Patient Positioning:
The patient is placed in a prone position with the heels rotated laterally and a cushion pillow is used as an iliac wedge to facilitate the exposure of the skin surface in the coccygeal area.
Probe Positioning:
Use a transverse image for the sacral hiatus and dorsal sacrococcygeal ligament between the bilateral sacral cornua first, then rotate the probe by 90 ° to show the longitudinal view of the sacral hiatus.
After usual sterile preparation, patient is scanned with a linear array transducer to identify the sacral hiatus and sacrococcygeal ligament. Use a transverse image for the sacral hiatus and dorsal sacrococcygeal ligament between the bilateral sacral cornua first, then rotate the probe by 90 ° to show the longitudinal view of the sacral hiatus. Perform the injection by injetion through the skin and the dorsal sacrococcygeal ligament a few millimeters caudal to the probe using an in plane technique (needle is parallel to the probe).