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Canine Hip Dysplasia (CHD)

Like most large, heavy breeds, the Labrador has a problem with Canine Hip Dysplasia (CHD). Canine hip dysplasia has puzzled researchers for the past 50 years. Although certain aspects of this degenerative, sometimes painful condition are now understood (or at least agree upon in theory), much must still be learned about helping afflicted dogs and preventing the increasing incidence of the disease. Originally, the only means at the breeder’s disposal was to look at the dog’s movement in order to judge whether the hips seemed sound. But many dogs with wretched movement never develop hip problems, and dogs with excellent movement can develop degenerative joint disease (DJD) of the hip joint. Hip dysplasia is one of the most over-diagnosed and misdiagnosed conditions.
Hip dysplasia literally means an abnormality in the development of the hip joint. It is characterized by a shallow acetabulum (the "cup" of the hip joint) and changes in the shape of the femoral head (the "ball" of the hip joint). These changes may occur due to excessive laxity in the hip joint. Hip dysplasia can exist with or without clinical signs. It may or may not be bilateral (affecting both the right and left hip joints) .When dogs exhibit clinical signs of this problem they usually are lame on one or both rear limbs. Severe arthritis can develop as a result of the malformation of the hip joint and this results in pain as the disease progresses. Many young dogs exhibit pain during or shortly after the growth period, often before arthritic changes appear to be present. It is not unusual for this pain to appear to disappear for several years and then to return when arthritic changes become obvious.

Hip dysplasia is a developmental condition and is not considered a congenital anomaly.
Dogs with hip dysplasia appear to be born with normal hips and then to develop the disease later. This has led to a lot of speculation as to the contributing factors which may be involved with this disease. This is an inherited condition, but not all dogs with the genetic tendency will develop clinical signs and the degree of hip dysplasia which develops does not alway seem to correlate well with expectations based on the parent's condition. Unlike many other genetic disorders, however, the occurrence of hip dysplasia cannot be traced to a single gene; it is polygenic (caused by many genes). As with other polygenic disorders, environmental factors play a 50% role in the expression and degree of hip dysplasia. Dogs with no genetic predisposition do not develop hip dysplasia.
In recent studies it has been observed that 2 out of 10 puppies born of so called HD-free parents will develop hip dysplasia. The risk increases to 5 out of 10 if one of the parents does in fact have hip dysplasia; 8 out of 10 will risk developing hip dysplasia if both parents are afflicted.

At present, the strongest link to contributing factors other than genetic predisposition appears to be to rapid growth and weight gain. In a recent study done in Labrador retrievers a significant reduction in the development of clinical hip dysplasia occurred in a group of puppies fed 25% less than a control group which was allowed to eat free choice. It is likely that the laxity in the hip joints is aggravated by the rapid weight gain.

If feeding practices are altered to reduce hip dysplasia in a litter of puppies, it is probably best to use a puppy food and feed smaller quantities than to switch to an adult dog food. The calcium/phosphorous to calorie ratios in adult dog food are such that the puppy will usually end up with higher than desired total calcium or phosphorous intake by eating an adult food. This occurs because more of these foods are necessary to meet the caloric needs of puppies, even when feeding to keep the puppy thin. As stated earlier dysplasia is not caused by factors in the environment but they can influence whether a dog develops the disease. In other words, how you raise your puppy won't determine whether or not he is dysplastic, but it can affect when and perhaps if, he begins to develop symptoms. Some of these factors which have been proposed to worsen, but not cause CHD are types of food fed (diets low in protein are best), avoiding excess exercise during puppy hood (i.e. forced running for any distance, pulling weights, mushing, running with owner on bike, etc.), not using calcium supplementation (may increase the bone remodeling). Reduced caloric intake and glucosamine products in immature animals genetically predisposed for hip dysplasia may lessen the pathologic changes associated with hip dysplasia. In a recent study done in Labrador Retrievers a significant reduction in the development of clinical hip dysplasia occurred in a group of puppies fed 25% less than a control group which was allowed to eat free choice. Studies have been done on supplementation with mega doses of vitamin C. These studies showed that dogs receiving the supplements were least likely to develop the disease. Vitamin C is important for the healthy development of bones, muscles and blood vessels. It has been implicated as having a therapeutic role in the treatment and relief of pain associated with hypertrophic osteodystrophy. In more recent years, therapeutic effect of vitamin C has been indicated in treatment of hip dysplasia. Because vitamin C also functions to maintain integrity of connective tissue cells, accordingly, it has been observed to slow down the progression of osteoarthrosis and relieve pain in dysplastic dogs. Breeders for years have used vitamin C as prophylaxis for hip dysplasia in growing puppies. Vitamin C is a fairly safe drug; overdosage, unlike other vitamins, is not possible since any of the drug not used by the body is quickly excreted. In dogs at higher genetic risk of developing hip dysplasia (i.e. offspring of one or more dysplastic parents), vitamin C treatment may serve as a possible conservative alternative to surgical treatment.
In a Norwegian study, leaded by Dr. Geir Erik Berge, a veterinarian of Oslo, 30 mgs/kg of body weight of polyascorbate was given three times a day for six months, to 100 dogs with severe  joint injury, arthrosis, spondylosis, hip dysplasia, older disc–prolapse, muscle atrophy as a result of functional loss, or senile wear–and–tear in support and motion systems. Approximately 77 percent of the dogs treated showed marked improvement after six months, and 32 dogs out of the 45 diagnosed with hip dysplasia were symptom-free after only one week.
Berge concluded that dogs manufacture suboptimal concentrations of vitamin C in some tissues under the stress of certain ailments. He recommended high–dosage supplementation with Ester–C® ascorbate to help correct those deficits (Berge, 1990).

Guided by Berge's success with degenerative syndromes in dogs, Dr. L. Phillips Brown conducted a similar study with dogs housed at the Best Friends Animal Sanctuary in Kanab, Utah, USA. Dr. Brown administered Ester–C® calcium ascorbate, ordinary ascorbic acid, or a placebo twice daily to each group of dogs for three weeks. Response to treatment was graded with the Average Mobility Improvement Score (AMIS), using a four-point scale, with "0" representing no response and "3" representing a very good response. Treatment was then discontinued for three weeks and the groups were crossed over, so that each group received a different treatment. Treatment and scoring were performed two more times in this fashion. When all improvement scores were added up, Dr. Brown found that dogs receiving the Ester–C® ascorbate showed an AMIS score of 1.5, while dogs receiving plain ascorbic acid showed an AMIS score of 0.5. The average score of the placebo was 0.1, indicating that no significant improvement can be expected if no intervention is performed. Dr. Brown concluded that Ester–C® calcium ascorbate was more effective than ordinary ascorbic acid for improvement of mobility difficulties (Brown, 1994a, b, c).

Polyascorbate, like Ester–C® calcium ascorbate or NOW's Ascorbate Mineral-C, is a mineralized form of vitamin C that aids in the absorption and retention in the body’s tissues, and because it has a neutral pH it does not cause gastric upset. Ascorbic acid, the vitamin C we are most familiar with, is too rapidly excreted to be effective, can irritate the lining of the digestive tract, and at the higher dosage recommended will cause the formation of crystals in the urinary tract.
One Norwegian anecdotal study published in England in 1991 concluded that German Wirehaired Pointer, English Setter, Irish Setter, Gordon Setter and Labrador Retriever puppies growing up during the spring and summer had a lower incidence rate of hip dysplasia than puppies growing up during autumn and winter.
Many researchers conclude that early fusion may lead to bone and cartilage deviations which then could predispose the animal to future dysplasia. An important point that these studies illustrate is that it is possible to improve the individual phenotype of dogs whose parents carried the gene for hip dysplasia (genotypically dysplastic).

If clinical signs of hip dysplasia occur in young dogs, such as lameness, difficulty standing or walking after getting up, decreased activity or a bunny-hop gait, it is often possible to help them medically or surgically. X-ray confirmation of the presence of hip dysplasia prior to treatment is necessary. There are two techniques currently used to detect hip dysplasia, the standard view used in Orthopaedic Foundation for Animals (OFA) testing and X-rays (radiographs) utilizing a device to exaggerate joint laxity developed by the University of Pennsylvania Hip Improvement Program (PennHIP). The Penn Hip radiographs appear to be a better method for judging hip dysplasia early in puppies, with one study showing good predictability for hip dysplasia in puppies exhibiting joint laxity at 4 months of age, based on PennHIP radiographs.
The Orthopaedic Foundation for Animals (OFA) evaluated 103.814 Labrador Retrievers, from January 1974 to January 1998. 14.7% was excellent, 13.2% was dysplastic.

When a puppy is 5-7 weeks old, a veterinarian experienced in the Bardens Palpation technique can make a subjective determination of a tendency toward hip dysplasia. Palpation to estimate the amount of laxity of the hip joints is not an accurate method for prognosis; however, it has been observed that puppies having tight hip joints at an early age have a better chance of developing sound hip joints.
The degeneration in dysplastic dogs can be seen on MRI images as early as 16 weeks. The disease is inherited, but is carried in multiple genes, and the normal vs. abnormal genes are not "black and white" but many "shades of gray." Researchers are working to map the "genome" for the dog, so that they will eventually know exactly which genes are abnormal in inherited diseases, like hip dysplasia, and be able to identify dogs who are carriers. Breeders may eventually be able to simply mail swabs of the gums of their breeding males and females to a lab, and find out if they are carriers of hip dysplasia. And you may be able to send in a swab of the puppy you purchase to make sure it is free of the disease and that it's parents are really who they are supposed to be.

The good news about Canine Hip Dysplasia is that most cases can be treated to help eliminate or decrease pain, allowing fairly normal levels of activity. Very few dogs today have to be put to sleep to alleviate suffering. There are always choices to be made, but the vast majority of affected animals can live quite comfortable lives.
Once a determination is made that hip dysplasia is present, a treatment plan is necessary. For dogs that exhibit clinical signs at less than a year of age, aggressive treatment may help alleviate later suffering. In the past a surgery known as a pectineal myotomy was advocated but more recent evidence suggests that it is an ineffective surgical procedure. However, administration of glycosaminoglycans (Adequan Rx) may help to decrease the severity of arthritis that develops later in life.

Pectineus Tenotomy was popular in the early 1970's. The procedure involves cutting a section of the pectineus tendon and / or muscle. We do not know exactly how this process relieves pain, although it does seem to, in some cases. It does not however, affect the amount of arthritis that will form over the years. A disadvantage is that the relief it provides may be only temporary. Although it is still performed by some veterinarians, it is generally regarded as an obsolete procedure.

Surgical reconstruction of the hip joint (Triple Osteotomy of the Pelvis) is helpful if done during the growth stages. For puppies with clinical signs at a young age, this surgery should be strongly considered. It has a high success rate when done at the proper time.
Triple Osteotomy of the Pelvis, in use for approximately 10 years, is the most common "preventative" surgery for treating hip dysplasia. We use the word "preventative" advisedly because the procedure does not prevent dysplasia but can prevent arthritis and therefore the pain caused by hip dysplasia. Candidates for Triple Osteotomy of the Pelvis must be at least 7 months old and have signs of partial dislocation of the hip. It is essential that the femoral head and the acetabulum are normal in shape and that there is no arthritis present. The abnormal finding on an X-ray must be only the painful dislocation. If the joint is allowed to remain as it is, arthritis will most likely form within 6-8 weeks. It is therefore important to have the surgery performed as soon as possible once a diagnosis is made in order to prevent arthritis.
The word Osteotomy means to cut bone. The purpose of the surgery is to set the bone into the socket. This is done by cutting the bone in three places and rotating the acetabulum so that the femoral head rests securely within it. Once the bone is cut, it is held in place with a stainless steel plate and screws or a combination of screws and wire. It is not necessary to remove the plates, screws, or wires.

Dogs that exhibit clinical signs after the growth phase require a different approach to treatment. It is necessary to determine if the disorder can be managed by medical treatment enough to keep the dog comfortable. If so, aspirin is probably the best choice for initial medical treatment. Aspirin/codeine combinations, phenylbutazone, glycosaminoglycosans and corticosteroids may be more beneficial or necessary for some dogs. It is important to use appropriate dosages and to monitor the progress of any dog on non-steroidal or steroidal anti-inflammatory medications due to the increased risk of side effects to these medications in dogs. If medical treatment is insufficient then surgical repair is possible.

The best surgical treatment for hip dypslasia is Total Hip Replacement. By removing the damaged acetabulum and femoral head and replacing them with artificial joint components, pain is nearly eliminated. This procedure is expensive but it is very effective and should be the first choice for treatment of severe hip dyplasia whenever possible.
Dogs in need of Total Hip Replacement must be examined by the veterinary surgeon to rule out any other possible cause of lameness. Often dogs are referred to us for Total Hip Replacement unnecessarily when a knee (stifle) ligament is torn or when arthritic changes in the spine are causing the pain. It is important that we treat the patient and not the X-ray. Just because a dog has arthritis in the hip does not mean that this is responsible for all of its lameness. Additionally, candidates for Total Hip Replacement must be in good health. Any underlying illness or skin infection must be treated before surgery.
In this procedure, the femoral head is cut off at a carefully determined angle, then all tissue is removed from the marrow cavity of the thigh bone. A trial prosthesis is inserted to ensure a good fit. Next, the cartilage and some underlying bone are removed from the socket and holes are made in the bone for cement that will hold the plastic socket. The plastic socket is then cemented in place. The marrow cavity of the thigh bone is also filled with cement, and the prosthesis inserted. Once the cement hardens (in 3-5 minutes) the ball is locked into the socket and the surgical site is closed. An X-ray is taken after surgery. The patient is discharged 2 days after surgery, and the owner's are instructed to follow the same restrictions mentioned for the Triple Osteotomy of the Pelvis. Approximately 60% of my patients walk out of the hospital better than they walked in. 6 weeks after surgery a dog is allowed full mobility.
The success rate of this surgery is 95% or better. Almost every pet owner reports that after 6 weeks the pet "feels better than it has ever felt", "hasn't felt this good in years", or " It's whole personality has changed- it is a happy dog again". Once healing is complete, the patient can return to normal activities, running, jumping, and playing ball. One of our patients is a search and rescue dog. In summary, hip dysplasia if detected early and treated appropriately should result in pain free hips for your pet.

In Femoral Head Excisions, the ball portion of the hip is removed. Because arthritis develops from the ball rubbing abnormally in the socket, removing 1/2 the hip joint, and thus the bone to bone contact, relieves the pain. Once the ball is removed, a piece of muscle or joint tissue is placed between the thigh bone ( femora) and the socket. This causes scar tissue to form which in turn supports the leg.
We recommend Femoral Head Excision for any dyplastic dog weighing 45 pounds or less. A dog in this weight range will regain near normal mobility once it's hip has healed and scar tissue had formed. Larger dogs do not generally respond as well to the surgery; the scar tissue simply cannot support the heavier weight. Although the pain of dysplasia subsides, a heavier dog has less stamina and sometimes carries the affected leg in an awkward fashion. The recovery period for this surgery can be very long, 4-6 months, and uncomfortable. On the positive side, no exercise restrictions are necessary. In fact, the more exercise the patient gets, the quicker the recovery.
If Femoral Excision is called for, we recommend surgery on both hips at the same time. This forces the dog to use both legs immediately. Operating on only one leg at a time necessitates two hospital stays, two surgery's under general anesthesia, and additional expense to the owner. This approach also permits the dog to walk around on three legs and delay healing.

Once the discomfort subsides after surgery, the dogs personality and activity level improve dramatically. We are often told by pet owners that their dogs play and act like puppies again.
In some cases, this surgery may be beyond a pet owner's financial resources. An alternative surgery is femoral head ostectomy. In this procedure, the femoral head (ball part of the hip joint) is simply removed. This eliminates most of the bone to bone contact and can reduce the pain substantially. Not all dogs do well following FHO surgery and it should be considered a clear "second choice".

Hip dysplasia may not ever be eliminated by programs designed to detect it early unless some effort is made to publish the results of diagnostic tests such as the OFA evaluation or PennHIP evaluations, openly. This is the only way that breeders will be able to tell for certain what the problems have been with hip dysplasia in a dog's ancestry.
 
hipnormal.gif (41198 bytes)  
OFA Extended view normal hip		 Here is a nice comparison of two hips.  The one on the  left is a normal hip.  You can see how smooth and round the head of the femur is and how nicely the "ball" fits into the "socket".  A hip with this structure is very unlikely to ever develop arthritis....unlike the abnormal hip on the right.  Here you can see the result of years of irritation resulting from a poor fit, a shallow "socket", and a short neck attaching the "ball" to the shaft of the femur.  This severe arthritis is a result of hip dysplasia. badhip.gif (40593 bytes)  
OFA Extended view bad hip
There are several problems with OFA. Positioning of the hips is critical for an accurate reading, and a great deal of variation is possible. Precision and accuracy are difficult to achieve on a seven point scale that is only a little better than a pass/fail where the reading is subjective. Readings done at an early age have little or no correlation to readings done at later ages. Certification cannot be received until the dog is two years old (one year for GDC). And the biggest drawback is that the predictive value of OFA has never been shown. Some dogs with OFA good develop hip problems, and some dogs with OFA bad never have any troubles at all.
OFA's latest news release contains some good news, but it should be read with a "filter" for fuller understanding. The intertwining of valid and accurate information with some that could be called (by the skeptics) misleading is unfortunate, but not too much of a problem. The announcement that in the 30 years of OFA's existence there has been "dramatic" improvement in dogs' hips must be expanded upon... salted before swallowing.
The opening statement that, "Breeders working with the OFA have reduced HD by 29% and increased the rate of 'excellent' by 56%" is certainly good news, but let's look at it more closely.
Remember that such figures as the 29% above are definitely skewed. As more vets get to see the good breeders' dogs, and X-ray more dogs, they get a little better at reading the films and giving you a better diagnosis or prediction. Some years ago OFA surveyed the readings of private practitioners and found that more than half read the radiographs WRONG... and in both "directions"; i.e., some read good hips as being bad, and some read dysplastic hips as being normal. Some dogs have even been put down as a result of erroneous readings. Don't let vets euthanize a dog unless YOU can easily see the dysplasia on the film and the dog is in obvious, continued or chronic intermittent pain. The skewing of statistics results from more films NOT being sent to OFA because the vet has become more adept at spotting HD, and saving you the OFA reading fee. Thus, the worst hips don't get reported to and recorded by OFA; of the films that DO go in, these are the better hips and naturally the picture will look rosier than before.
The increase in percent graded "excellent" is indeed good news. As OFA executive director Dr. Greg Keller admits, "the decreasing percentage of dysplastic hips can be due to prior screening" (the skew we mentioned), but he also maintains that the "percent-excellent" is a good barometer of progress (WITHIN THAT COMMUNITY REGULARLY USING OFA, REMEMBER). Say, your vet sends only films of normal hips because people aren't paying OFA for confirmation of obvious dysplasia anymore. If those "normals" have more in the "excellent" category than used to be the case, that means his clients are conscientiously selecting for good joints, because the entire spectrum of hip quality has been shifted toward the normal end of the random range.
Thus, more hips are going to fall into the far (best) end of the bell curve and fewer into the really bad end. It is known that breeding selection for normal hips results not only in fewer cases of HD, but also in lower average severity. And this is why we have cause to rejoice: the higher relative numbers for "excellents" is indeed a sign of progress.
Is the rate of progress satisfactory? For some, who use only the best OFA grades (Good and Excellent), probably, but then they have always been the "A and B students" anyway. The average doesn't really apply to those folks any more than average intelligence has much meaning for Mensa members, or average body fat has for the marathon runner. Those leaders in their fields are unaffected by what the hoi polloi do. For breed clubs and the sport in general, perhaps the rate of progress is much too slow.
There are factors which influence the rating of hips. Some temporary physiological and exogenous factors may influence the appearance of hips in radiographs. Among them are the estrus cycle of the female and anesthesia administered for the purpose of taking the radiographs. Fluctuating hormone levels and anesthesia have an effect on pelvic muscles and may cause an increase in visual subluxation of the hip joints. In such a case, a rating may be lowered by these factors.
The OFA method is still the only method used in many European countries. Although this uniformity looks good, results cannot be compared easily, because of the difference in interpretation. For example, some dogs have been evaluated by both the Dutch and the German system. Differences were large: always the Dutch evaluation indicated an inferior result. There are many examples of dogs being rated CHD Free in Germany and CHD Tc or even Mild Positive in the Netherlands. The Netherlands are considered to have the most demanding test of Europe. Fair enough, if the OFA method would be reliable. But it isn't.
One last word about the OFA method: If you use OFA, don't screen dogs below the age of two years and above 5-6 years of age. Below the age of two years it is difficult to draw the line between what is normal and abnormal; above 5-6 years of age, primary arthritis of old age may be impossible to differentiate from slight hip dysplasia.

PennHIP (from University of Pennsylvania Hip Improvement Program) is a closed registry that was developed by Dr. Gail Smith at the University of Pennsylvania School of Veterinary Medicine. In studies of the mechanics of the hip joint, Dr. Smith found that the hip extended view could actually mask some of the hip laxity. He determined that a neutral position, where the hips are positioned as though the dog were standing, best showed maximum laxity. An additional benefit of this position is that it produces a much more consistent reading.

The PennHIP method is a novel way to assess, measure and interpret hip joint laxity. It consists of three separate radiographs: the distraction view, the compression view and the hip-extended view (see below). The distraction view and compression view, developed by Dr. Smith, are used to obtain accurate and precise measurements of joint laxity and congruity. The hip-extended view is used to obtain supplementary information regarding the existence of degenerative joint disease (DJD) of the hip joint. (The hip-extended view is the conventional radiographic view used to evaluate the integrity of the canine hip joint.) The PennHIP technique is more accurate than the current standard and it has been shown to be a better predictor for the onset of DJD.
The radiographs below are of the same dog, yet the hip joint laxities in each view look very different. Notice that the hips in the distraction view appear to be much looser than they do in OFA's hip-extended view.
 

Distraction view (PennHIP)  
Compression view (PennHIP)  
The obvious contrast in joint laxity between the distraction and hip-extended views demonstrates the fundamental difference between the two radiographs. The looser the joint on the distraction view, the greater is the chance that the hip will develop DJD. The tighter the joint, the less likely DJD will occur. The hip-extended view tends to mask true hip joint laxity because the joint capsule is wound up into a tightened orientation when the hips are extended. This explains why measurable joint laxity on the distraction view is always greater than the measurable laxity from the hip-extended view. In fact, distraction laxity is up to 11 times greater depending on the breed of dog under study.

When an older dog is exhibiting signs of pain associated with this condition it is often possible to help them dramatically through medication and simple steps like providing a warm bed or warm spot to rest during the day. There is no advantage to pain and steps should be taken to ensure that the older dog is not in pain. Regular exercise can be very helpful and weight loss can have dramatic effects on the amount of discomfort a dog experiences.

Working with your vet to come to the best solution for your dog and your situation will enable you and your dog to enjoy life to its fullest, despite the presence of hip dysplasia.

For now, the best chance of avoiding the disease is still to select puppies from parents who both have normal hip joints, but this doesn't guarantee the puppy won't have dysplasia. Normal puppies may also be born to parents who have hip dysplasia. Like all of life, it's a crap shoot, but it still pays to get the best odds you can.

Line breeding or inbreeding dogs can actually decrease the incidence of dysplasia in a line. The more inbreeding, the lower the heritability index because inbreeding reduces the total genetic variability, that is, the gene pool is smaller. Inbreeding is not really a bad thing, in fact all purebred dogs are inbred or they would not resemble their breed and would look more like feral dogs. Inbreeding only becomes problematic when undesirable genetic traits are concentrated within the gene pool. This is why a strict culling program along with excellent record keeping is necessary in a breeding program that decides to use this method.
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Hip dysplasia scheme in Great-Britain:
All Labradors, of both sexes, intended for breeding should be X-rayed at not less than one year of age. The British Veterinary Association and the Kennel Club have run a joint scheme (the BVA/KC hip dysplasia scheme) for many years. This is based on hip scoring, and the vet submits the X-ray, bearing the KC registration number of the dog, to the scheme. Each hip is scored from 0 to 54, making a total of 108 maximum between the two hips. The lower the score the better, and 0:0 is the best score possible.
The average combined score for all the Labrador X-rays submitted so far (over 12,300) is 15, and no-one should breed from a dog with a higher hip score than this if HD is ever to be reduced or eliminated from the breed. Anyone buying a puppy should ensure that bath parents have been X-rayed and have achieved a low score. This is not, of course, an absolute guarantee that the puppy will not develop hip dysplasia, but it should considerably reduce the chances.
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