Comparison of Classic Block and Sub-Branch Block During Sono-Guided Obturator Nerve Blocks: A Randomized Clinical...

The obturator nerve block (ONB) is commonly performed using anterior and posterior branch blocks at the inguinal crease level. However, in practical situations, we have found that variable adductor muscle twitching can remain even after a successful main branch block.

This study evaluates how much an additional twitching block affects the complete adductor motor block compared to the classic ONB. Additionally, the study analyzes the patterns of residual twitching sites.

A randomized, controlled trial.

The Department of Anesthesiology and Pain Medicine at the Gachon University Gil Medical Center.

In the classic group (n = 35), posterior and anterior branch blocks were performed by ultrasound with a nerve stimulator at the inguinal crease. In the sub-branch group (n = 35), the main branch block was performed in the same way as in the classic group. Fifteen minutes later, additional twitching blocks were performed. The primary outcome was the extent of the obturator reflex-graded adductor motor block, which was measured 15 minutes after the ONB in both groups, and the secondary outcome was the analysis of twitching site patterns.

The total dose of local anesthetic was higher in the sub-branch group, but the quality of obturator reflex grading was statistically significantly better than in the classic group. No patient in either group required general anesthesia to complete surgery. Residual twitching was usually observed in the adductor brevis, adductor magnus, or pectineus muscles or at the inner portion of the fascial line through which the anterior or posterior branch passed.

The success of the ONB was evaluated using obturator reflex grades, which might not have provided an accurate measure of success.

Although a main branch block alone does not usually result in inadvertent adductor muscle contraction severe enough to cause complications such as bladder perforation, partial residual muscle movement is observed. Therefore, supplementing the main branch block with an additional sub-branch block can be a reasonable strategy to achieve more complete motor blockade.