Contributors: Justin Goggin, Patsy Whelehan

 Species: Canine   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading

Introduction

  • 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, especially for the craniocaudal projection.
  • A grid is necessary for patients with thickness >10 cm.
  • The film must include the whole bone, must be correctly exposed and developed, and free from movement blur and artefact.
  • The anatomical marker must be clearly visible, along with the patient's identification, the date, and the name of the hospital or practice.

Uses

Advantages

  • Non-invasive.

Disadvantages

  • Radiation exposure to patient/personnel.

Time Required

Preparation

  • Dependent upon the method of chemical restraint, (GA or sedation).

Procedure

  • 10-15 min or longer, dependent upon skill of radiographer.

Decision Taking

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
  • At least two projections are necessary for a full assessment.
Lateral shoulder projection
  • For demonstrating theglenoid cavityof the scapula, this is the position of choice in conjunction with the caudocranial.
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), overlie the scapula making interpretation difficult.
Craniomedial-caudolateral oblique
  • 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 it is too painful for the patient to lie on the affected side.
Caudocranial view
  • Provides undistorted view.
  • Easy to obtain.
Distoproximal view
  • Provides a tangential view of scapular spine and body.
  • Useful to characterize and detect subtle lesions such as green stick fractures.

Requirements

Personnel

Other involvement

  • Radiographer or veterinary nurse/technician carrying out radiography.

Materials Required

Minimum equipment

  • X-ray machine.
  • Cassettes with high definition screens, and fast screens if performing the lateral projection in a larger dog.
  • Processing facilities.
  • Immobilization and positioning aids: sandbags, foam wedges, tying tapes.
  • Protective clothing (lead-rubber apron, etc).
  • Film ID system.

Ideal equipment

  • High output X-ray machine.
  • Rare Earth screens.
  • Automatic processing facilities.

Minimum consumables

  • X-ray film.
  • Pharmaceuticals for chemical restraint.
  • Film ID card or tape.

Preparation

Restraint

  • 1-2 competent people.
  • Sandbags.
  • Foam wedges.
  • Tying tapes.
  • Positioning trough.

Procedure

Core Procedure

 

Step 1 - Lateral projection through lungs

 
  • A grid is required in larger dogs (>10 cm thickness).
  • Place the patient in lateral recumbency on the side to be examined and immobilize.
  • Distract theaffectedforelimbcaudally, and theunaffected(uppermost) forelimbcraniallyand 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 - Caudocranial 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 Radiographic positioning scapula - caudocranial projection.
  • Adjust position of thorax and limb to ensure the joint is in the true caudocranial 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° to the table top.
  • The limb on the affected side is flexed, pushed dorsally and secured. The contralateral limb is drawn ventrally and secured Radiographic positioning scapula - CM  CL oblique.
  • Center with a vertical beam half way along the scapular spine.
  • The whole scapula is projected dorsal to the thoracic spine.

Exit

 

Step 1 - Distoproximal view

 
  • Grid required if tissue thickness >10 cm.
  • Patient positioned in dorsal recumbency.
  • Cassette is placed under the scapula of interest.
  • The affected limb is drawn as far caudally as possible and secured.
  • Center the beam and collimate to include the humeral head and scapula (based on palpation).

Aftercare

Outcomes

Reasons for Treatment Failure

technique
  • 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 caudocranial 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.
Other
  • Incomplete studies (one view only), can lead to misdiagnosis.
  • Inadequate sedation.
  • Poor processing.
  • Equipment failure.
  • Poor radiographic technique - inaccurate positioning or collimation, incorrect exposure factors, failure to label film.

Further Reading

Publications

Refereed papers