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OFA Hip Dysplasia Hip Dysplasia

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									                                    OFA Hip Dysplasia

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.




                                   Preliminary Testing

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).

*Corley, EA, et al. Reliability of Early Radiographic Evaluation for Canine Hip
Dysplasia Obtained from the Standard Ventrodorsal Radiographic Projection. JAVMA.
Vol 211, No. 9, November 1997.


                               Hip Grades

The phenotypic evaluation of hips done by the Orthopedic Foundation for Animals
falls into seven different categories. Those categories are normal (Excellent, Good,
Fair), Borderline, and dysplastic (Mild, Moderate, Severe). Once each of the
radiologists classifies the hip into one of the 7 phenotypes above, the final hip grade
is decided by a consensus of the 3 independent outside evaluations. Examples would
be:

   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

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
(tattoo, microchip) 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 not in the
public domain.


Excellent


Excellent (Figure 1): this classification is assigned for superior conformation in
comparison to other animals of the same age and breed. There is a deep seated ball
(femoral head) which fits tightly into a well-formed socket (acetabulum) with
minimal joint space. There is almost complete coverage of the socket over the ball.




Good


Good (Figure 2): slightly less than superior but a well-formed congruent hip joint is
visualized. The ball fits well into the socket and good coverage is present.




Fair
Fair (Figure 3): Assigned where minor irregularities in the hip joint exist. The hip
joint is wider than a good hip phenotype. This is due to the ball slightly slipping out
of the socket causing a minor degree of joint incongruency. There may also be slight
inward deviation of the weight-bearing surface of the socket (dorsal acetabular rim)
causing the socket to appear slightly shallow (Figure 4). This can be a normal finding
in some breeds however, such as the Chinese Shar Pei, Chow Chow, and Poodle.




Borderline


Borderline: there is no clear cut consensus between the radiologists to place the hip
into a given category of normal or dysplastic. There is usually more incongruency
present than what occurs in the minor amount found in a fair but there are no
arthritic changes present that definitively diagnose the hip joint being dysplastic.
There also may be a bony projection present on any of the areas of the hip anatomy
illustrated above that can not accurately be assessed as being an abnormal arthritic
change or as a normal anatomic variant for that individual dog. To increase the
accuracy of a correct diagnosis, it is recommended to repeat the radiographs at a
later date (usually 6 months). This allows the radiologist to compare the initial film
with the most recent film over a given time period and assess for progressive
arthritic changes that would be expected if the dog was truly dysplastic. Most dogs
with this grade (over 50%) show no change in hip conformation over time and
receive a normal hip rating; usually a fair hip phenotype.


Mild


Mild Canine Hip Dysplasia (Figure 5): there is significant subluxation present where
the ball is partially out of the socket causing an incongruent increased joint space.
The socket is usually shallow only partially covering the ball. There are usually no
arthritic changes present with this classification and if the dog is young (24 to 30
months of age), there is an option to resubmit an radiograph when the dog is older
so it can be reevaluated a second time. Most dogs will remain dysplastic showing
progression of the disease with early arthritic changes. Since HD is a chronic,
progressive disease, the older the dog, the more accurate the diagnosis of HD (or
lack of HD).




Moderate


Moderate Canine Hip Dysplasia: there is significant subluxation present where the
ball is barely seated into a shallow socket causing joint incongruency. There are
secondary arthritic bone changes usually along the femoral neck and head (termed
remodeling), acetabular rim changes (termed osteophytes or bone spurs) and
various degrees of trabecular bone pattern changes called sclerosis. Once arthritis is
reported, there is only continued progression of arthritis over time.


Severe


Severe HD (Figure 6): assigned where radiographic evidence of marked dysplasia
exists. There is significant subluxation present where the ball is partly or completely
out of a shallow socket. Like moderate HD, there are also large amounts of
secondary arthritic bone changes along the femoral neck and head, acetabular rim
changes and large amounts of abnormal bone pattern changes.




 Hip Dysplasia Radiograph Procedures

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


General Information

Radiographs submitted to the OFA must follow the American Veterinary Medical
Association guidelines for positioning. This view is accepted world wide for detection
and assessment of hip joint irregularities and secondary arthritic hip joint changes.
To obtain this view, the animal must be placed on its back in dorsal recumbency with
the rear limbs extended and parallel to each other. The knees (stifles) are rotated
internally and the pelvis is symmetric. Chemical restraint (anesthesia) to the point of
relaxation is recommended. For elbows, the animal is placed on its side and the
respective elbow is placed in an extreme flexed position.

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

Proper collimation and protection of attendants is the responsibility of the
veterinarian. Gonadal shielding is recommended for male dogs.


Mailing Recommendations

The radiograph, application and fees should be enclosed in a mailing envelope. These
may be paper clipped together. Use the mail service of your choice. Obtain large
envelopes from office supply store, veterinary hospital or other radiology
department. The envelope should be sealed with tape. Light cardboard may be
included to stiffen the package, but is not required. Avoid using boxes, tubes,
padded envelopes, stapling check and application, bending/folding radiographs, or
taping application or check to envelope.


OFA's Handling Procedures

When a radiograph arrives at the OFA, the information on the radiograph is checked
against information on the application. The age of the dog is calculated, and the
submitted fee is recorded. The board-certified veterinary radiologist on staff at the
OFA screens the radiographs for diagnostic quality. If it is not suitable for diagnostic
        quality (poor positioning, too light, too dark or image blurring from motion),
        it is returned to the referring veterinarian with a written request that it be
        repeated. An application number is assigned.

        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

When results of 1.8 million radiographic evaluations by 45 radiologists were
analyzed, it was found that all three radiologists agreed as to whether the dog should
be classified as having a normal phenotype, borderline phenotype, or HD 94.9% of
the time. In addition, 73.5% of the time, all three radiologists agreed on the same
hip phenotype (excellent, fair, good, borderline, mild, moderate or severe). Twenty-
one percent of the time, two radiologists agreed on the same hip grade and the third
radiologist was within one hip grade of the other two. Two radiologists agreed on the
same hip grade and the third radiologist was within two hip grades of the other two
5.4% of the time. This percentage of agreement is high considering the subjective
nature of the evaluation.


Other Radiographic Findings

In addition to assessing the dog's hip conformation, the veterinary radiologist reports
other radiographic findings that could have familial, inherited causes such as
transitional vertebrae or spondylosis.

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.

								
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