Elbow dysplasia is a general term used to identify inherited polygenic diseases of the elbow in dogs. Three specific etiologies make up this disease and they can occur independently or in conjunction with one another. These etiologies include:
1.Fragmented medial coronoid process of the ulna
2. Osteochondritis of the medial humeral condyle
3. Ununited anconeal process
The clinical signs involve lameness which may remain subtle for long periods of time. No one can predict at what age lameness will occur due to a large number of genetic and environmental factors such as degree of severity of changes, rate of weight gain, degree of exercise, etc. Affected dogs may not show obvious lameness and may only have an abnormal gait. Range of motion in the elbow is also usually decreased. Frequently, there is bilateral disease but unilateral elbow dysplasia is not uncommon. Once it is diagnosed, conservative therapy can be an option for dogs affected by intermittent and/or mild degrees of lameness. The use of pain relievers/anti-inflammatory agents such as Aspirin, EtoGesic or Rimadyl can be used during bouts of lameness especially an hour or so before known periods of exercise. Various osteoarthritis modifying agents and nutraceuticals now on the market would be another option such as Adequan, Cosequin, SynoviCre, Glycoflex, Arthramine, and MaxFlex Pet. The use of these drugs should be tailored for the individual dogs improvement note. If side-effects occur or there is persistence of obvious lameness, change the therapy to a different drug from the above choices. You may notice obvious improvements this way. With oral nutraceuticals, the dog may have to have taken the medication for an extended period of time before benefits are noted. It is important to keep your dog as lean as possible to reduce concussive mechanical forces across the diseased joints. Also, to maintain the range of joint motion, strengthen surrounding muscles to improve joint stability and improve the health of the joint fluid, non-weight bearing forms of exercise such as swimming or low weight bearing exercise with leash walking should be done on a regular basis.
If the dog is showing a continuous and severe pattern of lameness, arthroscopic or surgical exploration of the joint is recommended because usually in these cases, significant pathology is more likely to be found and there is also more of a possibility for postoperative improvement. Surgically, to remove joint fragments, the best treatment option would be arthroscopic surgery however, this is not readily available except at some veterinary teaching colleges and private practice surgical referral hospitals.
Arthrotomy where an actual incision is made into the joint capsule is the most common surgery performed however it is more invasive. Studies comparing surgical arthrotomy treatment with non-surgical treatment have repeatedly shown that the incidence of lameness is the same in both groups. Some studies have shown that the severity of lameness is reduced in surgically treated dogs, but radiographic progression of osteoarthritis occurs irrespective of the treatment given. Future studies will most likely show a much more favorable outcome with the use of arthroscopic surgery. A more rapid return to normal joint function has been clinically reported by most owners.
The outcome or prognosis elbow dysplasia depends on the degree of severity of elbow dysplasia and the degree of severity of secondary degenerative joint disease (osteoarthritis). Dogs with severe degenerative joint disease are more likely to have occasional bouts of lameness even after surgery. Overall, the outcome for full return to normal is guarded. Clinically, prognosis has been better in dogs that have had arthroscopic surgery performed early in the course of the disease. With regular surgery where the joint is opened with an lygenic variation is determined by the addition or combination of factors. In additive heredity, traits become more evident according to the number of genes present. Non-additive heredity does not depend some much on the number of genes but rather their combination. The results which have been obtained through selection against hip dysplasia and elbow dysplasia point to the important role played by additive gene inheritance. The phenotype of an animal is its physical appearance. The phenotype with regard to the traits of hip and elbow development is found in dogs and cats by radiographing the hips and elbows and evaluating the type of conformation present. With basic genetics regarding any polygenetic trait, it is important to know the equation: P (phenotype) = G (genetics)+ E(environment).
This equation expresses that the variation in hip and elbow conformation phenotype (represented by excellent to severely dysplastic from the OFA hip scoring method and normal to grade 1, grade 2 or grade 3 elbow dysplasia) comes about from the complex interaction of the animal's own inherited genotype with the environment to which it has been exposed. Quantitative hereditary characteristic traits for hip and elbow dysplasia are influenced in various degrees by environmental factors. Overweight, excess of protein and energy rich food, rapid growth rate, excess exercise or lack of excercise, high calcium intake and other dietary influences have been suggested. Without genetic pre-disposition however, environmental influences alone will not create hip or elbow dysplasia (this goes back to the P=G+E equation).
In order to achieve rapid genetic progress with the use of hip and elbow conformation phenotypes, heritability estimates can be calculated. Heritability estimates are statistically determined (usually through mid-parent offspring analysis statistical methods) and express the reliability of the phenotypic value (radiographs) as a guide to the breeding value of the animal. Heritability measures the relative . This also increases the accuracy in predicting the animal's breeding value and identifies carrier animals.
If the heritability estimate is between 0.4 and 1.0, it is generally considered high and the animal's phenotype is a good predictor of its genetic makeup and rapid results are obtained with genetic selection for or against any trait. This information can be complex to understand without detailed training in genetics. However, the concept is important with regard to providing an indication to an animal's potential reproductive potency based off the heritability estimate of hip dyplasia and elbow dysplasia usually being in the moderate to high range.
An important question that usually arises with regard to genetics of hip conformation is which mate has the most influence on the offsping's hip conformation the sire or dam? Studies looking at progeny hip scores for both the sire and dam show there is approximately the same equal effect. A worse offspring hip conformation will occur as the hip conformation of the dam and the sire worsen. Overall, the transmission of hip dysplasia to the offspring depends on the dam as well as the sire. This would also apply to elbow dysplasia. On the other hand, sire's with many high awards obviously have a far greater influence on the breed than dams and selection of an appropriate sire is more critical because they have the potential for more offspring, therefore more impact on the phenotypic measurement of hip conformation and frequency of elbow dysplasia than a dam.
With regard to genetics of hip and elbow in a breeding program, dogs without canine hip dysplasia and without elbow dysplasia are more likely to be born to parents without hip or elbow dysplasia. It is generally accepted that if two litter mates with similar genetics from a strong pedigree are used in a breeding program and one is rated excellent and the other rated fair, the parent will commonly produce the majority of offspring with hip conformation's similar to their own hip conformation. A small percentage of the offspring may have less superior hip conformation than the parents and another small percentage will have superior hip conformation than the parents. This is expected with any polygenetic trait whether it be hips, size, speed, movement etc. Likewise, numerous reports show that many offspring from parents with hip or elbow dysplasia also become dysplastic, often several or all siblings in a litter are dysplastic. Research performed by Willis summarized results of a number of breeding programs and concluded that in various dog populations, between 64 to 81% of the progeny of normal dogs (as determined on the basis of standard hip conformation scoring) would also be normal and between 19 and 36% would be dysplastic. On the other hand, between 17 and 37% of the progeny of dysplastic dogs would be normal and between 63 to 93 % would be dysplastic. Even with using a dysplastic dog that has a strong pedigree for normal hips, over the course of a few generations, there are higher percentages of dysplastic dogs. Even if the first generation offspring is phenotypically normal from this type of mating, there is increased frequency of dysplastics in subsequent generations due to an increase in the number of carriers in the litter that when breed, go on and pass undesirable traits for hip dysplasia onto their offspring. This is why the OFA does not recommend the use of dysplastic animals in any breeding program no matter what type of pedigree they come from.
The most important information to answer in any breeding program is what is an animal's predictive breeding value? This value can usually be ascertained by the available information present on hip and elbow status of the individual dog, the dog's parents and the dog's littermates. All three of these questions are important with the heritability of canine hip dysplasia and elbow dysplasia being in the moderate range in most dog populations. Unfortunately, all of this information is usually not available since most animals in a litter are not radiographed for hip or elbow conformation. When looking at the order of importance of hip and elbow information on a pedigree analysis and ranking them with regard to placing a predictive breeding value for an individual dog, the dog's parents hip and elbow information is very important followed by the dogs own individual hip and elbow conformation then followed by litter mate information. With most breeders making their predictive breeding value decisions on individual hip and elbow phenotype scores, a decreased frequency of dysplasia will be substantial but slow. Information on parents and siblings makes it more feasible for the breeder to apply greater selection pressure against dysplastic traits and achieve more rapid reductions in the frequency of canine hip dysplasia and elbow dysplasia in their lines. An example would be looking at two potential new sires from different pedigrees to use in a breeding program. Each sire has similar desirable traits that are above average when compared to other members of the breed. The only difference is one sire has excellent hips but has only one parent with an OFA hip number of good (the other did not have an OFA number) and no siblings with OFA hip numbers and one known dysplastic sibling. The other sire has fair hip conformation out of two OFA good parents and 2 OFA good and 2 OFA excellent littermates. The probability for normal hips would most likely be with the use of the fair sire especially when bred to an excellent or good mate that has a similar strong pedigree for hip conformations. When the breeder has all of the information to work with, a higher success rate for hip and elbow conformation is achieved more rapidly.
Unfortunately, with no genetic test available at this time for this inherited complex polygenetic disease, there are no 100% guarantees when breeding two dogs with radiographically normal hip conformation. The radiograph tells you about the phenotype (physical) of the dogs hip conformation but does not always reliably predict the dogs genotype of the hips. The radiographic hip conformation of the dogs siblings (pedigree breadth), parents (pedigree depth) and parents siblings are even more important than the dogs own individual hip conformation. Unfortunately, some breeders place too much emphasis on an individual dog's hip conformation. It is important to realize that a dog with a fair hip conformation from a litter of siblings with all good and excellent hip conformations would be a better choice in terms of the genetic probability of producing normal offspring versus a dog with an excellent hip conformation coming from a litter with a large percentage of dysplastic siblings.
This dog with the excellent hip conformation has a higher genetic probability of being a carrier for hip dyplasia and therefore, a higher genetic risk for producing dysplastic offspring.
Carriers are dogs that phenotypically have normal hips (fair, good and even excellent grades) but genotypically have CHD genes on their chromosomes. As a rule, when two carriers are mated, these genes get passed on to a variable percentage of the offspring causing the phenotypic expression of CHD. The percentage of the litter affected and degree of severity of CHD is variable. These carrier dogs have a percentage of phenotypically CHD affected siblings. The only way to identify them at this time without the availability of a genetic test is to radiograph entire litters. This can be difficult for some breeders since most dogs in a litter end up in pet homes versus show or breeding and information on their hip conformation is usually not available. This limited information makes the existence of carriers unknown in a particular breeding combination. A way to obtain this valuable information is through breeder contract agreements with new dog owners where radiographs are performed on their animals and submitted to the breeder so that entire litter discounts can be obtained when evaluating radiographs of each dogs hip conformation. The OFA discounts are $60.00 for entire litter 2 year old evaluations (3 or more) and $30.00 for entire litter preliminary evaluations (3 or more).
Fortunately, the chance that a dog with a radiographically normal hip conformation actually has a better (more normal) genotype is greater than a dysplastic genotype. Therefore, genetic progress can be achieved with a decreased incidence of CHD through individual preventative hip screening but it is slower when there is no information about the siblings hip conformation.
When looking to buy a puppy from a particular breeder, pedigrees should be obtained with information on the sire, dam and other relatives registration numbers. Using the OFA web, explore only the litter number. If no information is available assume they went to pet homes or were dysplastic. The OFA website address is www.offa.org. A copy of the pedigree can also be sent to the OFA by mail or fax and the percentage of related dogs in the pedigree with OFA numbers can be documented. This information in the OFA's database can be used as a tool for selection pressure to increase the genetic probability for a normal hip conformation when choosing dogs for breeding, competition or a healthy pet. Overall, if there are a lot of relatives that do not have OFA numbers in the pedigree, they should be assumed to be dysplastic until proven otherwise in OFA's opinion and there is a greater genetic risk of obtaining a dog that is dysplastic or a carrier. Overall, the more breeding dogs in a pedigree with OFA numbers and the greater percentage of their siblings in a litter with OFA numbers, the better the genetic probability for healthy dysplastic-free puppies for a given breeding. If this is evaluated over 2 to 3 generations, the incidence of CHD can be significantly reduced with future breedings.
Other important questions to ask a breeder are whether or not this is a repeat breeding, is this a line breeding or is this an outcross breeding. With repeat breedings, you may be able to get information on puppies out of the previous litter especially if the breeder is willing to give you names of people to contact who purchased previous puppies from the mating. If an experienced breeder is running a closed line breeding program, the breeder usually has more knowledge therefore "control" over what good and bad genes are present in their lines. Hopefully, if the breeder has been breeding long enough, the bad genes have been reduced or eliminated altogether. Usually, a breeder who breeds dogs with line breeding hardly ever have problems and if genetic problems occur in puppies, it is usually when the breeder has gone to an outcross breeding with a mate from a different kennel or breeding program. With outcross breedings, it is very important to study the pedigrees of the mate being outcrossed. It may be helpful to contact a local breed club for references of good breeders in your area.
If you end up with the bad misfortune of owning a dysplastic dog, here is some information on management: Hip Dysplasia is a terrible genetic disease because of the various degrees of arthritis (also called degenerative joint disease, arthrosis, osteoarthrosis) it can eventually produce leading to pain and debilitation. The very first step in the development of arthritis is hyaline cartilage damage (the type of cartilage lining the joint) due to the inherited bad biomechanics of an abnormally developed HD joint. Traumatic articular fracture through the joint surface would be another way cartilage is damaged. With cartilage damage, lots of degradative enzymes are released into the joint. These enzymes degrade and decrease the synthesis of an important constituent molecule that forms hyaline cartilage called proteoglycans. This causes the cartilage to lose its thickness and elasticity which are important in absorbing mechanical loads placed across the joint during movement. Eventually, more debris and enzymes spill into the joint fluid and destroy molecules called glycosaminoglycan and hyaluronate which are important precursors that form the cartilage proteoglycans. The joint's lubrication and ability to block inflammatory cells are lost and the debris-tainted joint fluid loses its ability to properly nourish the cartilage through impairment of nutrient-waste exchange across the joint cartilage cells. The damage then spreads to the synovial membrane lining the joint capsule and more degradative enzymes and inflammatory cells stream into the joint and then the first signs of pain appear. In an attempt to stabilize the joint to decrease the pain, the animal's body produces new bone at the edges of the joint surface, joint capsule, ligament and muscle attachments (bone spurs). The joint capsule also eventually thickens and the joint's range of motion decreases.
No one can predict when or even if a dysplastic dog will start showing clinical signs of lameness due to pain. There are multiple environmental factors such as caloric intake, level of exercise and weather that can affect the severity of clinical signs and phenotypic expression (radiographic changes). There is also no rhyme or reason as to the severity of radiographic changes correlated with the clinical findings. There are a number of dysplastic dogs with severe arthritis that run, jump, and play as if nothing is wrong and some dogs with barely any arthritic radiographic changes are severely lame.
Unfortunately once osteoarthritis is present on a radiograph, these changes are irreversible and usually continue to progress over time. If a dysplastic dog has secondary arthritis and pain, most owners elect to first treat their dog with medical management. The key to medical management of arthritis is weight control and exercise management. Studies have shown that a number of dogs with arthritis secondary to CHD or any of the other developmental joint disorders are able to function and live comfortable quality lives with conservative management. With weight control, the goal is to prevent the dog from becoming overweight to reduce mechanical stresses applied to the hip joints. In general terms, the ribs should be easily palpated and there should be an indentation in front of the pelvic wings (waist line).
Controlled exercise is indicated to prevent or relieve the inflammatory process that leads to the pain associated with arthritis. The amount and difficulty of the activity is determined on a trial and error basis. Exercise should start with short leash walks and be gradually increased until the dog reaches the desired level of activity. If clinical signs start to reappear, the amount of exercise is scaled back to a level that will not cause clinical signs. Overall, exercise should fit to an individual dog's maximum intensity level with the goal to maintain muscle tone and cardiovascular function without causing pain, stiffness, and inflammation to the joint. The right amount of exercise helps to maintain muscle tone and strength and stabilizes the unstable dysplastic joint. Exercise also improves joint range of motion which in turn, keeps the dog more comfortable. Swimming, because it is a non-weight bearing exercise, can be a very useful means of maintaining muscle tone and range of motion without placing concussive forces on the joint.
Keep the dog in a warm environment which tends to help control the pain of arthritis from hip dysplasia. As in people, arthritic pain in dogs tends to be worse in the damp and cold of winter. Providing a well-padded and warm bed that will help alleviate some of the pain associated with osteoarthritis. An egg-crate foam bed for dogs is commercially available. Applying superficial heat in the form of heating pads may also relieve pain. Care must be taken not to burn the skin especially with an electric heating pad. Heat works best for chronically inflamed joints from arthritis while cold works better to treat acute (sudden) types of joint injury.
Numerous drugs are available to control the signs of osteoarthritis secondary to CHD. The use of nonsteroidal anti-inflammatory pain relievers such as Buffered aspirin, EtoGesic (Fort Dodge) or Rimadyl (Pfizer) can be used during bouts of lameness. These drugs inhibit prostaglandin release which decreases the inflammatory process and therefore, less pain is produced. These medications can also be given an hour or so before known periods of exercise to decrease inflammation. Side effects may be seen in some dogs which include vomiting, diarrhea, and inappetence.
Various alternative drug therapies known as disease-modifying osteoarthritis agents can be used. According to the manufacturers, these drugs work by providing the raw materials to enhance the synthesis of glycosaminoglycan and hyaluronate that cannot be adequately produced in the diseased arthritic joint. These are the molecules that form proteoglycan, which is an important constituent of the hyaline cartilage that lines the joint. These drugs may also enhance the synthesis of other macromolecules by cartilage cells that inhibit degradative enzymes produced within the arthritic joint. Controlled studies have been reported about the positive effects in people for osteoarthritis. No controlled studies, to date, have been reported on the clinical response when treating arthritis in dogs but clinically most dogs seem to respond.
Oral disease-modifying osteoarthritis agents known as nutraceuticals are now on the market and are available over-the-counter for people. Various veterinary products can also be obtained, examples include; Cosequin (Nutramax Laboratories), SynoviCre (DVM Laboratories), Glycoflex (Vetri-Science Laboratories), Arthramine (Vesta Laboratories), and MaxFlex Pet (Farnam Inc.). These drugs take approximately one month to reach therapeutic levels in the blood stream. Minimal to no side effects have been reported with their use.
Injectable disease-modifying osteoarthritis agents are another alternative therapeutic choice. Examples of these products include Hyaluronic acid and Polysulfated Glycosaminoglycans (Adequan). Adequan is also now available in oral form. These drugs can be injected into the joint, vein or muscle and have been shown to be a useful adjunctive treatment for osteoarthritis in dogs. Since these drugs are injected, more rapid therapeutic levels are obtained. They may be initially used with the oral nutraceuticals for a series of injections for one month since the oral agents take approximately one month to reach therapeutic levels. The literature indicates that the earlier these drugs are administered, the more likely it will decrease inflammation and protect against cartilage degradation in osteoarthritis.
The use of these drugs should be tailored for the individual dogs improvement noted. If side-effects occur like GI upset, the medication should be given with food or discontinued altogether. If there is persistence of obvious lameness/pain after approximately 6 months using one medication, change the therapy to a different medication from the above choices.
For surgical intervention
In younger dogs usually less than 10 months old with only subluxation caused by dysplasia, a triple pelvic osteotomy can be performed to re-establish joint stability and encourage normal joint development and minimize abnormal biomechanical forces on the joint before osteoarthritis occurs. This procedure is not indicated if osteoarthitis is already present. Recovery time is about 6 weeks and a good success rate has been reported with return of normal hip function.
For older dogs (over 10 months) over 35 pounds that already have established osteoarthritis and can no longer be medically managed, a total hip replacement is the treatment of choice for re-establishing normal, pain-free limb function and joint mechanics. A high degree of success has been reported with this surgery and like the TPO, post-op recovery is about 4-6 weeks. The main disadvantage to this surgery is the high cost.
An alternative surgery which is more of a salvage procedure when there is significant osteoarthritis and a total hip is cost prohibitive is a femoral head and neck excision. This eliminates hip pain by removing the femoral head and neck and initiating the development of a fibrous false joint that permits ambulation. The procedure can be performed in all dogs of all sizes, but results where good return of mechanical joint function occurs are usually better in smaller dogs less than 20 kg. Keep in mind for heavier dogs there is more extensive post-operative rehabilitation (up to 4 months) to form a pain-free false joint. Rehabilitation would include lots of work aiding the dog in walking around, getting up and down, and physical therapy to increase muscle strength and flexibility. Prior to initiating any therapy, the attending veterinarian should be consulted with a complete medical history and physical examination. For hip surgeries, to find the name of a board-certified veterinary surgeon in your area (Diplomate ACVS), call 301-718-6504. Only those veterinarians who have earned Diplomate status in the American College of Veterinary Surgery are true specialists in veterinary surgery.
