Contributors: Patsy Whelehan

 Species: Feline   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading

Introduction

  • A high definition film-screen combination is required.
  • A grid is not required.
  • kV should not exceed about 50.
  • Both joints should always be included.
  • Soft tissues should be included.
  • General anesthesia or heavy sedation is required.
  • The film should 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.

Uses

Advantages

  • Non-invasive.
  • Straightforward.

Time Required

Preparation

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

Procedure

  • 10 to 15 minutes, 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

Lateral
  • Standard projection.
Caudocranial
  • Standard projection.
  • However, not necessary for panosteitis: lateral only is sufficient.
Craniocaudal (with limb positioned beside thorax)
  • Alternative to caudocranial.
  • Enables distal humerus to lie flatter against film, thus minimizing distortion without the need for tube angulation.

Requirements

Personnel

Other involvement

  • Radiographer, or Technician carrying out radiography.

Materials Required

Minimum equipment

  • X-ray machine.
  • Cassettes with high definition screens.
  • Processing facilities.
  • Immobilization and positioning aids: sandbags, foam wedges, tying tapes.
  • Protective clothing (lead-rubber aprons).

Ideal equipment

  • High output X-ray machine.
  • Rare earth high definition screens.
  • Automatic processing facilities.

Minimum consumables

  • X-ray film.
  • Pharmaceuticals for chemical restraint.

Preparation

Restraint

  • One to two competent people.
  • Sandbags.
  • Foam wedges.
  • Tying tapes.
  • Positioning trough.

Procedure

Core Procedure

Step 1 - Lateral

  • Position the patient in lateral recumbency on the side to be examined and immobilize.
  • Use a sandbag or tie to hold the contralateral limb caudally and dorsally away from the field.
  • Secure the affected limb in a cranial position but without undue distraction.
  • Use padding under the scapula and elbow as necessary to achieve a true lateral position of the humerus, parallel to the film.
  • Center the vertical beam at mid-shaft .
  • Collimate to include the elbow and the shoulder, as well as the soft tissues cranial and caudal to the shaft .

Step 2 - Caudocranial

  • Position the patient in dorsal recumbency in a trough and immobilize.
  • Extend the affected limb cranially and secure with a tie.
  • Rotate the thorax to ensure that the humerus is in a true caudocranial position .
  • In the likely event that the humerus is not horizontal, angle the beam until it is perpendicular to the shaft and elevate the cranial edge of the cassette to bring it as near perpendicular to the beam as possible.
    If an undistorted view of the elbow is important, opt for a craniocaudal projection.
  • Center the beam at mid-shaft.
  • Collimate to include both joints, and the lateral and medial skin surfaces.

Step 3 - Craniocaudal

  • Place the patient in dorsal recumbency, with a positioning trough at hip level, and immobilize.
  • Draw the affected limb caudally and secure with a tie.
  • Rotate the thorax to achieve a true craniocaudal position of the humerus.
  • Separate the limb from the thoracic wall with foam padding if necessary .
    The humerus will not lie horizontal in close apposition to the film. Obtain the position closest to horizontal and compensate for the increased object film distance by increasing the focal film distance.
  • Center mid-shaft.
    "Off-center" medially to project the humerus clear of the thoracic wall.
  • Collimate to include both joints and the lateral and medial skin surfaces .

Aftercare

Outcomes

Reasons for Treatment Failure

  • Inadequate sedation.
  • Poor technique: inaccurate positioning or centering, wrong exposure factors.
  • Poor processing.
  • Equipment failure.

Further Reading

Publications

Refereed papers