Diagnosis and Management of Canine Hip Dysplasia

Canine Hip Dysplasia (CHD) is one of the most common causes of lameness and disability affecting dogs. CHD has been proven to be an inherited developmental bone disease. Mode of inheritance is thought to be polygenic and environmental factors influence whether or not the genes are expressed. CHD has proven to be very difficult to eradicate from the canine population because it is impossible with today’s knowledge to accurately identify carriers and therefore to eliminate carrier dogs from breeding programs.

Dogs with CHD are born with normal hips and the first signs of hip dysplasia can be first noted at around 3-4 months of age. Early on dogs will have effusion in the hip joints and hypertrophy of the round ligament. This progresses to laxity in the hip joints at 5-6 months of age with resulting subluxation of the hips. Dorsal acetabular rim microfractures develop leading to remodeling and osteoarthritis of the hips.

Dogs with CHD typically begin showing clinical signs between 5 and 12 months of age. Initial clinical signs will include lameness in the pelvic limbs and gait abnormalities. Some dogs display exercise intolerance and refuse to go on walks or climb stairs. Dogs may have a sloppy gait but never display neurologic deficits and ataxia.

Physical Exam:

The physical exam begins by observing the dog walk. Many dogs will show lameness in one or both pelvic limbs. Gait abnormalities my include range of motion deficits, circumduction of the limbs, bunny hopping, or difficulties in sitting or rising. When examining the hips, pelvic muscle atrophy may be noted and pain is often noted on flexion or extension of the hips. In severely affected dogs, crepitus can be appreciated on flexion-extension or on internal or external rotation of the joint. Subluxation of the hips can be demonstrated with a positive Ortolani or Bardens sign. A complete orthopedic examination should be performed to rule out concurrent orthopedic diseases such as cranial cruciate ligament disease or other conditions of the rear limb. A neurologic exam should be performed to rule out concurrent neurologic disease that may or may not limit the success of treatment for hip dysplasia.

Radiography

The hip joints of the dog are typically evaluated with a standard extended leg ventrodorsal view of the pelvis and hips. Radiographs are best taken under sedation or anesthesia to assure well positioned films. The hip joints are not easily evaluated on poorly positioned radiographs. Dogs with hip dysplasia will exhibit changes in the hip joints that range from simple subluxation to severe osteoarthritis. Radiographic changes tend to be progressive and osteoarthritis will worsen with age. Screening films for hip dysplasia can be evaluated either through the Orthopedic Foundation for Animals (OFA) or Pennhip. OFA requires that dogs be 2 years of age and can be performed either under sedation/anesthesia or awake. Pennhip can be performed as early as 4 months of age and does require at least sedation. Pennhip uses a distraction radiographic technique that is more rigorous in the evaluation than OFA.

Medical management of CHD

Nearly all dogs will begin with medical management of their CHD. Medical management may consist of pharmacologic therapy, weight loss/control, joint supplements or physical therapy. Additionally, there are many alternative/ complementary medical products and procedures that are being promoted for CHD, most of which have little scientific proof of efficacy.

The most effective drugs for the management of CHD are the NSAIDs. There are numerous different drugs on the market and most have been found to be safe for dogs for long term use. All of these drugs are very effective at relieving the pain associated with CHD and all are associated with relatively low rates of adverse reactions. Adverse reactions when they occur may include gastrointestinal upset or ulceration, idiosyncratic liver toxicity or renal dysfunction. While adverse reactions are relatively uncommon, it is recommended that liver enzymes and renal values be monitored periodically on all dogs that are on these medications chronically. These drugs should not be used in dogs with known sensitivities to the drugs or in dogs with known renal compromise.

Nutritional supplements such as glucosamine/chondroitin supplements and omega III fatty acid supplements (fish oil) have been found to have general anti- inflammatory effects and are useful in dogs with CHD. These products are not very potent and may be used in conjunction with NSAIDs. There are few if any side effects of any importance associated with these drugs.

Weight loss in dogs that are over-weight is critically important in the management of all joint diseases including CHD. If a dog is over-weight, simply having the dog lose weight may be as effective as any medical therapy that can be offered. Along with weight loss, physical therapy programs designed to maintain and improve muscle mass and range of motion in the hips may be very helpful as part of an overall treatment plan for dogs with CHD.

There are many alternative and complementary products and procedures that are being promoted for canine hip dysplasia and osteoarthritis in general. Included among these techniques and products are chiropractic, stem cell therapy and cold laser therapy. While future work may show that some of these techniques are useful, the scientific evidence to support most of these techniques is contradictory at the present time. More good quality controlled studies need to be performed before these techniques can be considered to be well proven.

Surgical therapy

Surgery for CHD comes may include Femoral head and neck excision FHO), Triple pelvic osteotomy (TPO), Juvenile pubic symphysiodesis (JPS) and Total hip replacement (THR). FHO is a salvage procedure that can be performed at any age to treat pain in the hips. FHO works best in smaller dogs (<40 lbs) and as dogs get larger, becomes increasingly inconsistent. FHO can have good results as far as pain relief but nearly always leaves a dog with reduced range of motion in the hip joints and rarely will return a dog to a completely normal gait. The chief advantage to this procedure is that it is relatively inexpensive and most people that routinely perform orthopedic surgery can perform it.

Juvenile pubic symphysiodesis is a newer procedure that must be performed on dogs that still have significant growth potential. In most dogs, it is ideally performed at 16 weeks of age or less. JPS fuses the growth plate of the pubis on the ventral midline of the pelvis order to ventrovert the dorsal lip of the acetabulum. Since the pubic bone attaches to the pubis and the ventromedial aspect of the acetabulum, the pubis may be used as a bow-string” to cause ventroversion of the acetabulum thus capturing the femoral head and preventing subluxation. This procedure is relatively inexpensive to perform but has the disadvantage of being very restricted as far as the age of the patient

Triple pelvic osteotomy is a procedure that using three osteotomies of the pelvis to achieve ventroversion of the acetabulum and, thus, capture of the femoral heal. Osteotomies of the ilium, ischium and pubis are performed through 3 separate surgical approaches, the pelvis is then rotated and stabilized using a specially made bone plate. This procedure can only be performed in dogs with good acetabular conformation that have little to no osteoarthritis in the hip joint. TPO is not appropriate in dogs with completely luxated hips. Typically this procedure is performed in dogs at 6-10 months of age. Most dogs will not be good candidates if over 1 year of age. TPO reached the height of popularity 15-20 years ago and is not performed as often in recent years. TPO can have excellent results but the surgeon must be very discriminating when selecting dogs that are appropriate for the procedure.

Total hip replacement surgery is the Cadillac of procedures for dogs with CHD. THR may be performed with cemented or uncemented components or may be hybridized to include a cementless acetabular component and a cemented femoral component. THR can be performed in any dog over 40 lbs as long as the physes are closed (about 1 year of age). There are now mini hip prostheses that allow performance of these procedures in dogs down to 10 lbs of less. The prosthesis is designed to last the life of the dog and success rates are high with experienced surgeons. The chief disadvantage of THR is the high cost and high level of training required for surgeons implanting the prosthesis.