Staggered transverse tripoles with quadripolar lateral anodes using percutaneous and surgical leads in Spinal Cord Stimulation (SCS)

Background: In spinal cord stimulation (SCS) for low-back pain, the use of electrode arrays with both low power requirements and selective activation of target dorsal column (DC) fibers is desired. The aligned transverse tripolar lead (TTL) configuration offers the best DC selectivity. Electrode alignment of the same configuration using three parallel percutaneous leads is possible, but compromised by longitudinal migration, resulting in loss of DC selectivity. This loss might be repaired by using the adjacent anodal contacts on the lateral leads. Objective: To investigate if stimulation using adjacent anodal contacts on the lateral percutaneous leads of a staggered transverse tripole can restore DC selectivity. Methods: Staggered transverse tripoles with quadripolar lateral anodes were modeled on the low-thoracic vertebral region (T10-T12) of the spinal cord using (a) PERC QD and (b) LAM QD, of same contact dimensions. The commercial LAM 565 surgical lead with 16 widely spaced contacts was also modeled. For comparison with PERC QD, staggered transverse tripoles with dual lateral anodes were modeled using PERC ST. Results: The PERC QD improved the depth of DC penetration and enabled selective recruitment of DCs as compared to PERC ST. Medio-lateral selectivity of DCs could not be achieved with the LAM 565. Conclusion: Stimulation using PERC QD improves anodal shielding of DRs and restores DC selectivity. Based on our modeling study, we would hypothesize that, in clinical practice, LAM QD can provide an improved performance compared to the PERC QD. Our model also predicts that the same configuration realized on the commercial LAM 565 surgical lead with widely spaced contacts can not selectively stimulate DCs essential in treating low-back pain.