Technical information for veterinarians
What is canine hip dysplasia (CHD)?
Hip dysplasia (CHD or Canine Hip Dysplasia) is characterized by a loose and unstable hip joint. This gives rise to weakness and lameness to the rear quarters, and eventually leads to painful arthritis.
Canine hip dysplasia (CHD) is polygenic and multifactorial, and is closely associated with selection for breeding.
During the degenerative process, the hyaline cartilage that lines the hip joint is damaged. The damage results from the abnormal forces on the cartilage from the deformed hip socket. Small fractures may also occur in the cartilage. Eventually, under enzymatic action, the joint further degrades and the synthesis of proteoglycans is reduced. The cartilage becomes thinner and stiffer, further compromising its ability to handle the stresses of daily movement and weight bearing.
As the problem progresses, more enzymes are released, which affect the precursors to proteoglycans — glycosaminoglycans and hyaluronate. Lubrication is greatly reduced at this stage and the joint fluid is no longer able to nourish the hyaline cartilage. Inflammation is also present. The cycle continues until pain occurs. The body attempts to reduce this pain by attempting to stabilize the hip joint. New bone is deposited both inside and outside of the joint, and along some of the ligaments and muscle attachments to the area. This causes thickening and a decrease in the range of motion.
Etiology of Canine hip dysplasia (CHD)
The breeding of dogs that already have hip dysplasia is one of the primary reasons canine hip dysplasia (CHD) continues. A dog that has canine hip dysplasia (CHD) in one socket is prone to having a problem with the ligaments of the knee in the other leg (anterior cruciate ligament tear).
Many factors promote the onset of canine hip dysplasia (CHD); these include:
- Genetic inheritance of canine hip dysplasia (CHD)
- Overfeeding high protein and high calories
- Excess calcium (usually due to overfeeding)
- Prolonged inactivity and conversely prolonged or intense activity
Symptoms and diagnosis of hip dysplasia
Early diagnosis of canine hip dysplasia (CHD) affords veterinarians the best opportunity to address the problem as soon as possible, thereby minimizing the secondary arthritic changes that can occur in the hips. The following symptoms are indicative of canine hip dysplasia (CHD):
- Rear limb lameness, particularly after exercise.
- Difficulty or stiffness upon rising or climbing uphill.
- A “bunny hop” gait
- Rising using front legs only and dragging rear end.
- Waddling rear limb gait.
- A painful reaction to extension of the rear legs resulting in a characteristic short stride.
- A side-to-side sway of the croup. Tendency to tilt hips down when pressure applied to rump.
- Reluctance to jump, exercise or climb stairs.
A puppy with canine hip dysplasia (CHD) usually starts to show signs between five and 13 months of age.
Symptoms of canine hip dysplasia (CHD) range from mild discomfort to extreme pain when the affected dog uses the hind limbs and will occasionally be seen following prolonged activity or when the dog gets up or lies down. Later in life the signs become more consistent and occur daily regardless of activity levels. Adult dogs that are in severe pain will usually decrease their activity. They are unwilling to run or climb stairs and, with decreased use, the muscles of their rear legs weaken. Some dogs learn to alter their gait and posture, often showing little or no signs of discomfort even when bone changes are severe.
A diagnosis of canine hip dysplasia (CHD) is based on a history of weakness or lameness to the rear legs, physical examination and x-ray confirmation.
After watching the dog walk and performing a general physical examination, an orthopedic evaluation should be carried out in order to determine the best course of treatment for the dog.
Flexing and extending the hip joint will provide some clues. Dogs with canine hip dysplasia (CHD) usually tolerate hip flexion but resent hip extension. Abduction is also painful.
Conditions that may resemble canine hip dysplasia (CHD)
Several conditions may mimic canine hip dysplasia (CHD), making radiography essential for diagnosis. These conditions include:
- Lumbo-sacral spinal problems
- Ruptured cranial cruciate ligament
- Degenerative myelopathy
- Hypertrophic osteodystrophy
X-rays are necessary to confirm the diagnosis and evaluate the severity of canine hip dysplasia (CHD). Positioning of the dog is very important, therefore, it is wise to find a practitioner who is experienced in correct positioning when seeking evaluation.
The most common X-ray view involves extending the legs with the dog on its back, which is the view for X-rays submitted to the Orthopedic Foundation for Animals (OFA) to provide a hip-scoring scheme for canine hip dysplasia (CHD) assessment. Since most dogs with canine hip dysplasia (CHD) will not be able to tolerate this position awake, sedation or anesthesia is usually necessary.
Proper radiographic positioning is very important to accurately evaluate the hips and to determine the best treatment. In young dogs or in very mild cases, joint laxity may be the only detectable abnormality. Later in the disease arthritic changes are seen.
The Orthopedic Foundation of Animals (OFA) uses board certified radiologists to evaluate submitted X-rays. After two years of age, dogs whose X-rays do not indicate the presence of canine hip dysplasia (CHD) are assigned an OFA number and rated as excellent, good or fair. Hips assessed to be dysplastic are rated mild, moderate or severe. There is also an option for the evaluator to state that the films are inconclusive at this time. Preliminary ratings are given for dogs under the age of two. These results are available to the public for breeding purposes.
The University of Pennsylvania Hip Improvement Program (PennHip®), provides a much more objective evaluation of a puppy’s hips by measuring the amount of laxity in the hip joint, thereby determining the likelihood of developing arthritis in those joints as the pet ages. PennHip® measures the passive hip joint laxity (Ortolani sign) under sedation or anaesthesia. This method uses a technique called compression/distraction to determine where the center of the femoral head and the acetabulum coincide. (This measurement is called the distraction index or DI. A DI of .03 or lower may indicate that the animal does not have hip dysplasia; a DI of .07 or above may be associated with a greater incidence of the condition, and a DI between .03 and .07 is an uncertain area.)
Treatment options for hip dysplasia (CHD)
The treatment for canine hip dysplasia (CHD) is geared towards inhibiting further breakdown of the hip joint and decreasing pain. Various medical and surgical treatments are available today that can ease a dog’s discomfort and restore mobility. The type of treatment depends upon several factors, such as the age of the dog, the severity of the problem and financial considerations. Management of the condition usually consists of exercise restriction, body weight management and symptomatic pain management with analgesics and anti-inflammatory drugs.
Analgesic and Anti-inflammatory medications – Ideally, these should only be used for the short term, when necessary to encourage movement. In most cases these medications act simply as painkillers, and should only be used in addition to lifestyle modifications including weight control and good exercise management.
Commonly used analgesics and anti-inflammatories include acetaminophen and various NSAIDs.
For mild to moderate hip dysplasia in dogs, acetaminophen (Tylenol®, Panadol®, Exdol®, etc.) is recommended for pain relief. Acetaminophen can generally be safely combined with anti-inflammatory medications. Too-high doses of acetaminophen can cause liver damage.
NSAIDs help reduce pain and swelling of the joints and decrease stiffness. When taken at a low dose, NSAIDs reduce pain; when taken at a higher dose, NSAIDs can also reduce inflammation. NSAIDs do not prevent joint damage and when used over the long term, may accelerate joint breakdown. Taking more than one NSAID at a time increases the possibility of severe side effects such as ulcers and bleeding. (Special buffered ASA is available for dogs.) The newer sub-class of NSAIDs, known as Cox-2 Inhibitors include Rimadyl® (carprofen), Metacam® (meloxicam) and Etogesic® (etodolac).
Caution: Vioxx®, a cox-2 inhibitor for use in humans, was just removed from the market place due to lethal side-effects related to heart attack, stroke, rhabdomyolysis and kidney failure due to the mechanism of action. This same mechanism of action is present in all cox-2 inhibitors and it would be wise to take this into consideration.
Cortisone reduces inflammation and swelling. For severe pain and inflammation, cortisone is injected directly into the affected joint. This can provide almost immediate relief for a tender, swollen and inflamed joint.
Visco-supplementation is the process of injecting a gel-like substance into the joint. This substance lubricates the cartilage, reducing pain and improving flexibility. Visco-supplementation decreases friction within the joint, thus reducing pain and allowing greater mobility. This method of treatment requires ongoing injections as benefits are only temporary. Substances used in visco-supplementation include hyaluronic acid, or HA (Legend®, Hylartin® and Synacid®), and poly-sulfated glycosaminoglycans (PSGAGS) such as Adequan®.
Surgery for canine hip dysplasia (CHD)
While every attempt is normally made to manage a pet’s pain through lifestyle adjustments and use of anti-inflammatories and painkillers, it may sometimes be necessary for surgical intervention. This is particularly true for older dogs.
Femoral Head Ostectomy (FHO)
In this procedure, the damaged rough-edged head of the femur is removed. The remaining part of the femur forms a false joint with the muscles, ligaments and tendons in the area. Even though this false joint is not as good as a real joint, a significant reduction in pain is the usual outcome. While almost any size of dog can undergo this procedure, it is much more effective in smaller dogs. Obese animals and those with significant loss of muscle do not usually fare as well.
FHO is a fairly simple procedure, yet pets that have this surgery may return to almost normal function. The false joint that results is considerably smoother and allows for walking, running and playing. However, the new false joint is not a normal joint. It may exhibit decreased hip extension; the dog’s gait is different, but the joint is pain free.
Triple Pelvic Osteotomy (TPO)
In young dogs, the preferred surgery is a triple pelvic osteotomy (TPO). Candidates for this surgery must have little to no evidence of arthritis on a hip x-ray and have adequate depth to the affected hip socket/s. The surgery aims to cut the pelvic bones in three places in order to free up the socket and allow its position to be altered so that the head of the femur fits better. The new socket position is secured using a special plate and screws.
By correcting the dysplastic hip early in the dog’s life, further arthritic change is minimized and this should be the only surgical procedure necessary. TPO is usually performed bilaterally, if appropriate.
Total Hip Replacement (THR)
If the hip joint is the problem behind poor use of the hind leg, replacement with an artificial ball and socket offers the best possibility for return to normal function. The standard hip replacement is ideally performed in mature dogs, preferably not less than two years of age. The dog’s bones must be mature enough to hold the implants and reduce the likelihood of further surgeries. In this procedure the neck and head of the femur are replaced with stainless steel or titanium implants.
Unlike the TPO procedure, THR can be used in dogs that have secondary arthritis. Although THR has a high success rate, the surgery must be performed carefully to reduce the risk of postoperative complications.
Some young dogs may have too shallow a socket for a TPO, but are too young to be ideal candidates for a total hip replacement. In such a case, darthroscopy may be appropriate During this operation, a shelf of bone is created over the rim of the socket. This bone fuses in its new position and stops the head of the femur from sliding in and out of the shallow socket.
This is a relatively new surgery, but in carefully selected cases may produce good results.
In all of these procedures, antibiotics are given intravenously at the time of surgery; however, in the case of a total hip replacement, the surgical site is swabbed for the presence of bacteria at the time of surgery to see if bacteria can be cultured. These animals go home with a short course of antibiotics pending their culture results.
Post surgical follow-up:
Following TPO or THR surgery, an animal will require a period of six weeks’ confinement and strict rest.
Dogs that have undergone FHO are a little different in that early physiotherapy should be encouraged. If the dog does not use the leg much following surgery, scarring will restrict range of hip motion and leg function. Passive range of motion exercises help flex and extend the hip following surgery, maximizing its function as soon as possible. Short, slow leash walks are helpful early on. Slow walking more than any other gait will encourage the dog to use the affected leg. Some dogs recover faster than others.
In the case of TPO and THR, most dogs will be using the leg well at six weeks. In dogs that have undergone FHO, full recovery may take a few weeks to a couple of months. (Function will at best be 80 to 85 percent of normal, but the dog will be able to run, walk and play and be pain-free for these activities.)
Dogs with TPO or THR may begin slow leash walks from 6 to 12 weeks, gradually increasing the duration and distance of the exercise. Freedom around the house can be slowly increased, together with access to stairs.
Small animal health options
Bioflavonoids (plant-based, antioxidant substances with the power to protect plant and animal tissues), have been shown in many scientific studies to help the tissues maintain their youthful structure. Antioxidants from green tea (Camellia sinensis) and grapes (Vitis vinifera) have been shown to have particularly beneficial effects and may be employed preventively or therapeutically to help repair damaged tissues. Nutricol® (available to veterinarians as Recovery®SA, is a proprietary formulation containing both these ingredients.*
Recovery®SA with Nutricol® is a proprietary lifestyle supplement that can enhance your pet’s quality of life.* It may be used on its own or in combination with prescribed medications. See the Oct and Dec 2003 reviews of Recovery®EQ in the prestigious Horse Journal