The OFA's Hip Radiograph Procedures
General Overview
Radiographs submitted to the OFA should follow the American Veterinary Medical Association recommendations 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.
- Craniolateral
acetabular rim
- Cranial
acetabular margin
- Femoral
head (hip ball)
- Fovea
capitus (normal flattened area on hip ball)
- Acetabular
notch
- Caudal
acetabular rim
- Dorsal
acetabular margin
- Junction
of femoral head and neck
- 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:
- Excellent
- Good
- Fair
- Borderline
- Mild
- Moderate
- 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.
