediators which cause pain, specifically by blocking the cyclooxygenase enzymes COX 1 and COX 2. The modern NSAID drugs preferentially inhibit COX 2 enzymes, which reduces the side effects associated with them, such as stomach ulceration and kidney damage. The most commonly used NSAIDs are carprofen and meloxicam.

5. Nutraceuticals and cartilage protecting drugs These are slow acting, disease modifying drugs that may help to control osteoarthritis. Orally administered forms of glucosamine sulphate and chondroitin sulphate have been shown to improve joint function in humans. Whilst the exact mechanisms of osteoarthritis may differ between dogs and humans, anecdotal evidence suggests they are beneficial and they have become popular with many veterinarians. Above all, they cannot do harm so are often prescribed, despite the absence of hard scientific evidence in their favor.

SURGICAL MANAGEMENT Surgical treatment can be divided into preventative or salvage. Preventative treatments include the following:

1. Triple Pelvic Osteotomy (TPO) This is indicated in young animals with painful hips that have failed to improve with conservative treatment. The operation provides stabilization of the hip, which reduces the progression of osteoarthritis. It can be performed on any age of dog, but dogs have to show minimal remodeling of the hip joint on xrays and so most that meet the criteria are less than 8 months old.

2. Perineal myectomy This involves removing part or all of the pectineus muscle, the spasm of which is thought to cause pain in the growing dog with hip dysplasia. However, whilst this procedure does tend to produce some pain relief, it is now considered outdated by many.

3. Intertrochanteric osteotomy Although effective in decreasing pain and reducing secondary osteoarthritis, it is less effective than TPO and there is a risk of fracturing the femur during the operation, meaning it is no longer recommended.

4. Pubic symphysiodesis A new technique for young dogs considered to be at risk of developing hip dysplasia. The procedure is most effective in very young animals, which are usually not showing any symptoms at all, making it a controversial treatment option and not recommended at present.

Salvage options include: 1. Femoral Head & Neck Excision This involves surgically removing the head and neck of the femur. Heavier dogs have a much poorer outcome than lighter dogs. It tends to give positive results in dogs less than 17kg in bodyweight. Obese dogs fare poorly. Younger, more active dogs can respond very well to this procedure.

2. Total Hip Replacement This is not the solution for every dog with a painful hip. Owners must be aware that while the outcome is usually very good, complications can rarely occur and when they do they are disastrous.

The ideal candidate for a hip replacement is a well trained, sensible, medium to large breed dog, which was previously active, and has a painful hip that is unresponsive to medication. The owners should be sensible and compliant, with funds to spend not only on the surgery (which is expensive), but also on dealing with potential complications that may occur, which can be equally costly. If these criteria are not all met, it may be more appropriate to perform a femoral head and neck excision.