Three-dimensional/four-dimensional volumetric ultrasound imaging of the sciatic nerve

Currently, there are limited data on the use of 3-dimensional ultrasound to image peripheral nerves. We undertook this imaging study to determine the feasibility of using 3-dimensional ultrasound imaging to delineate the anatomy of the sciatic nerve.

After research ethics committee approval and written informed consent, 4 healthy young adult male volunteers underwent 3-dimensional ultrasound scan of the sciatic nerve. A Voluson 730 Expert (GE Healthcare, Austria) with a broadband convex volume transducer (4-8.5 MHz) was used to scan the sciatic nerves at 3 levels: the subgluteal space, posterior aspect of the midthigh, and at the apex of the popliteal fossa. Three-dimensional volumetric ultrasound scan of the sciatic nerve was performed with the transverse plane as the data acquisition plane. The acquired 3-dimensional volumes were also rendered using a 3-dimensional volume-rendering software and displayed as a multiplanar image or as a "niche" display.

The right sciatic nerve was successfully scanned using the broadband convex volume transducer in all 4 volunteers. A distinct perineural space was identified around the sciatic nerve from the subgluteal space to the level of the popliteal fossa. Proximally, the sciatic nerve was visualized in a hypoechoic "subgluteal space" between the epimysium of the gluteus maximus and the quadratus femoris muscle. More distally, a hypoechoic "perineural" space was identifiable between the sciatic nerve and the hamstrings muscles. The niche view demonstrated the cranial extension of the subgluteal space, as an intermuscular tunnel or as a conduit for the sciatic nerve.

We have demonstrated that it is feasible to perform 3-dimensional ultrasound imaging of the sciatic nerve. The anatomic information obtained is more detailed than that with a 2-dimensional scan, which provides better insight into the spatial relationship of the sciatic nerve with its surrounding structures. A distinct "perineural space" was also identified alongside the course of the sciatic nerve, which may play a significant role in sciatic nerve blockade.