Single-puncture ultrasound-guided sciatic, femoral, and obturator injection (SP-SFO): Spread of dye in cadavers.

Background: The terminal nerves of the lumbar plexus, the femoral and obturator nerves, and the sciatic nerve are situated in different fascial planes on the medial side of the thigh. Attempts have been made to approach these nerves using a single puncture from the anterior and medial aspect of the thigh. The previously described SOFT block requires multiple transducer positions, needle redirections, and punctures. We attempted a novel single-puncture, single-position approach to all 3 nerves in different fascial planes in 6 soft embalmed cadavers that provided a total of 12 specimens.

Methods: Six fresh human cadavers left at room temperature for a minimum of 6 h were positioned supine, and an ultrasound-guided single puncture technique was used to target branches of the sciatic, femoral, and obturator nerves (SP-SFO) and inject 0.1% methylene blue dye. Cross-sections were obtained with a band saw in all cadavers at the level of the SP-SFO injections to observe the spread of the dye in various planes.

Results: Cadaver cross-sections showed the spread of the dye in all respective planes. The dye infiltrated the femoral and obturator nerves, while in 4 specimens it reached the sciatic nerve and the paraneural tissue.

Conclusion: This single puncture for branches of the sciatic, femoral, and obturator nerves block (SP-FSO block) can be used to successfully target all these nerves.