A plantar flexion response to nerve stimulation indicates needle misplacement in the epidural/spinal space during psoas compartment block.

We report two cases of plantar flexion due to epidural misplacement of the needle during psoas compartment block, providing a response feedback for needle position during this procedure. In one case, the response occurred contralaterally, and in the other bilaterally. In the first patient, the cause of contralateral plantar flexion could not be determined and no injection was made. In the second patient, the anteriorposterior-fluoroscopic image showed that the tip of the needle was placed at the midline of the column. At this point, 3 ml of radiopaque medium was injected, and it diffused throughout the epidural space. Subsequently, single-shot epidural anesthesia was achieved by injection through this needle.