Quantification of Needle Angles for Traditional Lumbar Medial Branch Radiofrequency Ablation: An Osteological Study

Abstract

Background Clinical outcomes following lumbar medial branch radiofrequency ablation (RFA) have been inconsistent. One possible reason is less-than-optimal placement of the electrode along the medial branch at the lateral neck of superior articular process (SAP). Needle angles that define optimal placement (i.e., parallel to the medial branch) may be helpful for consistent technical performance of RFA. Despite its importance, there is a lack of anatomical studies that quantify RFA needle placement angles. Objective To quantify and compare needle angles to achieve parallel placement along the medial branch as it courses on the middle two-quarters of the lateral neck of the SAP at the L1-L5 vertebrae. Design Osteological Study Methods Ten lumbar vertebral columns were used in this study. Needles were placed along the periosteum of the middle two-quarters of the lateral neck of SAP. Mean needle angles for L1-L5 were quantified and compared using posterior (n = 100) and lateral (n = 100) photographs. Results Mean needle angles varied ranging from 29.29 ± 17.82° to 47.22 ± 16.27° lateral to the parasagittal plane (posterior view) and 33.53 ± 10.23° to 49.19 ± 10.69° caudal to the superior vertebral endplate (lateral view). Significant differences in mean angles were found between: L1/L3 (p =0.008), L1/L4 (p=0.003), and L1/L5 (p=0.040) in the posterior view and L1/L3 (p=0.042), L1/L4 (p<0.001), L1/L5 (p<0.001), L2/L4 (p=0.004), and L2/L5 (p=0.004) in lateral view. Conclusions Variability of needle angles suggest a standard “one-size-fits-all” approach may not be the optimal technique. Future research is necessary to determine optimal patient-specific needle angles from a more detailed and granular analysis of fluoroscopic landmarks.

3. Pain originating from the lumbar facet joints

“…5 Inserting electrodes at an oblique and cephalad angle results in a larger active tip-bony target interface and therefore greater chance of nerve capture, but the precise angle that optimizes electrode contact has yet to be determined (and may differ based on individual anatomy). 121 Although indirect results of randomized trials also support a nearparallel approach, these results should be interpreted with caution considering the differences in patient selection, criteria for designating the diagnostic/prognostic blocks as positive, and other technical parameters. 119…”

“…Strict parallel placement to the nerve can theoretically produce the largest lesions, though it is important that sensory thresholds are tested because if the electrode is placed exactly parallel to but adjacent to the nerve outside of the lesion circumference, it can miss it altogether 5 . Inserting electrodes at an oblique and cephalad angle results in a larger active tip‐bony target interface and therefore greater chance of nerve capture, but the precise angle that optimizes electrode contact has yet to be determined (and may differ based on individual anatomy) 121 . Although indirect results of randomized trials also support a near‐parallel approach, these results should be interpreted with caution considering the differences in patient selection, criteria for designating the diagnostic/prognostic blocks as positive, and other technical parameters 119 …”