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Wednesday, May 3, 2017

Canine Hip Dysplasia

Canine Hip Dysplasia

Canine hip dysplasia is a disease that begins in young dogs with instability or deep relaxation of the hip joint (Figure 1). The laxity of the hip joint is responsible for the first clinical signs. Abnormal hip movement stretches the fibrous joint capsule and the ligament that connects the head of the femur to the pelvis, producing pain and lameness. The acetabulum (the hip cavity) is easily deformed by the continuous movement of the femoral head. A microfracture of the acetabular bone may occur, causing more pain and lameness in young dogs. The physiological response of the dog to joint laxity is proliferative fibroplasia or thickening of the joint capsule and formation of new bone or osteophytes at the border of the acetabulum and femoral neck (Figure 2).




Figure 1. Hip dysplasia occurs in young animals as instability of the hip joint. As the dog gains weight, the head of the femur (the “ball”) leaves the acetabulum (the “cavity”) to the degree that the joint capsule and ligament allow it. The joint capsule and ligament are gradually stretched allowing the femoral head to leave the acetabulum even further.




Figure 2. Joint instability causes abnormal cartilage wear. Cartilage wear leads to the formation of osteophytes (bony spurs) and thickening of the joint capsule, which are characteristic signs of osteoarthritis or degenerative joint disease.



These responses help to stabilize the hip joint. New bone formation is visible on radiographs and is considered as osteoarthritis or degenerative joint disease (Figure 3).


Figure 3. Pelvic x-ray of a dog with degenerative joint disease (osteoarthritis) in the hip as a result of hip dysplasia.





Osteoarthritis progresses during the life of the dog. However, radiological signs of osteoarthritis are not always associated with the clinical function.


Causes


The causes of hip dysplasia are multifactorial and include both hereditary and environmental factors. Rapid growth and weight gain caused by excessive nutritional intake may encourage the development of hip dysplasia. Some mild and repeated trauma that causes synovial inflammation (lining of the joints) can also be an important cause.


Incidence and prevalence


The incidence of hip dysplasia is higher in large dogs. Two populations of animals show clinical signs of lameness: (1) patients 5 to 10 months of age, and (2) patients with the degenerative joint disease.


Signs and symptoms


Clinical signs of hip dysplasia include limp, resistance to lifting or jumping, weight loss to the front limbs, loss of muscle mass in the hind limbs, and pain when manipulating the hips. Dogs may show clinical signs at any stage of disease development, although many dogs with hip dysplasia show no apparent clinical signs. Some dogs show pain between 6 and 8 months of age, but recover as they grow. As osteoarthritis progresses with age, some dogs may show clinical signs similar to those of people with arthritis, such as limp after unusual exercise, lameness after prolonged confinement, severe problems if they are overweight.


Risk factor's


The risk factors for CHD are a race (genetic), rapid growth, and excess nutrients.


Some veterinarians recommend taking an x-ray of the hips at 6 months of age to identify dogs with hip dysplasia with sufficient time to perform a triple pelvic osteotomy. In the case of many dogs, owners seek the surgical advice of a veterinarian when the dog has been lame for a regular period and has not responded to medical therapy. Many of the surgical treatments for hip dysplasia are performed by specialist surgeons.


Exams, tests, and images


The physical examination includes an evaluation of lameness and hip palpation. Many dogs have pain when stretching the hip joint by moving the leg back. The standard radiographic view for diagnosing hip dysplasia is the pelvic ventrodorsal view with the hind limbs extended symmetrically and rotated inward to center the patella in the trochlear groove (Figure 3). The dog must be very sedated or anesthetized to rest and be in the proper position. The Orthopedic Foundation for Animals, an agency that detects canine hip dysplasia, will certify a dog after 2 years of age. Stress X-rays can be used for 4 months to detect the susceptibility of the breed to hip dysplasia. An acetabular dorsal border view may be used to define the angle and condition of the acetabular dorsal border in the evaluation of a dog for a triple pelvic osteotomy.


Differential diagnosis


A number of neurological and orthopedic problems cause clinical signs similar to those seen in hip dysplasia. In young dogs, a distinction should be made between hip dysplasia and lameness caused by panosteitisosteochondrosis, and occasionally partial or total cranial cruciate ligament injury. In older patients, pain and lameness associated with pressure on nerve roots in the lower back and lameness associated with cranial cruciate ligament rupture, polyarthritis or bone neoplasia (cancer) should be ruled out prior to attributing clinical symptoms Of hip dysplasia. Many dogs have evident hip dysplasia on X-rays, however, lameness is caused by another problem.


Complications caused by the disease


The main complication caused by hip dysplasia is the development of osteoarthritis or degenerative joint disease. Dogs with unstable hips as a result of hip dysplasia are more likely to dislocate the hip with minimal trauma, for example, they may fall while running in the yard.


Treatment Options


The treatment depends on the age of the dog, the degree of discomfort, the physical and radiographic findings, and the owner's expectations and economic situation. There are conservative and surgical options for young and adult animals with hip pain as a result of hip dysplasia. Conservative or medical treatment is used in most young animals. Although early surgical intervention with juvenile pubic sinfisiodesis or triple pelvic osteotomy may improve the prognosis of acceptable long-term clinical function, approximately 75% of conservatively treated young patients regain acceptable clinical function at maturity. The remaining 25% need medical or surgical treatment at some point in life.


In puppies younger than 20 weeks, juvenile pubic sinfisiodesis (SPJ), a technique to stop the growth of the pubis (part of the pelvis), can be performed with the aim of modifying pelvic growth and increasing the degree of Coverage of the acetabulum over the femoral head. Most pups at this age do not show clinical signs of hip dysplasia, so the diagnosis depends on the use of a screening technique to document hip laxity, such as Penn Hip, which determines which animals can be Candidates for the procedure. Although specific criteria for the application of SPJ have not been developed, puppies younger than 20 weeks of age who have palpable and radiographic evidence of hip laxity may be considered fit for the procedure.



Young dogs (less than one-year-old) with deep hip relaxation, but no arthritic changes, can be treated with a pelvic osteotomy (also sometimes called triple pelvic osteotomy). This procedure involves cutting the pelvic bone in three places and turning it to stabilize the hip joint and in many cases slow the progression of osteoarthritis. (Figure 4).


Figure 4. Pelvic x-ray of a dog after a triple pelvic osteotomy. The purpose of this surgery is to create an acetabulum (cavity) deep enough so that the femoral head no longer leaves the cavity when the dog gains weight.



Young dogs with osteoarthritis will not benefit from this procedure and will be treated medically as needed. Veterinary advice should be sought to treat pain and lameness with non-steroidal anti-inflammatory drugs (NSAIDs). Concurrent treatment with a nutraceutical agent may also be recommended.


Adult dogs with hip dysplasia that show no clinical signs do not require medical or surgical treatment. These dogs should be thin and practice moderate and consistent exercises to develop good muscle mass that supports the hips. Adult dogs with occasional lameness can be treated with nonsteroidal anti-inflammatory drugs and rest. If lameness can be associated with a particular activity, it is better to avoid activity. Once the lameness decreases, a consistent exercise program should be established slowly. If lameness is repeated, exercise should be reduced and medications are given again. Every effort should be made to keep the dog thing. Ideally, the ribs should be easily felt. In obese dogs, only weight loss can relieve clinical symptoms. When medical treatment does not provide pain relief and reasonable function, the dog is a candidate for one of two surgical procedures to reconstruct the hip joint. Femoral head and neck osteotomy consist of removing the femoral part of the hip joint. (Figure 5). The joint is recovered with fibrous tissue and in many cases allows a life without pain.


Figure 5. Pelvic x-ray of a dog after a femoral head osteotomy. The purpose of this procedure is to eliminate contact between the bones of the degenerating hip joint and allow the formation of a pseudoarthrosis (false joint) with healing tissue that results in less pain.


Total hip replacement (RTC) consists of replacing the hip joint with a metal and polyethylene prosthesis (Figure 6). This procedure allows recovering the normal functioning of the extremities in large dogs. The procedure is expensive because of the implants and technical requirements of the surgery and requires a commitment from the owners in the follow-up care.


Figure 6. Pelvic x-ray of a dog after total hip replacement (RTC). The purpose of this procedure is to replace the cartilage of the acetabulum (cavity) with a polyethylene implant, and the femoral head with a metal prosthesis. Most dogs recover excellent function after a total hip replacement.


Possible Complications After Surgery


The risks of complications following juvenile pubic sinfisiodesis are low and failure of the procedure to reduce hip subluxation does not prevent surgical treatment in the future.


Complications reported after pelvic osteotomy include implant failure, loss of abduction of the limb, and narrowing of the pelvis. However, the incidence of complications is low and reports of long-term clinical function are good to excellent.


The results after the osteotomy of the femoral head vary. The prognosis depends largely on the patient size and postoperative physical therapy. In large patients, 50% of animals have a good or excellent function. The rest of dogs have varying degrees of lameness, but the function usually improves compared to the preoperative state. Middle and small patients usually have a good or excellent limb function.


The result of total hip replacement is the excellent recovery from normal function unless complications occur. Complications following total hip replacement include infection, hip dislocation, and fracture.


Follow-up of surgical patients


After a pelvic osteotomy, the dog's activity should be restricted to strap exercises until the osteotomies are cured, usually 6 weeks. Most patients gain weight soon after surgery and should be confined to avoid overuse of the leg during the healing period.


Following the femoral head and neck osteotomy, patients should use the limb as soon as possible. Physical therapy and controlled exercise to increase the range of motion of the hip are essential for optimal outcome. It may take 6 or more weeks after surgery for some dogs to show improvement.


After a total hip replacement, most feel comfortable enough to use the leg as the prostheses stabilize with bone cement. Many dogs will be active quickly and should be confined to a small area with activity restricted only to walking on a leash. The dog should avoid ladders, sliding surfaces, and interactions with other dogs. If all goes well, after 4-6 weeks, you can slowly increase activity until you reach normally.



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