Contributors: Patsy Whelehan
Species: Feline | Classification: Techniques
Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading
- Accurate centering is essential when radiographing any joint.
- High definition film-screen combinations are required.
- A grid is not necessary.
- kV should not exceed about 50.
- Close collimation is essential.
- If general anesthesia is not used, then heavy sedation with analgesia is needed.
- The film must include the whole joint, with soft tissues, 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.
- An important diagnostic aid in determining the cause of a lameness arising from the shoulder.
- Bony injury: fracture or dislocation Shoulder: luxation - traumatic.
- Bony neoplasia or soft tissue neoplasia invading bone Synovial sarcoma.
- Investigation of soft tissue injury.
- Joint effusion, swelling .
- Poor positioning can make subtle pathology impossible to detect.
- The presence of severe pain can make the procedure difficult in a conscious patient.
- 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
Lateral: standard projection
- Shows glenoid cavity and head of humerus.
- Demonstrates joint space.
- Shows soft tissue swelling and joint effusions.
- Can show calcification in tendons.
Craniocaudal: second standard projection, or supplementary
- Essential second view in cases of known or suspected fracture.
- Usually necessary in cases of dislocation.
- 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 aprons).
- High output X-ray machine.
- Rare earth high definition 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
- Place the patient in lateral recumbency on the side to be examined and immobilize.
- Use a sandbag to hold the contralateral limb out of the field caudally and dorsally .
- Use a tie to distract the affected limb well cranially, and secure.
- With foam wedges, pad under the elbow to ensure the humerus is parallel to the film.
Locate by palpation of the lateral aspect of the shoulder joint space.
- Center with a vertical beam directly through the joint space .
- Collimate to include the entire glenoid cavity, the soft tissues of the joint, and the proximal third of the humerus .
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 joint space by palpation of the lateral aspect.
- Collimate to include the soft tissues of the joint and the proximal third of the humerus .
Step 3 - Cranioproximal-craniodistal (bicipital groove) projection
- Place the patient in sternal recumbency .
- Flex the shoulder and the elbow.
- Abduct the radius slightly so that it does not lie beneath the shoulder.
- Palpate the groove on the cranial aspect of the head of humerus and direct the beam tangentially through it.
- Collimate closely.
Reasons for Treatment Failure
- Inadequate sedation.
- Poor technique: inaccurate positioning or centering, wrong exposure factors.
- Poor processing.
- Equipment failure.
- Recent references from PubMed and VetMedResource.
- Allan G S (2000) Radiographic features of feline joint disease. Vet Clin North Am Small Anim Pract 30 (2), 281-302 PubMed.