General Hip Dysplasia Information

The Dysplastic Joint

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 articular cartilage (the type of cartilage lining the joint) damage due to the inherited bad biomechanics of an abnormally developed hip joint. Traumatic articular fracture through the joint surface is 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 important constituent molecules that form 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. Full thickness loss of cartilage allows the synovial fluid to contact nerve endings in the subchondral bone, resulting in pain. 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 no rhyme or reason 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 that are severely lame.

Hip Dysplasia Radiograph Procedures

General Information
Radiation Safety
Mailing Recommendations
OFA's Handling procedures
Accuracy of Data
Other Radiographic Findings

General Information

The radiograph film must be permanently identified with the animal's registration number or name, date the radiograph was taken, and the veterinarian's name or hospital name. If this required information is illegible or missing, the OFA cannot accept the film for registration purposes. The owner should complete and sign the OFA application. It is important to record on the OFA application the animal's tattoo or microchip number in order for the OFA to submit results to the AKC. Sire and dam information should also be present.

Radiography of pregnant or estrus females should be avoided due to possible increased joint laxity (subluxation) from hormonal variations. OFA recommends radiographs be taken one month after weaning pups and one month before or after a heat cycle. Physical inactivity because of illness, weather, or the owner's management practices may also result in some degree of joint laxity. The OFA recommends evaluation when the dog is in good physical condition.

Chemical restraint (anesthesia) is not required by OFA but chemical restraint to the point of muscle relaxation is recommended. With chemical restraint optimum patient positioning is easier with minimal repeat radiographs (less radiation exposure) and a truer representation of the hip status is obtained.

For large and giant breed dogs, 14" x 17" film size is recommended. Small film sizes can be used for smaller breeds if the area between the sacrum and the stifles can be included.

If a copy is necessary ask your veterinarian to insert 2 films in the cassette prior to making the exposure. This will require about a 15% increase in the kVp to make an exact duplicate of the radiograph sent to OFA. Films may be returned if a $5.00 fee and request for return are both included at time of submission.

Good contrast is desirable (high mAs, low kVp). Grid techniques are recommended for all large dogs.

Radiation Safety

Mailing Recommendations

OFA's Handling Procedures

 Radiographs of animals 24 months of age or older are independently evaluated by three randomly selected, board-certified veterinary radiologists from a pool of 20 to 25 consulting radiologists throughout the USA in private practice and academia. Each radiologist evaluates the animal's hip status considering the breed, sex, and age. There are approximately 9 different anatomic areas of the hip that are evaluated (Figure 1).

1. Craniolateral acetabular rim
2. Cranial acetabular margin
3. Femoral head (hip ball)
4. Fovea capitus (normal flattened area on hip ball)
5. Acetabular notch
6. Caudal acetabular rim
7. Dorsal acetabular margin
8. Junction of femoral head and neck
9. Trochanteric fossa

The radiologist is concerned with deviations in these structures from the breed normal. Congruency and confluence of the hip joint (degree of fit) are also considered which dictate the conformation differences within normal when there is an absence of radiographic findings consistent with HD. The radiologist will grade the hips with one of seven different physical (phenotypic) hip conformations: normal which includes excellent, good, or fair classifications, borderline or dysplastic which includes mild, moderate, or severe classifications.

Seven classifications are needed in order to establish heritability information (indexes) for a given breed of dog. Definition of these phenotypic classifications are as follows:

1. Excellent
2. Good
3. Fair
4. Borderline
5. Mild
6. Moderate
7. Severe

(See What Do Hip Grades Mean for more detail on the classifications)

The hip grades of excellent, good and fair are within normal limits and are given OFA numbers. This information is accepted by AKC on dogs with permanent identification and is in the public domain. Radiographs of borderline, mild, moderate and severely dysplastic hip grades are reviewed by the OFA radiologist and a radiographic report is generated documenting the abnormal radiographic findings. Unless the owner has chosen the open database, dysplastic hip grades are closed to public information.

Accuracy of Data

Other Radiographic Findings

Transitional vertebrae are a congenital malformation of the spine that occur at the junctions of major divisions of the spine (usually between the thoracic and lumbar vertebral junction and the lumbar and sacral vertebral junction). Transitional vertebrae take on anatomic characteristics of both divisions of the spine it occurs between. The most common type of transitional vertebrae in dogs is in the lumbo-sacral area where the last lumbar vertebral body takes on anatomic characteristics of the sacrum. Transitional vertebrae are usually not associated with clinical signs and the dog can be used in a breeding program. The OFA recommends breeding the dog to another dog that does not have transitional vertebrae.

Spondylosis is another incidental radiographic finding where smooth new bone production is visualized between vertebral bodies at the intervertebral disc spaces. The new bone production can vary in extent from formation of small bone spurs to complete bridging of adjacent vertebral bodies. Spondylosis may occur secondary to spinal instability but often it is of unknown cause and clinically insignificant. A familial basis for its development has been reported. Like transitional vertebrae, dogs with spondylosis can be used in a breeding program.

1. Two radiologists reported excellent, one good—the final grade would be excellent
2. One radiologist reported excellent, one good, one fair—the final grade would be good
3. One radiologist reported fair, two radiologists reported mild—the final grade would be mild

• Breed normals to normals
• Breed normals with normal ancestry
• Breed normals from litters (brothers/sisters) with a low incidence of HD
• Select a sire that produces a low incidence of HD

Preliminary Evaluations

for animals under 24 months

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OFA policy on Releasing Preliminary Evaluations to the Public Domain.

Frequently, breeders want early knowledge of the hip status on puppies in a given litter. Preliminary hip evaluations may be as valuable to the owner or breeder as the final OFA evaluation. This allows early selection of dogs for use as show/performance/breeding prospects and dogs best suited for pet homes.

The OFA accepts preliminary consultation radiographs on puppies as young as 4 months of age for evaluation of hip conformation. If the dog is found to be dysplastic at an early age, the economic loss from the cost of training, handling, showing and so forth can be minimized and the emotional loss reduced. These preliminary radiographs are read by the OFA veterinary radiologists and are not sent to outside radiologists. The same hip grades are given to preliminary cases.

A recent publication* compared the reliability of the preliminary evaluation hip grade phenotype with the 2 year old evaluation in dogs and there was 100% reliability for a preliminary grade of excellent being normal at 2 years of age (excellent, good, or fair). There was 97.9% reliability for a preliminary grade of good being normal at 2 years of age, and 76.9% reliability for a preliminary grade of fair being normal at 2 years of age. Reliability of preliminary evaluations increased as age at the time of preliminary evaluation increased, regardless of whether dogs received a preliminary evaluation of normal hip conformation or HD. For normal hip conformations, the reliability was 89.6% at 3-6 months, 93.8% at 7-12 months, and 95.2% at 13-18 months. These results suggest that preliminary evaluations of hip joint status in dogs are generally reliable. However, dogs that receive a preliminary evaluation of fair or mild hip joint conformation should be reevaluated at an older age (24 months).

Hip Dysplasia Treatment Options

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General Guidelines
Drug Treatments
Surgical Interventions
Summary

General Guidelines

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. Warmth 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 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.

Drug Treatments

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. 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 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 and any 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.

Surgical Interventions

For older dogs (over 10 months) that already have established osteoarthritis and can no longer be medically managed, a total hip replacement is the treatment of choice for reestablishing 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 false joint is less stable with a reduced range of motion than the normal joint which in turn, causes an abnormal gait. Nevertheless, pain relief with adequate function can be achieved. The procedure can be performed in all dogs of all sizes, but there are usually better long-term success rates in smaller dogs less than 20 kg (about 44 pounds). Preoperative muscle mass and early postoperative physical therapy are two important factors in determining a successful outcome. This surgery is usually not as successful if there is severe disuse muscle wasting (atrophy) present and/or the animal is obese.

Heavier dogs usually require more extensive postoperative rehabilitation to help promote an ambulatory pain-free false joint. Rehabilitation is aimed at preserving and promoting the leg's muscle mass, strength and range of motion through early (3-5 days) postoperative weight bearing ambulation and passive range-of-motion exercises. Early ambulation can be achieved by assisting the dog in getting up and walking. A towel can be placed under the abdomen to make assistance easier to perform in heavy dogs. Leash walks and/or swimming beginning the day of discharge from the hospital should be performed until near normal use of the leg returns. Passive range of motion physical therapy is also necessary to increase muscle strength and flexibility. Dogs that are obese, inactive or have substantial muscle atrophy and have poor owner compliance with physical therapy recommendations are poor candidates for this surgery.

Summary

Prior to initiating any therapy, the attending veterinarian should be consulted with a complete medical history and physical examination. To locate a surgeon in your area, the following web site is available: www.acvs.org. Only those veterinarians who have earned Diplomate status in the American College of Veterinary Surgery are listed.