Spine

 Sacro Iliac Joints PA
Indications for imaging
Trauma, congenital abnormalities.

 

Anatomy  Demonstrated
 Sacro iliac joints.


Sacro Iliac Joints Anatomy

Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy Saunders, London

 

Basic Patient Position
 The patient lies prone on the table midline aligned to the midline of the table coronal plane parallel to the table, a support under the ankles to aid comfort.



 Sacro Iliac Joints PA Patient Position

Meschan, I. 1955 An Atlas of Normal Radiographic Anatomy Saunders, London

 
Radiation protection
There are many local rules for gonad protection however the following should be taken into account. The 28 day rule should be applied for female patients.
In males direct lead rubber gonad protection can be applied at all times
On small patients the omission of a grid will reduced the exposure.

 
Central Ray
The central ray is angles 20 degrees caudally and centered in the midline at the level of the posterior superior iliac spines, or the largest sacral prominence if palpable.
A sorter than normal FFD may help demonstrate the joints because of the greater divergent angle of the beam.
Exposure is made on suspended respiration.

 
Exposure Factors
Kv mAS FFD (cm) Grid Focus AEC Cassette
85 60 100 (75)( Yes Broad Yes 24 x 30 cm

 
Evaluation of the Image
 ID and markers must be present and correct in the appropriate area of the film
Evidence of collimation on four sides equally around the centering point.
Optimal exposure should penetrate all the bone structures and contrast should be low enough to visualise fully the bone and soft tissue structures.
Limits of the examination, the iliac bone surrounding the joint on all sides.
the lumbar sacral articulation should be projected open, the sacroiliac joints will appear open or nearly open.



 Sacro Iliac Joints PA Radiograph


Related Projections
Sacrum AP
Lumbar sacral articulation Lateral.
Sacro iliac joint obliques.

 
Additional modalities
CT
MRI