A simple approach for ultrasound-guided pararadicular injections in the sacral spine: a pilot computer tomography controlled cadaver study.

Aims: Injection therapies play an increasingly decisive role in the treatment of lower back pain. Cumulative studies could show the benefits of ultrasound-guided instillation procedures in the cervical and lumbar spine. We conducted this study to provide a new simple sonographic approach for pararadicular injections of the sacral spinal nerves and to prove the feasibility and accuracy by means of CT and anatomic dissection.

Material And Methods: Eight ultrasound-guided injections at four different levels of the sacral spine on a human ethanol-glycerol-embalmed cadaver (S1-S4) were performed. By means of sonography the sacral foramina were identified and the spinal needles were advanced in "in-plane technique" to the medial margin of the respective sacral foramen. Subsequently a solution of blue dye and contrast agent were injected. Then CT scans and anatomic dissection of the cadaver were performed to verify the correct placement of the needle tips and to visualize the dispersion of the injected solution in the respective compartment.

Results: Altogether a 100% success rate for a correct injection could be achieved. CT examination confirmed the correct placement of every needle tip within the intended compartment. Also, the anatomic dissections affirmed the appropriate needle positioning. Moreover, the blue dye dispersion was seen in the correct compartments and around the targeted spinal nerves.

Conclusions: Although this study was only performed on cadaveric models, this new sonographic approach for pararadicular injections in the sacral spine allows an easy, precise and unerring needle placement within the dorsal sacral foramen.