Canine Hip Dysplasia (CHD) is a condition that begins in dogs as they grow and results in instability or a loose fit (laxity) of the hip joint (Figure 1). The hip joint laxity is responsible for potential clinical signs (symptoms) of hip pain and limb dysfunction and progressive joint changes. The hip joint is a ball and socket joint and continual abnormal movement of the femoral head (ball) deforms the acetabulum (socket). The long-term response to this joint laxity is the progressive loss of cartilage, the development of scar tissue around the joint, and the formation of osteophytes (bone spurs) around the ball and socket (Figure 2).
The cause of CHD is multifactorial; however, hereditary (genetics) is the biggest single risk factor. Rapid weight gain and growth through excessive nutritional intake can complicate the development of CHD. Hip dysplasia occurs most commonly in large breed dogs.
The symptoms of CHD are lameness (limping), reluctance to rise or jump, shifting of weight to the forelimbs, loss of muscle mass on the rear limbs, and hip pain. Generally, divide dogs with CHD into two groups showing symptoms of CHD:
Group 1: Younger dogs without arthritis, but with significant hip laxity
Group 2: More mature dogs that have developed hip arthritis due to CHD
Dogs may show symptoms at any stage of disease’s development, although many dogs with CHD do not have any obvious symptoms.
CHD is diagnosed by a combination of two methods. Specially positioned hip x-rays and special palpation methods that determine abnormal hip joint laxity, both require light sedation. The most accurate x-ray method at an early age is the PennHIP distraction method. This is a quantitative method that measures the actual amount of hip laxity. It accurately predicts whether a puppy will develop hip dysplasia and what surgical options would be best suited to prevent crippling arthritis (Figure 3). Special training and equipment are necessary to perform this test. PennHIP provides an independent written confirmation of CHD for the pet owner and examining veterinarian. Some primary care veterinarians and many ACVS board-certified veterinary surgeons have taken the training course and have the equipment to perform this test.
The palpation method is called the Ortolani Sign. It has been used in newborn children since 1937 and continues to be the "gold standard" for the early diagnosis of hip dysplasia in newborns around the world. It has been used in young puppies since the 1985 using light sedation. It is not quantitative, but if present confirms that the puppy will usually have hip arthritis by one year of age. Many primary care veterinarians can perform this exam during the early age, 10–16 weeks, vaccination exams. If the Ortolani Sign is not present, there is a false negative possibility that can be resolved by the quantitative PennHIP method.
Unfortunately, the often-used x-ray exam by the Orthopedic Foundation for Animals that most breeders use, is not accurate and predictive of CHD at very young ages. Their recommendation is a preliminary exam at 1 year and the final exam at 2 years of age. This is too late in the progression of CHD because the dogs with crippling arthritis have missed two surgical options (JPS and DPO/TPO, see Treatment) that can significantly reduce the effects of hip dysplasia by 1 year of age.
Risk of complications after JPS are very low; almost all are minor in nature. Success rates for JPS eliminating hip laxity are high and aftercare is very brief, usually just entailing basic incision care and short-term activity restriction.
Reported complications after DPO and TPO include screw loosening, change in limb range of motion, and pelvic canal narrowing. However, the incidence of complications is low and reports of long-term function are expected to be good to excellent.
THR results in an excellent chance of markedly improved limb function. Potential complications after THR include infection, hip dislocation, “loosening” of the implants over time, nerve injury, and femur fracture.
Following both DPO/TPO and THR, the dog’s activity should be restricted to leash exercise outdoors and confinement to a small area indoors until the procedures are deemed healed (via examination and X-rays), generally six and eight weeks respectively. Most pets are weight bearing soon after surgery and require supervision to prevent overuse of the leg during the healing period. If necessary, use a sling for initial assistance with walking. The dog should avoid stairs, slippery surfaces and interactions with other dogs. To get back to normal, slowly increase activity after the initial period of restriction.
Results after FHO vary and are highly dependent upon patient size and proper postoperative physical rehabilitation. While many dogs will have varying degrees of lameness, function should improve when compared with preoperative status. After FHO, pets are encouraged to use the limb as soon as possible in a controlled manner. Aggressive physical rehabilitation and controlled exercise to increase hip range of motion are essential for an optimal outcome. It may take up to six weeks or longer after surgery for some dogs to show improvement.