Accuracy of needle-tip localization by ultrasound guidance lumbar selective nerve root block: a prospective clinical study of 78 lumbar nerve roots block.

Objective: Selective nerve root block (SNRB) is the accepted procedure for diagnostic and therapy in lumbar radicular back pain management. The present study was to determine the accuracy of needle-tip under ultrasound guidance subsequently confirmed with fluoroscopy in patients who underwent SNRB. To date, no study comparing these two techniques has been performed.

Methods: After the IRB approval, a prospective trial was conducted to determine the accuracy of ultrasound guidance SNRB in 40 consecutive patients with lumbar radicular pain undergoing fluoroscopic guidance SNRB between January 2010 and January 2011. Firstly, needle-tip was located at the desired optimal landmark under ultrasound guidance and then subsequently fluoroscopic confirmation of needle-tip position was done. Finally, the injection was performed as usual. The primary outcome was the accuracy of needle-tip placement comparing between under ultrasound and subsequently fluoroscopic confirmation. The secondary outcome was the associated factors of the accuracy of needle-tip under ultrasound guidance.

Results: Seventy-eight lumbar nerve roots were injected in the patients that underwent SNRB under fluoroscopic guidance. The accuracy of needle-tip on each lumbar nerve root under ultrasound guidance with fluoroscopic confirmation ranged from 7.14% to 80.95%. Mean of the accuracy of needle-tip under ultrasound guidance comparing with subsequently fluoroscopic confirmation was 62.82% while 95% CI ranged from 51.13 to 73.50%. The age older than 65 years old was significantly associated with the poor accuracy under ultrasound guidance (p-value = 0.0095).

Conclusions: To position the needle-tip under ultrasound guidance is feasible and has good safety profile. The accuracy could be achieved individually. However, because the accuracy of ultrasound guidance technique depends on the operator a steep learning curve and larger prospective clinical study is needed.