Pedometry as an External Measure of Spinal Cord Stimulation Patient Outcomes

Abstract

Chronic pain is a debilitating biologic and psychologic condition which affects nearly one third of the American population with an annual cost of $560 to $635 billion from associated health care costs and lost productivity. Treatment of chronic pain is difficult to objectively evaluate as it relies on subjective measure. An objective measure would be beneficial in assessing treatment efficacy and towards developing a closed loop system. We assess the efficacy of pedometry as an objective measure of treatment efficacy in spinal cord stimulation (SCS). Participants who had back and/or leg pain and were scheduled for permanent thoracic SCS implantation were offered inclusion. Preoperatively and at three months post-operatively, patients underwent a battery of tests including the Oswestry Disability Index (ODI), Pain Catastrophization Scale (PCS), McGill Pain Questionnaire-Short Form (MPQ), Likert Pain Scale, Visual Analog Scale (VAS), Insomnia Severity Scale (ISS), and Epworth Sleepiness Scale (ESS). They also wore a pedometer for 48 hours prior to SCS implantation and for 48 hours at three months. Walking distance, step count, and steps per hour were documented. Additionally, patients were asked to record their activity level in hours per day. Eight patients completed three month follow-up. All measurements of disability and pain decreased significantly: ODI (p = 0.004), PCS (p = 0.01), MPQ (p = 0.02), VAS (p = 0.001), ISS (p = 0.002), and ESS (p = 0.041). All pain and disability measurements decreased independent of activity measures, except lowest levels of pain at the patient's best. A positive correlation was found between improvement in participant's active time and improvement in ESS score, suggesting decreased daytime sleepiness with increased time spent active (r = 0.844, N = 7, p = 0.017). We demonstrate a mean improvement of more than 50% in distance walked, steps per hour, and total steps. Interestingly, total activity (number of hours spent active per day) was not dramatically improved. Our data suggests that as a group our patients' ambulation increased dramatically after successful SCS. The use of pedometry in conjunction with self-reporting can lend both quantitative and qualitative validity to pain, as well as allow objective assessment of efficacy of SCS in patients suffering from chronic low back and/or leg pain. Further, external sensors tracking these data may be a means of creating a closed loop system with SCS.