Felis ISSN 2398-2950

Radiology: appendicular skeleton (joints)

Contributor(s): Kate Bradley, Fraser J McConnell

Introduction

Overview

  • Skeletal radiography allows assessment of bone and, to a limited extent, soft tissue.

For lameness examination radiology should follow clinical examination and localization of the site of lameness.

Screening radiographs of the entire limb are unrewarding and may lead to erroneous diagnosis. They are indicated for evaluation of polyarthropathies and angular limb deformities.

Radiographic considerations

  • Detail screens and film combinations should be used for most examinations.
  • A low kV high mAs technique maximizes contrast.
  • Due to geometric effects of the diverging beam, radiography should be centered at the point of interest.

For angular limb deformities separate radiographs of adjacent joints should be taken (in addition to the entire limb) to allow joint evaluation without geometric distortion.

  • Orthogonal views are required as significant pathology, eg fractures, luxation may be missed on a single view.
  • In examination of suspected joint instability, eg ligament injury, 'stressed' views may be helpful.

This can be done by using sandbags and ties - manual restraint is not required.

Restraint

  • Radiography of joints usually requires sedation but some painful conditions may require anesthesia to facilitate positioning.
  • In trauma patients evaluation and treatment of concurrent thoracic, abdominal or CNS injury should be undertaken before skeletal radiography.

It is important to remember that not all causes of lameness cause radiological changes.

  • A normal radiograph in a lame animal should prompt consideration of:
    • Incorrect localization of lameness - repeat clinical examination.
    • Soft tissue injury - reconsider differential diagnosis.
    • Neurological disease, eg brachial plexus neoplasia, prolapsed intervertebral disc (PIVD) - reconsider differential diagnosis.
    • Radiolucent foreign body in foot - repeat clinical examination.
    • Early bone or joint disease before development of bony changes - repeat examination 2-4 weeks later.

Indications

  • Investigation of:
    • Lameness.
    • Limb swelling.
    • Limb deformity.
  • Survey radiography gives no information about articular cartilage in most cases.

Bone has a limited response to injury (lysis and/or new bone formation), therefore it is important to assess location of lesion, signalment and general medical history.

 

 

Interpretation

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