Sacroiliac joint (PA sacrum view)
Disclosures
- updated 4 Sep 2022:
Nothing to disclose
Updates to Article Attributes
Body
was changed:
The posteroanterior sacrum projection is a useful part of the sacroiliac series and demonstrates the opened sacroiliac joint spaces and L5-S1 intervertebral joint space.
Indications
This view is useful in visualising any fractures, sacroiliac joint dislocations or subluxations, and possible inflammation (i.e. sacroiliitis) of the sacrum and/or sacroiliac joints. Due to the shallow obliquity of the sacroiliac joints, the prone position allows the diverging x-ray beam to project through the joint space giving better visualisation of the joint compared to the AP projection 1.
Patient position
- the patient is prone on the imaging table with legs extended
- patient’s shoulders and anterior superior iliac spines are at equal distances from the imaging table
Technical factors
- posteroanterior projection
-
centring point
- central ray midline at a level 1.5 cm below crest (at the level of posterior superior iliac spine)
- central ray with a caudal angle of 30°-35°
-
collimation
- laterally to include both sacroiliac joints
- superiorly and inferiorly to include the entire sacrum
-
orientation
- portrait
-
detector size
- 18 cm x 24 cm
-
exposure
- 75 kVp
- 20-30 mAs
-
SID
- 100 cm
-
grid
- yes
Image technical evaluation
- the sacroiliac joints are demonstrated open without foreshortening
- the sacrum should be free of foreshortening and the inferior segments of the sacrum should be overlapped over the symphysis pubis 2
- the mid-sagittal plane of the sacrum should be aligned with the symphysis pubis to ensure no rotation
Practical points
- when possible, imaging the sacroiliac joints in a posterior-anterior position is preferred in terms of demonstrating the sacroiliac joints and dose 3
- the sacroiliac joint runs in an oblique coronal orientation, PA imaging allows the diverging x-ray beam to project through the joint space, better visualising it compared to an AP projection
- due to tissue compression, the PA projection for sacroiliac joint imaging significantly lowers radiation dose compared to the AP projection without compromising image quality 3
-<p>The <strong>posteroanterior s</strong><strong>acrum</strong> projection is a useful part of the <a href="/articles/sacroiliac-series">sacroiliac series</a> and demonstrates the opened sacroiliac joint spaces and L5-S1 intervertebral joint space.</p><h4>Indications</h4><p>This view is useful in visualising any fractures, sacroiliac joint dislocations or subluxations, and possible inflammation (i.e. <a href="/articles/sacroiliitis">sacroiliitis</a>) of the <a href="/articles/sacrum">sacrum</a> and/or <a href="/articles/sacroiliac-joint">sacroiliac joints</a>. Due to the shallow obliquity of the sacroiliac joints, the prone position allows the diverging x-ray beam to project through the joint space giving better visualisation of the joint compared to the AP projection <sup>1</sup>.</p><h4>Patient position</h4><ul>-<li>the patient is prone on the imaging table with legs extended</li>-<li>patient’s shoulders and <a href="/articles/anterior-superior-iliac-spine">anterior superior iliac spines</a> are at equal distances from the imaging table</li>-</ul><h4>Technical factors</h4><ul>-<li><strong>posteroanterior projection</strong></li>-<li>-<strong>centring point</strong><ul>-<li>central ray midline at a level 1.5 cm below crest (at the level of posterior superior iliac spine)</li>-<li>central ray with a caudal angle of 30°-35°</li>-</ul>-</li>-<li>-<strong>collimation</strong><ul>-<li>laterally to include both sacroiliac joints</li>-<li>superiorly and inferiorly to include the entire sacrum</li>-</ul>-</li>-<li>-<strong>orientation </strong><ul><li>portrait<em> </em>-</li></ul>-</li>-<li>-<strong>detector size</strong><ul><li>18 cm x 24 cm</li></ul>-</li>-<li>-<strong>exposure</strong><ul>-<li>75 kVp</li>-<li>20-30 mAs</li>-</ul>-</li>-<li>-<strong>SID</strong><ul><li>100 cm</li></ul>-</li>-<li>-<strong>grid</strong><ul><li>yes</li></ul>-</li>-</ul><h4>Image technical evaluation</h4><ul>-<li>the sacroiliac joints are demonstrated open without foreshortening</li>-<li>the sacrum should be free of foreshortening and the inferior segments of the sacrum should be overlapped over the symphysis pubis <sup>2</sup>-</li>-<li>the mid-sagittal plane of the sacrum should be aligned with the symphysis pubis to ensure no rotation</li>-</ul><h4>Practical points</h4><ul>-<li>when possible, imaging the sacroiliac joints in a posterior-anterior position is preferred in terms of demonstrating the sacroiliac joints and dose <sup>3</sup>-</li>-<li>the sacroiliac joint runs in an oblique coronal orientation, PA imaging allows the diverging x-ray beam to project through the joint space, better visualising it compared to an AP projection</li>-<li>due to tissue compression, the PA projection for sacroiliac joint imaging significantly lowers radiation dose compared to the AP projection without compromising image quality <sup>3</sup>-</li>- +<p>The <strong>posteroanterior s</strong><strong>acrum</strong> projection is a useful part of the <a href="/articles/sacroiliac-series">sacroiliac series</a> and demonstrates the opened sacroiliac joint spaces and L5-S1 intervertebral joint space.</p><h4>Indications</h4><p>This view is useful in visualising any fractures, sacroiliac joint dislocations or subluxations, and possible inflammation (i.e. <a href="/articles/sacroiliitis">sacroiliitis</a>) of the <a href="/articles/sacrum">sacrum</a> and/or <a href="/articles/sacroiliac-joint">sacroiliac joints</a>. Due to the shallow obliquity of the sacroiliac joints, the prone position allows the diverging x-ray beam to project through the joint space giving better visualisation of the joint compared to the AP projection <sup>1</sup>.</p><h4>Patient position</h4><ul>
- +<li>the patient is prone on the imaging table with legs extended</li>
- +<li>patient’s shoulders and <a href="/articles/anterior-superior-iliac-spine">anterior superior iliac spines</a> are at equal distances from the imaging table</li>
- +</ul><h4>Technical factors</h4><ul>
- +<li><strong>posteroanterior projection</strong></li>
- +<li>
- +<strong>centring point</strong><ul>
- +<li>central ray midline at a level 1.5 cm below crest (at the level of posterior superior iliac spine)</li>
- +<li>central ray with a caudal angle of 30°-35°</li>
- +</ul>
- +</li>
- +<li>
- +<strong>collimation</strong><ul>
- +<li>laterally to include both sacroiliac joints</li>
- +<li>superiorly and inferiorly to include the entire sacrum</li>
- +</ul>
- +</li>
- +<li>
- +<strong>orientation </strong><ul><li>portrait<em> </em>
- +</li></ul>
- +</li>
- +<li>
- +<strong>detector size</strong><ul><li>18 cm x 24 cm</li></ul>
- +</li>
- +<li>
- +<strong>exposure</strong><ul>
- +<li>75 kVp</li>
- +<li>20-30 mAs</li>
- +</ul>
- +</li>
- +<li>
- +<strong>SID</strong><ul><li>100 cm</li></ul>
- +</li>
- +<li>
- +<strong>grid</strong><ul><li>yes</li></ul>
- +</li>
- +</ul><h4>Image technical evaluation</h4><ul>
- +<li>the sacroiliac joints are demonstrated open without foreshortening</li>
- +<li>the sacrum should be free of foreshortening and the inferior segments of the sacrum should be overlapped over the symphysis pubis <sup>2</sup>
- +</li>
- +<li>the mid-sagittal plane of the sacrum should be aligned with the symphysis pubis to ensure no rotation</li>
- +</ul><h4>Practical points</h4><ul>
- +<li>when possible, imaging the sacroiliac joints in a posterior-anterior position is preferred in terms of demonstrating the sacroiliac joints and dose <sup>3</sup>
- +</li>
- +<li>the sacroiliac joint runs in an oblique coronal orientation, PA imaging allows the diverging x-ray beam to project through the joint space, better visualising it compared to an AP projection</li>
- +<li>due to tissue compression, the PA projection for sacroiliac joint imaging significantly lowers radiation dose compared to the AP projection without compromising image quality <sup>3</sup>
- +</li>
Unable to process the form. Check for errors and try again.