Providing Guidance on Safe Physical Therapy for Patients With Spinal Cord Stimulators: A Call to Action

A fundamental goal of chronic pain management is ensuring patients stay functionally and physically active despite their pain. Spinal cord stimulation (SCS) has been used since 1967 to help manage neuropathic pain conditions, such as complex regional pain syndrome and failed back surgery syndrome.1 SCS involves placing electrodes at specific anatomical levels in the epidural space correlating to a patient’s pain location. Depending on the electrode type, these electrodes are secured either with strain relief loops or anchors directly sutured into the spinal fascia, and resulting scar tissue formation eventually further holds them in place. The electrodes are connected subcutaneously to an implantable pulse generator placed in the gluteal/flank region that delivers electrical signals to modulate pain pathways in the spinal cord and brain.1 The location of these electrodes is very important for the success of this therapy, and movement of these electrodes can result in loss of therapy effectiveness, with potential need for repeat invasive revision surgery. Electrode migration or fracture is a common complication associated with SCS, with rates reported to be as high as 21.4% and 7%, respectively.2 Migration or fracture can occur for many reasons, with adverse and inadvertent positional movements of the spine being an important risk factor.3 SCS, in conjunction with physical therapy, has demonstrated significant clinical and cost effectiveness compared with conventional medical management alone in the failed back surgery syndrome and complex regional pain syndrome patient populations.4,5 For physical therapy to be offered safely to patients with a spinal cord stimulator, it is imperative patients are provided clear, evidence-based instructions as to what physical activities and/or movements are safe to resume after device implantation and when in the recovery period it is safe. Guidelines on how to do this safely, however, have not been formally established, nor are there any suggestions provided by the Neuromodulation Appropriateness Consensus Committee via the International Neuromodulation Society. A recent publication identified no literature to date addressing the use of physical therapy in patients with implanted spinal cord stimulators.6 We aim to provide a call-to-action for rehabilitation specialists (both physical therapists and physicians) to determine which activities/movements are+ safe from a biomechanical perspective, and when in the postoperative course they are safe to resume, to minimize the rate of lead migration and/or fracture and ensure therapy efficacy. To act on this call-to-action, it is important to understand where the limitations and gaps exist in this area. One area that is unclear is how much electrode movement occurs within the epidural space through the range of motion of the cervical, thoracic, and lumbar spine with an electrode sutured to the spinal fascia. Clinical and radiological investigations of the degree of thoracic spine extension with arm movement also demonstrate the thoracic spine can extend up to 20 degrees; however, it is unclear if this is significant enough to contributed to lead dislodgment or fracture.7 Alterations in the epidural space when moving from the supine to upright position are assumed, and this likely has implications on electrode displacement based on observed changes in voltage requirements for SCS when moving from supine to standing/sitting positions.8 The degree and significance of these alterations has yet to be established, however. There may also be variations among SCS manufacturers with regard to electrode technology and composition; however, advances in electrode technology have improved their design to mitigate fracture. One area of need are studies evaluating the tensile strength of these electrodes to determine which movements specifically increase the risk of lead fracture. Further, the effects of truncal rotation and potential epidural space movement have not been studied. Live x-ray and/or cadaveric studies examining epidural electrode displacement could be conducted to determine how one could move from supine to upright positions and vice versa to minimize electrode displacement and more readily quantify cervical/thoracic spine movement. This would help improve the quality of instructions provided to patients about movements that are safe in the initial implant period. Home exercise programs that recognize this degree of mobility would be very useful to provide patients in the postoperative period. Another gap in our understanding is when physical activity is safe to resume, which is largely extrapolated from principles of tissue healing. Animal models suggest tissue wound bed strength increases after 3 weeks due to alignment of new collagen fibers and crosslinking.9 The strength of tissue wound beds reaches 70% at 6 weeks and 80% to 90% at full maturation, which can occur anywhere between 2 and 6 months with muscle and longer with ligament and tendon.9,10 It has also been suggested that scar tissue is responsive to remodeling and adaptation for up to 14 weeks.10 Based on these principles, our understanding of when physical therapy can safely resume is conservatively estimated to occur after 14 weeks, when scar tissue can adequately form and minimize electrode movement. Given the immediate relief patients can feel within hours and days after their spinal cord stimulator implant, there can be some enhanced motivation from patients to quickly resume physical activities that were previously challenging for them to do, which makes counseling patients on the need for patience immediately post procedure crucial. Thus, the gradual return to activity and specific types of exercise (isometric, isotonic, patterned, core strengthening, and cardiovascular programs) prescribed through the recovery period should be investigated and outlined in a stepwise fashion to not only prevent lead migration/fracture but also reactivation injury. The importance of physical therapy for patients with chronic pain cannot be overstated. Spinal cord stimulators are one tool as part of a biopsychosocial model in patients’ overall recovery, and the need for careful, cautious instructions becomes more important as SCS becomes more commonly utilized. We look forward to working with rehabilitation specialists in the community to quantify and establish these concrete recommendations to improve the quality of care provided. Concept/idea/research design: V. Varshney, J. Osborn Writing: V. Varshney, J. Osborn Consultation (including review of manuscript before submitting): J. Osborn There are no funders to report for this work. The authors completed the ICMJE Form for Disclosure of Potential Conflicts of Interest and reported no conflicts of interest.

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