Electrode positioning in thoracic percutaneous partial rhizotomy: an anatomical study

The present study was undertaken to clarify if needle positioning in percutaneous partial rhizotomy in the thoracic area based on bony landmarks and guided by fluoroscopic control leads to adequate placement in or at the targeted nervous tissue, i.e., the dorsal root ganglion (DRG), and to determine if needle localization by CT is more reliable than by fluoroscopic control. An investigation was performed in 2 cadavers, simulating the clinical setting as much as possible. At the levels T1-T8 a drill hole was made in the vertebral arc with a Kirschner wire. At the levels T9-T12 the "classic" dorsolateral technique was used. In 46 procedures the position of the needle tips was compared using hard copies of the fluoroscopic images, CT images at 1.5 mm intervals, surface photographs, and stained 25 microns sections obtained by a multirange heavy duty cryomicrotome. The position of the DRG in the foramen, and its size, were measured. In the sections, considered as the "golden standard", in 28 cases (60.9%) the needle tip was found in the DRG and in the extradural dorsal root in 14 cases (30.4%). In 4 cases (8.7%) no nervous tissue was encountered. In 8 of 32 "drill hole procedures" the facet joint was pierced. No accidental pleural puncture occurred in any of the procedures. The needle position was imaged more accurately by fluoroscopy. It is concluded that fluoroscopic control is a reliable guide to needle placement in percutaneous partial rhizotomy and permits standardization of the technique with the help of bony landmarks.