Contributors: Justin Goggin, Patsy Whelehan
Species: Canine | Classification: Techniques
- Attention to detail in radiographing the pelvis is important, as high standards of positioning are vital for accurate radiological assessment Radiographic positioning video: lateral pelvis.
- A secondary radiation grid should be used for larger breed dogs.
- A good supply of the appropriate positioning aids is needed.
- It is particularly important that the patient is highly compliant, GA or heavy sedation with analgesia is required.
- The image should include the whole pelvis, the stifle joints, and the soft tissues surrounding the femora, as any muscle atrophy should be noted.
- The film should be checked for correct positioning, exposure and processing and should be free from movement blur and artifact.
- The anatomical marker must be clearly visible, along with the patient's identification, the date, and the name of the hospital or practice.
- When radiographing the pelvis for an OFA hip dysplasia evaluation, the Kennel Club number, patients AKC or registered name,owners name, hospital or veterinarians name, anatomical marker and date must be exposed on to the film.
- Lead letters and numbers, an ID camera or X-Rite tape can be used for this, but the latter sometimes does not appear very clearly, particularly where high exposure factors are used.
- The Penn hip distraction radiograph technique is reported to provide a selection of breeding stock based on a distraction index. It is reported to be the best method of reducing the numbers of dysplastic dogs in a given breeding population.
- Veterinarians must participate in a Penn hip training course and obtain a Penn hip distraction device to perform and submit films for Penn hip evaluation.
- Fractures of the pelvis .
- Fractures or tumors of the proximal femur.
- Aseptic necrosis of the femoral head (Legg Perthes disease) Hip: aseptic femoral head/neck necrosis .
- Dislocation of the coxofemoral joint Hip: luxation.
- Hip dysplasia diagnosis Hip: dysplasia.
- Post-operative assessment of hip replacement surgery or triple pelvic osteotomy.
- Neoplastic disease .
- Osteomyelitis Osteomyelitis.
- Lumbosacral degenerative disease and discospondylitis Diskospondylitis.
- Equipment readily available.
- Patient +/- human exposure to radiation.
- Dependent upon method of chemical restraint (GA or sedation).
- 10 - 15 min or longer, dependent upon skill of radiographer and availability of a rapid automatic X-ray film processor.
The patient should be left in position while the film is processed, if possible, so that any inaccuracies in the projection can be corrected from the original position.
Criteria for choosing test
Is the examination appropriate?
- Can you make the diagnosis without it?
- Can it tell you what you need to know?
- Will your management be affected by the radiological findings?
- The standard and most useful projection for evaluation of degenerative changes associated with hip dysplasia.
- Enables detection of most fractures and assessment of the coxofemoral joints.
- Neccessary for complete radiographic evaluation of region.
- Shows direction of displacement in hip dislocation.
- Necessary for assessment of fracture displacement.
- Most valuable view to assess the lumbosacral junction.
- Important for assessing fractures or neoplasia involving the femoral head and neck.
- Necessary for complete evaluation for abnormalities associated with the femoral component of a hip replacement prosthesis.
- Radiographer, or veterinary nurse/technician to carry out radiography.
- X-ray machine.
- Some type of film ID system.
- Cassettes with high definition to fast screens, depending on the size of the dog.
- Processing facilities (PennHIP certification requires the practice to own an automatic processor).
- Immobilization and positioning aids: sandbags, foam wedges, tying tapes, medical adhesive tape.
- Protective clothing (lead-rubber aprons, gloves, thyroid shields (US only)).
- Availability of chemical restraint (injectable).
- High output X-ray machine.
- Rare earth screens.
- Film ID camera.
- Automatic processing facilities.
- Grid (for patients with thickness >10 cm).
- Hooks on the end of the X-ray table for attaching tapes used to extend legs.
- Gas anesthesia.
- X-ray film.
- Film ID card/ID tape.
- Pharmaceuticals for chemical restraint.
- Fast patient for 12 hours prior to anesthesia to prevent reflux esophagitis.
- Usually two competent people.
- Foam wedges.
- Positioning trough.
- +/- chemical restraint.
- Adhesive tape, rope or roll gauze
Step 1 - Ventrodorsal
- Place the patient in dorsal recumbency, thorax in a positioning trough.
- Immobilize the forelimbs and trunk with cloth adhesive tape or rope.
- Foam wedges or small sandbags between the thorax and the sides of the trough may be helpful to prevent rotation.
When standing at the dog's head during this procedure be very careful not to be bitten, as it is a particularly vulnerable situation for personnel.
Use a muzzle if in doubt.
- Make sure that the thorax is not rotated to the side, as this would make it more difficult to keep the pelvis straight.
- Place a tie around each hindlimb above the hocks.
- Draw the hindlimbs caudally to maximum extension of the hips and stifles and secure the ties, to the table if possible, otherwise to sandbags. Placing a 3-4 inch high foam block below the hocks may help stabilize the patient.
- Rotate the hindlimbs medially until the femora are parallel to each other and the stifles are in a true craniocaudal position .
- Secure the femora in this position by tying a rope or gauze around them, or, more conveniently, by using white cloth adhesive tape wrapped round a number of times . If sticky tape is used it should be easy to tear for removal.
- Stand at the caudal end of the table and place the hands under the pelvis.
- Palpate the wings of each ilium and rotate the pelvis until these are equidistant from the film.
A lightweight long sandbag placed across the hocks (supported from the underneath if necessary), will further help to prevent rotation.
- Collimate to include from the wings of ilium to just below the stifle joints .
It is not necessary to include the stifles for the BVA HD scheme in the UK.
- Include the femoral musculature in the beam.
If possible, prevent any movement of the patient until the radiograph has been processed and checked.
Step 2 - Lateral pelvis
- Place the patient in lateral recumbency on the X-ray table and immobilize with sandbags.
- It is not critical on which side the patient lies but it is wise to follow the principle of placing the side of interest nearer the film unless this would result in undue pain to the patient.
- To achieve a true lateral position of the pelvis palpate the wings of the ilium and ensure that these are lying one above the other.
- Use foam wedges between the femora to maintain the true lateral position.
- In some patients it may be necessary to pad the pelvis dorsally to achieve the true lateral position.
- Position the down femur cranial to the non-dependent femur.
- Center with a vertical beam over the femoral head.
- Collimate to include the entire pelvis.
Step 3 - Lateral single hip
- This position is most easily achieved from the ventrodorsal position with the patient's thorax placed in a trough and tilted towards the side under examination.
- Use a combination of ties and sandbags to abduct the unaffected limb and stabilize the trunk and forelimbs.
- Flex the affected hip and stifle and bring this femur parallel to the film.
- Center with a vertical beam through the hip joint .
- Collimate to include the whole of the joint and the entire femur if a femur lesion is suspected, or the proximal third of the femur if an acetabular lesion is suspected .
Step 1 - Assessing film quality and correcting rotation
- In the case of a ventrodorsal radiograph showing a rotated projection it is important to know how to recognize and correct this.
- Compare the size of the obturator foramina.
- If one foramen appears SMALLER, this side of the pelvis is rotated TOWARDS the film.
- Alternatively, or additionally, compare the apparent width of the wings of ilium.
- If one side appears WIDER this side is rotated TOWARDS the film.
When correcting this on the patient, be reasonably positive - move the bones, not just the soft tissues.
- The femora should be parallel to each other.
- The entire pelvis and stifles should be visible on the VD view.
- The patellas should be superimposed on midline over the trochlear ridges of the femora.
Reasons for Treatment Failure
- Inadequate sedation.
- Incomplete studies (single view only) lead to inaccurate diagnosis.
- Poor processing.
- Equipment failure.
- Poor radiographic technique: inaccurate positioning, inappropriate collimation, incorrect exposure factors, failure to label film.
- The most common problem is rotation of the pelvis when carrying out the ventrodorsal view.
- To avoid rotation it is necessary to palpate the pelvis as well as look at the patient.
- Using only a visual check can be inaccurate due to asymmetry of the soft tissues or optical illusions caused by coat markings.
- Remember to consider the whole animal when positioning.
If the thorax is rotated then it will be very difficult to obtain a straight pelvis.
- Recent references from PubMed and VetMedResource.
- Adams W M, Dueland R T, Meinen J et al (1998) Early detection of canine hip dysplasia: comparison of two palpation and five radiographic methods. JAAHA 34 (4), 339-347 PubMed.
- Slocum B & Devine T M (1990) Dorsal acetabular rim radiology view for evaluation of the canine hip. JAAHA 26 (3), 289-296 CAB Direct.