HIPS 101 – WHAT IS HIP DYSPLASIA

Having a beloved dog diagnosed with a painful joint condition like hip or elbow dysplasia can be devastating for owners, but treatment options are available, either to rectify problems or manage pain and discomfort

When Michael Moore realised that his five-month-old Rottweiler puppy was showing signs of stiffness and pain in the morning, he was very concerned. After a visit to the vet and a diagnosis of bilateral hip dysplasia, Michael was devastated! He had carefully selected the breeder – a very reputable one – and checked the hip gradings of the puppy’s parents and grandparents.

What Michael didn’t know is that while hip dysplasia is genetic, other components play a significant role in the development and progression of the disease.

Genetics and environmental factors
Dr Marthinus Hartman, a senior lecturer in small animal surgery at the Faculty of Veterinary Science at Onderstepoort, says that depending on the research literature consulted, one can say that the genetic component of hip dysplasia (HD) is between 25% and 50%. “There are various genes associated with hip dysplasia that have been identified and we can test for them today,” explains Dr Hartman. “By identifying these dogs through radiographs and not breeding with them, we can eliminate up to half the problem, but there is another 50% to 75% that involves management of the puppy in the first eight months of life.” (See the box ‘Environmental factors’.) Hip dysplasia is common in many dog breeds – some medium dog breeds, but most large and giant breeds.

The difference between normal hips and dysplastic hips

NORMAL HIPS

The ball is round and fits well into a deep socket. The red line highlights the socket and the green line outlines the femoral head (ball) and neck. Notice the hourglass appearance of the thin femoral neck. The region of solid green colour represents the part of the femoral head that is buried within the socket.

ABNORMAL HIPS

This dog has severe hip dysplasia. The femoral head and neck are outlined in green. Notice how thickened this femoral neck is compared to the normal dog hip x-rays above. The region of solid green colour reflects the amount of femoral head that is seated within the socket. Notice how much flatter these femoral heads are, and how much poorer the amount of seating is on this x-ray compared to that of the normal dog hip x-ray. Also notice the areas of roughened bone, with spurs off the top of the socket and extra calcified masses. These regions of extra bone growth indicate degenerative arthritic change. Both the ball and the socket are irregularly shaped and fit together poorly.

Source: http://pointseastwest.com

Understanding hip dysplasia

A ball-and-socket hip joint connects your dog’s femur or thigh bone to his pelvis. The ball, called the femoral head, is part of the femur while the socket or acetabulum is part of the pelvis. In normal hips, the bones match each other perfectly and the ball moves freely inside the socket. The joint is strengthened by a strong ligament that attaches the ball to the socket. The area where the bones touch each other is smooth and protected with cartilage.

Simply defined, hip dysplasia is a poor- fitting hip joint that causes pain for the affected dog. In a dysplastic hip, the ball may be flattened or too small, or the socket too shallow. Dysplastic dogs are likely to develop arthritis and increased joint pain as they get older. One or both hips (called bilateral hip dysplasia) may be affected.

HD: Diagnosis and treatment

Dr Marthinus Hartman takes us through various scenarios for diagnosing, treating and managing hip dysplasia.

Puppy A

At 13 weeks of age, Puppy A is screened for hip joint laxity to determine the possibility of future hip joint problems. Radiographs are of no value at this early age – the vet will use another tool – his or her hands. The puppy may be sedated for the test and the vet will feel for laxity in the hip joints. Two tests are conducted, the Ortolani test and the Barden’s hip lift test. Laxity in the joint is caused by a loose joint capsule and poor muscle tone in the muscles surrounding the hip joint. If laxity is diagnosed, preventative surgery will be advised.

Juvenile pubic symphysiodesis (JPS) is performed on puppies at 16 weeks of age. It may be done earlier, but not later. The purpose of the surgery is to alter the angle of the acetabulum so that the femur head (ball) fits into it better. A new technique developed in South Africa, called a juvenile pubic symphysectomy, can also be performed and is an improvement on the JPS surgery. In this surgery a small part of the ventral pelvis is cut away and this gives even better long-term results than the JPS.

Puppy B

This puppy was not screened at 16 weeks and begins to show some signs of lameness and pain at around nine months of age (average age – eight to 12 months). His owner takes him to the vet for an assessment.

Dr Hartman explains that the pain experienced by the puppy at this stage is caused by micro tears in the joint capsule (soft tissue) and not by bone changes. It is therefore still too early to take radiographs and the vet will complete the same two tests described above. Based on their outcome and manipulation of the hip joint, he or she will diagnose hip dysplasia.

Triple pelvic osteotomy (TPO) surgery is performed on puppies from eight months to one year of age, before any signs of arthritis show up on a radiograph. It is a much bigger surgery than the JPS, but also aimed at changing the angle of the acetabulum. During the surgery three cuts are made in the pelvis and the acetabulum is rotated and realigned. A bone plate and screws are inserted to hold the bone in the new position. If required, both hips can be done together, but your vet may suggest completing the second hip four to six weeks later. The prognosis after surgery is very good and the dog will go on to live a healthy active life.

If the owner of Puppy B chooses not to proceed with surgery, the puppy will remain lame for some time, but after about four months, the joint capsule will thicken and pain and lameness will disappear. The puppy may be pain-free until about 18 months to three years of age when permanent bone changes, colloquially known as arthritis, start to develop. This progresses to osteoarthrosis, which can be seen on a radiograph. These changes are irreversible and the dog’s pain will increase. Puppy B will now require the same surgery as Dog C or medical management like Dog D.

Hip replacement

Dog C

This dog was not assessed as a puppy. He is now just over two years of age and his owner notes various signs of lameness and pain. He sways when he walks and struggles to get up in the morning. At the vet, radiographs are taken and the vet diagnoses hip dysplasia. A total hip replacement is the best option for Dog C.

Total hip replacement (THR) surgery involves the removal of the femoral head and acetabulum. They are replaced with a metallic prosthesis (a ball and cup) covered with high-density plastic. Radiographs of the dog’s pelvis are taken under general anaesthetic before the surgery to accurately measure for the correct size prosthesis – an important step for the success of the procedure. Measurements are made and a correct prosthesis ordered before the day of the surgery. Success rates are high and in most cases the dog will go on to live an active and pain-free life.

Dog D

Hip dysplasia is diagnosed in Dog D, but his owner is unable to afford THR surgery or declines it. The dog’s condition will be medically managed – this includes pain management, supplements and rehabilitation like hydro swimming. (See the box ‘Alternative therapies and lifestyle changes’.)

Medical management can continue for as long as the dog responds to it. Drugs like a non-steroidal anti-inflammatory and opioids (not for long-term use) are used to manage pain. Your vet may also suggest a supplement like glucosamine and chondroitin sulphate to protect and strengthen cartilage. There are many different supplements available on the market and your vet will advise you on what your dog requires.

If the dog no longer responds to medical management, a femoral head and neck ostectomy (FHO) must be considered. This surgery is a salvage procedure to eliminate pain for the dog and not a substitute for a total hip replacement. During surgery the femoral head and neck are removed. Scar tissue will form in the area over time, providing some functionality of the joint. While this is a cheaper option to a THR, the dog owner must understand that its success rate is far lower.

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