Lumbar CT-guided radiofrequency ablation of the medial branch of the dorsal ramus of the spinal nerve. Anatomic study and description of a new technique

The success of radiofrequency ablation (RF) of the medial branch of the dorsal ramus in patients with facet joint pain depends on the effective coagulation distance. To date, computed tomography(CT)-guided techniques do not reach the nerve in parallel but rather than punctually. We report a new CT-guided technique to enhance parallelism and proximity of the RF needle to the nerve. Two examiners with different experience with CT-guided procedures in corpses performed all punctures at the lumbar spine on 10 corpses. A RF needle was inserted 1aEuro<overline>cm lateral to the spinous process of the vertebra located caudal to the target nerve. The needle was advanced under CT guidance at a flat angle between the superior articular process and the base of the costal or transverse process of the cranial vertebra. The position was verified by dissection. Needle position was judged successful provided the needle could be positioned in the first attempt with no more than one angle correction. In 86 out of 100 possible cases (50 per side) at the 5 lumbar segments, the RF needle could be depicted by CT in the target area with no more than one correction of the needle position. Anatomical dissections revealed that 47 out of 86 needles (54.6%) fulfilled the requirements of parallelism and proximity to the nerve. The dorsal ramus was never reached by the RF needle. Higher success rates were obtained in the middle segments compared to the border segments of L1-L2 and L5-S1. We could demonstrate that the principle of parallelism and proximity of the needle to the nerve could be fulfilled with this new technique; however, needle positioning requires practice due to the oblique puncture direction.