Simran Josan
III Professional year- B.V.Sc.&A.H.
College of Veterinary Science & A.H., DUVASU
An Overview:
Hip dysplasia. Two words that terrify large and giant breed dog owners, but the truth is hip dysplasia can develop in a dog irrespective of its size or breed. This painful condition can drastically reduce a dog’s quality of life and is equally difficult for owners to watch.
Hip dysplasia is a multifactorial abnormal development of coxofemoral joint in dogs that is characterized by joint laxity and inexorably leads to degenerative joint disease. The pathophysiological basis for hip dysplasia is a disparity between hip joint muscle mass and rapid bone development. As a result, coxofemoral joint laxity or instability develops and subsequently leads to degenerative joint changes including acetabular bone sclerosis, osteophytosis, thickened femoral neck, joint capsule fibrosis and subluxation or luxation of femoral head.
Hip dysplasia is hereditary and is especially common in larger dogs, like the Great Dane, Saint Bernard, Labrador Retriever, and German Shepherd. Factors such as excessive growth rate, types of exercise, and improper weight and nutrition can magnify this genetic predisposition.
Some dogs begin to show signs of hip dysplasia as young as four months of age. Others develop it in conjunction with osteoarthritis as they age. In both cases, there are a few symptoms that owners should be familiar with including “bunny hopping” gait, decreased range of motion and crepitation, pain during full extension and flexion,among others.
Diagnosis
The diagnosis of hip dysplasia is commonly practiced but frequently misunderstood. An evaluation for hip dysplasia is based on history, physical examination, radiographic examination, and manual tests on the dog’s hips. The most common techniques used are:
- Ortolani test: Coxofemoral laxity is the hallmark of hip dysplasia in young dogs. This laxity can be assessed clinically by a common physical manipulation known as the Ortolani test. Previously considered as the gold standard, it has been used in veterinary practice since 1985 with the use of light sedation. The dog is placed in lateral recumbency; the examiner stands behind the animal and grasps the upper stifle firmly putting the hip in a neutral position and the femur parallel to the surface of the examination table. A proximally directed force is applied to the shaft of the femur to elicit hip subluxation, while the pelvis is supported with the other hand. Then the stifle is slowly abducted to reduce the hip joint. Hip joints are considered to exhibit a positive Ortolani sign when a palpable or audible ‘clunk’ is present during hip joint reduction. If a ‘clunk’ cannot be elicited, the result of the Ortolani test is considered negative. A positive Ortolani test suggests excessive laxity, but its absence does not always indicate a tight hip. Fibrosis and thickening of the joint capsule, and the acetabular rim and femoral head destruction prevent the detectable clunk.
- OFA Hip Radiographs: The radiographs by the Orthopaedic Foundation for Animals (OFA) has been used for many years to help diagnose dogs with abnormal or dysplastic hips. For this procedure, one radiograph is taken of the dog’s hip in a standard extended hip position. Sedation is not required. The radiographs are subjectively reviewed and given one of the seven “grades”. The grades are Normal (Excellent, Good, Fair), Borderline and Dysplastic (Mild, Moderate, Severe). 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 some important surgical options that can significantly reduce the effects of hip dysplasia by 1 year of age.
- PennHIP Method:The most accurate x-ray method at an early age is the PennHIP (University of Pennsylvania Hip Improvement Program) method. This is a quantitative method that measures the actual amount of hip laxity. In simpler terms, hip laxity refers to the degree of looseness of the femur ball in the hip socket when the dog’s muscles are completely relaxed. It accurately predicts whether a puppy will develop hip dysplasia and what surgical options would be best suited to prevent arthritis. PennHIP radiographs can be done as early as 16 weeks of age allowing early identification and intervention. To obtain diagnostic radiographs it is important that the patient and the surrounding hip musculature be completely relaxed. For the comfort and safety of the animal this requires general anaesthesia. Typically, three separate radiographs are made during an evaluation: the distraction view, the compression view, and the hip-extended view.
- Compression View
One of three radiographic views taken during a PennHIP evaluation. During compression, the femoral head is pushed fully into the acetabulum. This view is included for purposes of accurately indicating hip landmarks and to demonstrate joint congruity – how well the femoral head fits into the acetabulum,
- Hip Extended Position
The hip extended position is included for purposes of evaluating the hips for existing degenerative joint disease. It is not a reliable position for showing true passive laxity.
- Distraction View
. Dogs are heavily sedated or under general anaesthesia. A special “distraction device” is placed between the legs with the dog on its back. The device acts as a fulcrum to apply a harmless lateral distractive force to the hips. The legs are positioned to optimize the measurement of passive laxity. The amount of hip laxity is quantified using the distraction index.
- Distraction Index (DI)
DI is a measurement of maximal passive hip laxity. It is a unitless number between 0 and 1. The distraction index is an indication of the “percent out of joint” that the femoral head is displaced from the acetabulum. For example, a DI of 0.15 means that the head of the femur is 15% out of joint. A smaller number DI means less laxity (tighter hips) and less susceptibility for degenerative joint disease.
Treatment
Treatment is dependent on many factors including age, weight, degree of hip laxity, lifestyle of the owner and their tolerance for the cost incurred. Both surgical treatments and medical management are available for dogs with hip dysplasia. In general, treatment for hip dysplasia focuses on using surgery to preserve the hip function and reduce pain. An early diagnosis of hip dysplasia provides more options for treatment.
- Surgical Treatment
- Treatment option 1: Juvenile Pubic Symphysiodesis (JPS) -Puppies as early as 10 weeks old can be diagnosed with abnormal joint laxity accurately and treated surgically by this procedure.JPS is a minimally invasive surgery that closes the pubic symphysis prematurely by application of heat using an electrosurgical probe. This results in selective growth of the pelvis and acetabulum increasingly covering thefemoral head as the puppy grows during the following 4–6 months. Patients may be able to go home the same day after this procedure.
- Treatment option 2: Double or Triple Pelvic Osteotomy (DPO/TPO)– DPO/TPO is another option for immature dogs (ideally less than 8–10 months old) with CHD but no visible radiographic arthritic changes. These surgical procedures involve cutting the pelvic bone in two (DPO) to three places (TPO) and rotating the segments to improve coverage of the ball by the socket and decrease hip laxity.
- Treatment option 3: Total Hip Replacement (THR)– Total Hip Replacement (THR), the third surgical option, can be used in young dogs who cannot be successfully treated with JPS or DPO/TPO surgeries. They must be managed medically until they are mature enough for THR, at least a year old. This surgical procedure eliminates hip pain by reproducing the mechanics of a normal hip joint with a more natural range of motion and limb function. THR involves replacement of both the ball and socket with metal and polyethylene (plastic) implants. These components are fixated in place with bone cement, metal pegs, or “press fit” (bone ingrowth) methods.
- Treatment option 4: Femoral Head Ostectomy (FHO)– The last surgical option to alleviate the pain secondary to severe hip laxity/dysplasia is femoral head ostectomy (FHO) surgery. FHO surgery can be performed on young and mature dogs. The surgery involves cutting off the femoral head, or “ball,” of the hip joint. This results in the body creating a “false” joint that reduces the discomfort associated with hip dysplasia. While FHO does not recreate normal hip function, it can be a successful pain management strategy.
- Medical Management: Non-operative treatment may be chosen in very mild dysplasia with minor symptoms, or when the owner declines any surgical intervention or if it is simply the matter of cost. Medical therapy for the treatment of coxofemoral osteoarthritis is largely considered palliative. Non-operative therapies designed to decrease pain includes:
- Maintenance of minimal body weight.
- Limited exercise routine i.e. leash walks of a length the dog tolerates comfortably.
- Daily or intermittent use of non-steroidal anti-inflammatory drugs (NSAIDs) such as Carprofen, Robenacoxib, Firocoxib. These drugs areremarkably effective in relieving pain. However, NSAIDs can have significant side effects that if used daily must be monitored with blood tests to avoid kidney and liver damage. If the maximum daily dose is required, the risk of side effects is greater, and the cost of the drug and monitoring can exceed the cost of surgical intervention if the dog is young or middle aged. In severe, painful cases, opioids such as Tramadol – a narcotic pain reliever can be used.
- Cartilage protective supplements are often recommended.
- Physical therapy can be helpful in dogs who lead a very sedentary lifestyle because the owners work long hours. Joint movement and muscle strength help keep them comfortable and more mobile. Physical therapy is also used for dogs undergoing surgery for CHD. This helps strengthen the muscles and increases the speed of recovery.
The goal of medical therapy is to reduce the clinical symptoms of pain, maintaining joint function and potentially changing the joint environment to slow the degenerative process. Other holistic options like hydrotherapy, acupuncture, massage, or laser treatment can also be used for conservative management of hip dysplasia.
In conclusion, the expression of this developmental disorder is influenced by a multitude of factors. Gait analysis, palpation, and radiography are indicated to establish a correct diagnosis, but the incipient disease may be difficult to identify because interpretation of the aforementioned diagnostic techniques can be subjective and requires a great deal of skill and expertise for accuracy. Fortunately, a variety of treatments options are available to help alleviate the dog’s pain.
Hip dysplasia is a distressing condition for both the dog and the dog parent. With the rightoutlook, treatment, and management, it can often be managed successfully and allow for a healthy and happy life for your pooch because as they say, “A healthy dog is a happy dog”.
