When performing the PA oblique projection of the SC joints which joint would be demonstrated?

Citation, DOI & article data

Citation:

Murphy, A., Fahrenhorst-Jones, T. Sternoclavicular joint (anterior oblique views). Reference article, Radiopaedia.org. (accessed on 08 Sep 2022) https://doi.org/10.53347/rID-54318

The anterior oblique projections of the sternoclavicular joints are complimentary to the front on PA view in the sternoclavicular joint series

The side of obliquity pertains to the joint of interest i.e. RAO to assess the right sternoclavicular joint. However, this projection is often performed bilaterally, subsequently, this article will describe the projection as a bilateral examination.  

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The oblique positioning maneuvers the join of interest away from central structures to produce a clearer view of articulation. It is often requested in the context of significant trauma that can result in sternoclavicular joint dislocation or medial end clavicular fractures. Furthermore, this projection can be requested when following up on already known sternoclavicular injuries in the setting of outpatient appointments. 

• the patient is preferably laid prone with a 10 to 15-degree anterior oblique rotation this is normally achieved with a wedge sponge helping the patient maintain position.
• a bilateral examination will require the patient to lay RAO and LAO for separate projections 
• this examination can be performed erect if the patient is stable

• posteroanterior anterior oblique projection
• centering point
  • centered at the level of the second to third thoracic vertebra at the midline
  • 2-5 cm lateral from the midline toward the raised side (relative to detector i.e. LAO would favor centering laterally towards the right)
• collimation
  • laterally to include the medical third of both clavicles 
  • inferior to include the sternoclavicular joints and part of the manubrium 
  • superior to include the entirety of the sternoclavicular joint
• orientation  
  • landscape
• detector size
  • 24 cm x 18 cm
• exposure
  • 60-70 kVp
  • 10-30 mAs
• SID
  • 100 cm
• breathing
  • suspended expiration
• grid
  • yes (this can vary departmentally)

• the sternoclavicular joint of interest will be central to the image without foreshortening 
• the opposite join will appear foreshortened and obscured by the bony thorax 

• the most challenging aspect when performing this projection is collimation; collimation must be tight to avoid scatter thus decreasing the image quality. Time should be taken to ensure the image is collimated appropriately.
• this projection is often performed bilaterally for comparison, it's important to remember that the side of interest will be the obliquity of the oblique
  • RAO evaluates the right sternoclavicular joint
  • LAO evaluates the left sternoclavicular joint
• the projection can be performed erect, be wary of the patient's movement

References

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