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World Neurosurg. 2018 Mar;111:e418-e423. doi: 10.1016/j.wneu.2017.12.079. Epub 2017 Dec 21.

Visualization of Needle-Tip Localization by Ultrasound Guidance with Contrast Bubble in Lumbar Selective Nerve Root Block: Clinical Pilot Study.

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Neurosurgery Division, Surgery Department, Faculty of Medicine Ramathibodi Hospital, Mahidol University, Bangkok, Thailand.
Department of Anesthesiology, Phramongkutklao Hospital, Bangkok, Thailand. Electronic address:



Epidural steroid injection for low back and leg pain has been shown to result in a positive clinical outcome. Lumbosacral selective nerve root block (SNRB) via a transforaminal approach is commonly performed under fluoroscopic guidance. However, ultrasound guidance is an alternative to overcome the radiologic disadvantages. This study examined the accuracy of needle-tip localization under ultrasound guidance with a contrast bubble, compared with fluoroscopic guidance.


The primary objectives were to envisage the needle-tip localization with an air bubble by ultrasound and also to determine the accuracy of needle-tip location in transforaminal lumbar SNRB for low back and leg pain patients who were not surgical candidates.


A prospective study of 30 SNRBs was conducted. An air bubble was produced and was used to envisage the needle-tip location under ultrasound guidance. Finally, the needle tip was confirmed by fluoroscopy. The accuracy of needle-tip location was statistically analyzed.


Twenty-four SNRBs were performed at L4-5 and 6 SNRBs at L3-4. The accuracy of needle-tip localization was 80%.


In order to avoid radiation exposure during the SNRB procedure, ultrasound guidance might be an alternative. Despite being accepted practice, there is a steep learning curve involved in the use of ultrasound guidance for lumbar SNRB, and proper training is crucial. A contrast bubble is a prospective enhancement for better visualization of ultrasound guidance.


Lumbosacral region; Needles; Nerve block; Pain; Spinal injection; Triamcinolone

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