{"id":47683,"date":"2019-03-08T00:00:00","date_gmt":"2019-03-08T00:00:00","guid":{"rendered":"https:\/\/www.imv-imaging.com\/2019\/03\/improving-elbow-radiography-the-importance-of-positioning-and-exposure\/"},"modified":"2024-06-19T11:29:05","modified_gmt":"2024-06-19T11:29:05","slug":"improving-elbow-radiography-the-importance-of-positioning-and-exposure","status":"publish","type":"post","link":"https:\/\/www.imv-imaging.com\/en\/2019\/03\/improving-elbow-radiography-the-importance-of-positioning-and-exposure\/","title":{"rendered":"Improving elbow radiography – the importance of positioning and exposure"},"content":{"rendered":"\n

Read below: Improving elbow radiography<\/p>\n\n\n

Whilst the increasing accessibility of Computerised Tomography (CT) has reduced the use of plain film radiography in some practices, a well-positioned and correctly exposed set of elbow radiographs can provide important information and still holds an important role in the diagnosis of elbow joint pathology.<\/p>\n<\/p>\n

There are three standard projections: flexed mediolateral, extended mediolateral and cranio-caudal. Elbow anatomy is complex and failure to position the patient correctly or to perform a minimum of two orthogonal projections can lead to missed pathology or misdiagnosis.<\/p>\n

This article provides a refresher of elbow positioning during acquisition and assessment of images to check correct positioning has been achieved.<\/p>\n

Extended Mediolateral view<\/h3>\n

For all mediolateral projections the patient should be in lateral recumbency with the elbow to be imaged against the table and the contralateral forelimb pulled back and secured in retraction.<\/p>\n

The limb should be extended so that the elbow is cranial to the thorax and the angle between the humerus and radius\/ulna is 110\u02da, avoiding overextension. The radius and ulna should be parallel to the imaging plate, placing padding under the carpus is sometimes required to achieve this.<\/p>\n

Centre the X-ray beam on the palpable medial epicondyle of the humerus and collimate the beam to include the distal 1\/3rd<\/sup> of the humerus and proximal 1\/3rd<\/sup> of the radius\/ulna.<\/p>\n

\"Lateral<\/p>\n

Flexed Mediolateral view<\/h3>\n

This projection allows improved visualization of the anconeal process of the ulna compared with the extended mediolateral projection.<\/p>\n

The forelimb should be extended so that the elbow is positioned cranial to the thorax. In short-legged dogs it may be necessary to place a pad behind the elbow to push the leg cranially. The elbow should be positioned so that the angle between the humerus and radius\/ulna is 45\u00b0, avoiding over flexion.<\/p>\n

Centre on the medial epicondyle of the humerus and collimate the beam to include the distal 1\/3rd<\/sup> of the humerus and proximal 1\/3rd<\/sup> of the radius\/ulna.<\/p>\n

\"Lateral<\/p>\n

Cranio-caudal view<\/h3>\n

Position the dog in sternal recumbency with the limb to be imaged extended cranially. Large and deep-chested dogs may need to be positioned in a V-trough.  Ensure that the condyles of the humerus are equidistant from the imaging cassette or table. The contralateral limb should be in a flexed, neutral position with the head resting on top so that the head is not included within the radiograph. This can be tricky to achieve in dogs with short necks.  <\/p>\n

It can be helpful to use a radiolucent tie to prevent the elbow from rotating, a small piece of cotton wool under the elbow may also help.<\/p>\n

Centre the beam at the level of the humeral condyles and collimate to include the distal 1\/3rd<\/sup> of the humerus and proximal 1\/3rd<\/sup> of the radius\/ulna.<\/p>\n

\"CC<\/p>\n

Common issues<\/strong><\/h3>\n

Exposure<\/h3>\n

As with all orthopaedic radiography it is vital to ensure that the exposure factors used are correct. The most common error is to use too high a kV value and too low an mAs value. Whilst digital systems cope better with suboptimal exposure values than film systems, there is a risk of \u2018burning out\u2019 subtle lesions for example osteochondosis dissecans (OCD) lesions, small bone fragments or mild periarticular new bone formation.<\/p>\n

Using a lower kV improves visualization of subtle changes and the soft tissues, but it is vital to increase the mAs to compensate. Quantum mottle is caused by too low an mAs value and reflects a lack of photons reaching the detector. This will lead to a reduction in the amount of information available to create the radiograph and loss of trabecular detail.<\/p>\n

\"High<\/p>\n

On this CR image there are a number of issues, the most significant of which is the excessively high kV which has caused \u2018burn out\u2019 of the olecranon process of the ulna. There is some quantum mottling of the condyles of the humerus and poor trabecular pattern which indicates that the mAs is slightly too low.
<\/em>
To improve this image the kV should be reduced by around 10-15kV and the mAs should be increased.<\/em><\/p>\n

Incorrect extension\/flexion of laterals<\/h3>\n

If the degree of flexion or extension is not accurate further issues may result:<\/p>\n