Note: Please see pages ii , iii for a list of anatomic terms/abbreviations used throughout this book.

Trajectory View: The Trajectory/Anteroposterior View Is Also a Multiplanar View

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  Confirm the level (with the cross-table lateral view) by noting any visible landmarks (e.g., the coccygeal cornu, the sacrococcygeal joint, or any intracoccygeal joints) through which the approach may be planned. Mark this site with a skin marker or a metallic pointer. This demonstrates how superior or inferior the block should be initiated.

  
  
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  The C-arm is then brought to the AP position, and the needle is inserted in the midline at the predetermined superoinferior position, just deep enough to obtain skin purchase and to maintain a perpendicular trajectory needle position “down the beam.”

  
  
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  Cephalad or caudad tilt of the image intensifier to “line up” the disc space for entry ( Fig. 8A.1 ). Pre-procedure review of the lateral X-ray, CT or MRI image can help predetermine the best C-arm tilt angle such that the beam (and needle) passes parallel to the joint space. ).

  
  

  
  

  
  

  

  
  

  
  

  A, Fluoroscopic image of a trajectory view with the needle in position at the sacrococcygeal junction and in line to enter through the center of the disc. B, Radiopaque structures, trajectory anteroposterior view. C, Radiolucent structures, trajectory anteroposterior view.

  
  

Notes on Optimal Needle Positioning in the Multiplanar Trajectory/Anteroposterior View

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  This view should be used only to assess the mediolateral and superoinferior needle position. It should not be used for any substantial ventral needle advancement.

  
  
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  Direct the needle midline to access the ganglion impar.

Trajectory/Anteroposterior View Safety Considerations

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  If the needle strays from the midline, it may potentially cause the inadvertent blockade of other pelvic nerves or rectal perforation.

Optimal Needle Positioning in Multiplanar Imaging

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  The two views for needle advancement are AP and lateral.

  
  
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  The C-arm can remain in the lateral view throughout most of the procedure, except for briefly checking an the AP view to confirm that the needle tip, the contrast, or both have appropriate midline placement. The AP view can be especially helpful if the lateral view shows a contrast flow pattern that is suboptimal or atypical.

Optimal Needle Positioning in Multiplanar Imaging

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  The two views for needle advancement are AP and lateral.

  
  
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  The C-arm can remain in the lateral view throughout most of the procedure, except for briefly checking an the AP view to confirm that the needle tip, the contrast, or both have appropriate midline placement. The AP view can be especially helpful if the lateral view shows a contrast flow pattern that is suboptimal or atypical.