Canine Hip Dysplasia is a disease effecting primarily large breeds but occurs in small breed patients as well. The clinical presentation of CHD is often characterized as bi-phasic with patients having problems between 6 months and 2 years of age and then again at middle to older age. Fundamentally, the disease results from a combination of genetic and environmental factors and requires attention to many issues to prevent, minimize or treat the disease. The mechanism of genetic transfer is polygenetic which means many genes are involved in determining the patient's potential for exhibiting the problems we call Canine Hip Dysplasia. When a patient develops these problems we say the genetic potential has been phenotypically expressed. Typically CHD effects both legs, however approximately 10% of patients will be effected on only one side.

Patient's with CHD often are slow to rise and tire quickly when exercised. Young patients have gait abnormalities when they run often described as "bunny hopping". The underlying problem with CHD is the hip components don't fit together well. This poor fit called "incongruity" results in abnormal stresses which cause pain, dysfunction and arthritis. Osteoarthritis secondary to CHD is our biggest enemy in treating the disease. (Insert normal hips and degenerative hips) Figures

Historically, veterinarians have focused on treating canine hip dysplasia (CHD) medically or surgically. As our knowledge base grows, it is becoming more evident that early intervention is the key to avoiding the high morbidity of canine hip dysplasia. Total hip arthroplasty (replacement) and excisional arthroplasty combined with medical management using NSAID's, PSGAGs (polysulfated glycosaminoglycans) or Slow Acting Disease Modifying Agents such as glucosamine and chondroitin sulfate will continue as our standard armamentarium for treating patients with clinical hip dysplasia.

Recent research has shown there are three interventional actions through which we can significantly impact the developmental component and phenotypic expression of canine hip dysplasia. These intervention actions are puppy nutrition (8 weeks-12 months), pubic symphysiodesis (4-5 months) and triple pelvic osteotomy "TPO"(6 months-12+months). The key to all of these strategies is veterinarian and owner awareness and implementation of appropriate screening protocols.

Screening protocols should be implemented at three points in the puppy's routine care regime. These screening opportunities are often associated with wellness examination, ovariohysterectomy or castration. The first screening exam should occur at approximately 10-12 weeks of age. The patient should be examined for hip laxity utilizing the Barden test or Ortaloni test to detect subluxation of the coxofemoral joints. Stress radiographs should be performed if excessive laxity is identified. The second screening exam should be performed at 16 weeks. If laxity is present, radiographs and referral for pubic symphysiodesis should be considered. The third screening exam is performed at approximately 6 months of age. If laxity is demonstrated then referral for triple pelvic osteotomy is appropriate. At each screening examination, continued re-enforcement of nutritional counseling is vital.

Multiple studies have shown the single best preventive step veterinarians can provide to improve the patient's hip phenotype is nutritional counseling. Each patient should be frequently evaluated to maintain a feeding program that produces a lean body conformation. The best measures of appropriate body weight on an every day basis include the ability to easily palpate the ribs and the presence of tapered waist at the flank fold. This type of monitoring can be taught to the client but is best performed by the veterinarian in conjunction with routine wellness examinations and vaccinations. It is often important to clients that have purchased breeds with high hip dysplasia incidence that their pets reach maximum body size. Accordingly, pet owners should know that caloric limitation to produce the desired rate of growth to prevent phenotypic hip dysplasia does not effect the total growth of the pet. The key point is that the end result is the same. It simply takes longer for the patient to achieve its genetic growth potential.

Pubic symphysiodesis is a new procedure designed to produce a more congruent coxofemoral joint in dysplasia prone individuals which demonstrate hip laxity at an early age. It must be performed between 31/2 to 41/2 months of age for maximum effectiveness. It has been shown to be effective in lab animal species and canines producing statistically significantly greater acetabular coverage angles in controlled studies. The procedure stimulates premature closure of the pubic symphysis utilizing electrosurgical techniques. This alteration results in compensatory lateralization of the acetabulum and a more congruent hip. Technical errors result in failure of the growth plate to close, failure of symmetrical closure or uretheral damage. In patients that would go on to develop congruent hips, the procedure has not been shown to produce unfavorable side effects.

Triple pelvic osteotomy is a surgical procedure shown in properly selected patients to produce excellent long term hip congruity and clinical function. TPO is best performed before any degenerative changes are present in the joint. This typically means the ideal candidate is presented between 6 and 10 months of age. Arthroscopic evaluation of the hip joint is recommended to assess the level of degenerative change prior to TPO. Many patients are still candidates up to 12 months and older but require careful assessment. Important selection criteria include age, hip conformation, degree of degenerative change (arthroscopic evaluation) and client commitment. In TPO the acetabular segment is mechanically repositioned to better cover the femoral head.

Total hip arthroplasty is the best alternative for most adult patients suffering from CHD. We utilize a modular cemented system at STVS and have excellent results in these patients. Post operative care, patient size and compliance, and expense are important considerations in case selection. Excisional arthroplasty is an acceptable alternative salvage procedure for end stage coxofemoral joint disease or in patients for whom other treatments are not available.

Excisional arthroplasty, also known as Femoral Head and Neck Ostectomy (FHO) removes the femur's contribution to the hip joint. (See Figure 1). This allows the top of the femur to be capture by a muscle sling that over time functions as a false hip joint. Results are variable from case to case but many patient's have satisfactory outcomes with this procedure. It requires less post-operative care and is less costly than other surgical treatments.

In summary, there are many ways we can intervene to help our patient's avoid phenotypic expression of canine hip dysplasia or to treat clinically affected patients. Recent studies have provided excellent evidence so that we now have the opportunity to intervene earlier and more successfully than ever before. Veterinarian and owner awareness and early detection of susceptible individuals can greatly improve our record in beating this crippling disease that often leaves our patients with the choice of ineffective medical management or expensive surgical alternatives. The many options require a complete examination and thoughtful assessment of the right plan for each patient.