Dorsal Root Ganglion Stimulation Lead Fracture Within the Superficial Fascial Layers in 4 Cases

The fourth case is a 78-year-old man with chronic low back pain and left-sided radicular pain who failed multiple interventional procedures and was deemed a poor surgical candidate by his surgeon. He had DRG-S leads implanted at the bilateral T12 DRGs for his low back pain and a left S1 lead for his left leg pain. After implantation, his pain improved from 85/100 to 30/100 mm on VAS, and his ODI improved from 68 to 18. He returned 13 months after implantation with worsening left-sided low back pain. Interrogation of the DRG-S system revealed his left T12 lead had an impedance of >7000 Ω, and a fluoroscopic image identified a lead fracture close to where the lead likely originally had punctured the skin (Figure 2 C, D). He underwent surgical revision and had a restoration of the effectiveness of DRG-S therapy.

We described 4 cases of visible DRG-S lead fracture, which occurred adjacent to the puncture site at the skin. After DRG-S lead placement, the lead exits the epidural space and sequentially passes through the spinal ligaments, the erector spinae muscles, the deep thoracolumbar fascia (TLF), the deep adipose tissue (DAT), the membranous plane, superficial adipose tissue (SAT), and the skin. The membranous plane was previously referred to as the superficial, Scarpa’s, Camper’s, or Colle’s fascia. The subcutaneous tissue has since been renamed to the DAT and the SAT, separated by a membranous plane. This membranous plane surrounds the body, whereas the second layer, the deep fascia, surrounds the musculoskeletal system and separates it into fascial compartments. 9 – 12 Together, the TLF, DAT, membranous plane, and SAT create a sliding system between the skin and the muscles, allowing changes in external and internal stimuli and muscular activity to be disconnected from direct transmission between the muscles and the skin. 10 Fascial planes can respond to sensory input by contracting; by relaxing; or by adding, reducing, or changing their composition through fascial remodeling. 13 In response to physiologic stress or injury, fibroblasts secrete collagen and other proteins making the fascia’s composition thicker and less extensible. These changes potentiate the fascia’s tensile strength but may cause restriction of elements passing through the fascia. In the case of DRG-S leads passing through the fascia, such changes may potentially anchor the lead at this point. In our 4 cases, lead fractures occurred superficially, well above the deep fascial layer. The tunneled epidural implant technique we used involves standard DRG-S lead placement with an “S” tension loop (Figure 3 A), and then driving a Tuohy needle from the IPG pocket, traversing the DAT, through the membranous layer, and through the SAT to the paramedian skin puncture site (Figure 3 B). 7 Thus, in its final position, the lead passes from the pocket through the DAT, and as it nears the puncture site, it passes through the membranous plane, and then dips back down into the DAT and TLF to the epidural space, causing a small section of the lead to be trapped above the membranous plane in the SAP (Figure 3 C). This relatively acute bend may cause a focal area of tension and entrapment of the lead, potentially leading to friction and localized tension within the thin lead. In the cases we described, there was a clear separation of the fractured leads, indicating that the underlying wiring had separated, whereas, on explant, the lead casings were still intact. A similar phenomenon can be seen in focal nerve entrapments syndromes, as nerves traverse muscle, intermuscular septa, and fascia planes. This multiplanar course can cause an “internal stretch lesion” due to stress and tension on the nerve. 14 These types of injuries are often difficult to diagnose and can explain why traditional nerve release procedures may be inadequate in treating focal nerve injuries and require dissection of the fascia layers. 15 Previously used DRG-S lead placement approach. A, Planes of subcutaneous tissue with the Tuohy needle and lead placed. B, Tunneled epidural catheter technique for tunneling the lead to the pocket. Note the transection of the membranous layer. C, The lead is pulled between the membranous plane, potentially causing friction and focal areas of tension, ultimately damaging the lead. The tunneled epidural catheter technique, with or without a superficial stab incision at the skin, creates less tissue trauma, requires less suturing, and may potentially decrease infection risk. However, because of the potential risk of lead fracture, we have modified our implantation technique to abandon the approach above. As was demonstrated in these 4 cases, we believe the transection of membranous, or superficial fascial, plane can potentially contribute to lead fracture. Our updated implant technique utilizes an incision and anchoring of leads deep to the membranous plane, at all thoracolumbar levels. When passing the tunneling device, it should be performed toward the IPG pocket, as passing from the pocket to a smaller, superficial incision may still result in the lead crossing through the membranous plane. See Figure 4 for an ideal lead position. Passing the tunneling device deep to the membranous layer may avoid entrapment within the fascial plane. Lead fracture occurring in DRG-S not only results in loss of pain relief, but also leads to revision, replacement, or explantation of the device. Revision of DRG-S leads can be challenging technically, given the possible presence of adhesions, which increases the risk of further complications.

We described 4 cases of DRG-S lead fracture that we believe to be partially related to the technical component of the implant, which resulted in short lead sections experiencing tension due to fascial plane contraction. These cases suggest entrapment within the membranous plane of a thin DRG-S lead may be one of the potential causes for lead fracture, and thus, modification of the DRG-S implant technique should be considered to avoid interactions of the lead and this plane. Ongoing longitudinal surveillance of complications with DRG-S systems may help corroborate our observations.

Name: Kenneth B. Chapman, MD. Contribution: This author helped prepare the manuscript draft with important intellectual input from Kiran V. Patel, Noud van Helmond, and George C. Chang Chien. Conflicts of Interest: None. Name: Kiran V. Patel, MD. Contribution: This author helped edit the manuscript and approved the final version manuscript. Conflicts of Interest: Kiran V. Patel is a consultant and educator for Abbott Neuromodulation. Name: Noud van Helmond, MD. Contribution: This author helped edit the manuscript and approved the final version manuscript. Conflicts of Interest: None. Name: George C. Chang Chien, DO. Contribution: This author helped edit the manuscript and approved the final version manuscript. Conflicts of Interest: None. This manuscript was handled by: Mark C. Phillips, MD.

Our study design is limited by the fact that we are only describing 4 cases with limited long-term follow-up. Large prospective studies with long-term follow-up, in vivo dynamic biomechanics analyses, and real-world registry data could be helpful to elucidate the robustness of the proposed anchoring technique in mitigating future lead fracture risks. Our leads were all at the upper lumbar/lower thoracic region, and a larger pool of subjects could identify if the distance to the generator pocket plays a role. Additionally, DRG-S was used off-label in the present cases, since the only approved indication in the United States is complex regional pain syndrome. However, off-label use of DRG-S is common, 16 and retrospective series have specifically described the use of DRG-S for low back pain 1 and pelvic pain. 17