Contributors: Patsy Whelehan
Species: Feline | Classification: Techniques
- Conditions affecting the scapula are comparatively rare, but when radiography is necessary, it is not an easy area to show effectively.
- If general anesthesia is not used, then heavy sedation with analgesia is needed, in respect of the craniocaudal projection.
- The film must include the whole bone, must be correctly exposed and developed and 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.
- Fracture Fracture: overview .
- Dependent upon the method of chemical restraint (GA or sedation).
- 10 to 15 minutes, or longer, dependent upon skill of radiographer.
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?
Choosing the right projections
- Two projections are necessary for a full assessment, whether for neoplastic disease or fracture.
Lateral shoulder projection
- For demonstrating the glenoid cavity of the scapula this is the position of choice in conjunction with the craniocaudal.
Lateral projection, through lungs
- Shows part of the body of the scapula.
- This projection is simple to position and brings the bone into a flat orientation parallel to the film.
- It has the disadvantage that a number of structures, most problematically some of the vertebrae, overly the scapula making interpretation difficult.
- This successfully demonstrates the neck and body of the scapula without the problem of overlying structures.
- While the obliquity causes some foreshortening this view is likely to be of more overall use than the "through lung" lateral.
- It is also easy to position and can be reversed if the patient is too painful to lie on the affected side.
- Radiographer, or Technician carrying out radiography.
- X-ray machine.
- Cassettes with high definition screens.
- Processing facilities.
- Immobilization and positioning aids: sandbags, foam wedges, tying tapes.
- Protective clothing (lead-rubber apron).
- High output X-ray machine.
- Rare earth screens.
- Automatic processing facilities.
- X-ray film.
- Pharmaceuticals for chemical restraint.
- One to two competent people.
- Foam wedges.
- Tying tapes.
- Positioning trough.
Step 1 - Lateral projection, through lungs
- Place the patient in lateral recumbency on the side to be examined and immobilize.
- Distract the affected forelimb caudally and the unaffected (uppermost) forelimb craniallyand secure.
- Try to palpate the scapula under examination, or use whatever relevant landmarks are accessible, and center about mid scapular spine .
- Collimate to include the whole scapula.
There should not be any need to arrest inspiration for this radiograph. The bone will be immobilized by the animal's weight upon it and blurring of the lung fields may help to increase the clarity of the scapula.
Step 2 - Craniocaudal projection
- Place the patient in dorsal recumbency in a trough and immobilize.
- Rotate the thorax away from the affected side.
- Using a tie, extend the affected limb as far cranially as possible and secure .
- Adjust position of thorax and limb to ensure the joint is in the true craniocaudal position.
- Center the vertical beam through the middle of the scapula by palpation.
- Collimate to include the whole scapula with the shoulder joint .
Step 3 - Craniomedial-caudolateral oblique
- A grid is not required.
- The patient is positioned in lateral recumbency on the side under examination.
- The cassette is placed under the scapula, protruding dorsally.
- The thorax is rotated to bring the sternum close to the table top.
- The median sagittal plane should make an angle of approximately 20 degrees to the table top.
- The limb on the affected side is flexed, pushed dorsally and secured. The contralateral limb is drawn ventrally and secured .
- Center with a vertical beam half way along the scapular spine.
- The whole scapula is projected dorsal to the thoracic spine .
Reasons for Treatment Failure
- If the lateral projection fails to demonstrate enough of the scapula, opt for the oblique.
- The oblique projection may result in the dorsal edge of the scapula being over exposed due to the lack of overlying soft tissues. To rectify this try a higher kV technique to decrease image contrast.
- The greatest problem in the craniocaudal projection is likely to be rotation. Careful positioning is required. Remember to turn the thorax away from the affected side and palpate the bone thoroughly. Ensure that immobilization is effective.
- Inadequate sedation.
- Poor processing.
- Equipment failure.