Spinal cord stimulation in chronic pain : a study of health outcomes and costs

Abstract: Background: The aetiology of chronic pain is complex and encompasses many different causes. Chronic pain commonly arises due to spinal disorders causing pain in the back and legs. Chronic pain is a substantial global public health problem, with a high prevalence, detrimental effects on health and health-related quality of life (HRQoL), ability to work and associated societal costs. Results from clinical studies indicate that spinal cord stimulation (SCS) decreases pain, improves HRQoL and disability, in patients with chronic pain of predominantly neuropathic origin, and has long been used in clinical practice. SCS, a minimal-invasive type of neuromodulation device (implant of electrodes in the epidural space), is commonly indicated for patients with intractable pain, who do not respond to prior treatments such as spine surgery. However, there is little known about the characteristics of patients receiving SCS in clinical practice, the long-term effects, and the potential influence of patient characteristics on treatment effects. The broader aim of the thesis is to investigate health outcomes and societal costs in patients with chronic pain treated with SCS. Methods: The studies were based on Swedish national register data. Study I investigated pre-and post-lumbar spine surgery costs, HRQoL, disability, and pain, in patients who received SCS treatment following lumbar spine surgery. The study was exploratory and included several health and cost outcomes in relation to initial lumbar spine surgery and subsequent SCS. HRQoL, pain, and disability were measured up to five years after spine surgery, and costs were measured three years before and after spine surgery and SCS, respectively. Study II analysed the impact of SCS on short-term sick leave and long-term disability pension and what explored potential predictors are associated with the impact. A matched reference group was used to control for societal changes that may impact usage of sickness benefits. Conclusions: Spine surgery preceding SCS did not have any effect on pain, HRQoL, and costs at one, two and five years in patients who were subsequently treated with SCS. Patients who subsequently received SCS after spine surgery were statistically significantly worse off in terms of disability and HRQoL already at the initial spine surgery. SCS, in patients with or without prior spine surgery, is associated with statistically significant decrease in sick leave days, but not disability pension which increased. SCS decreased the overall net disability days and consequently indirect cost in working age patients. Large productivity losses prior to SCS were demonstrated, indicating a significant burden on the employers, the patient, and the society at large. Usage of anti-depressants was significantly associated with poorer effect on disability days. Other socioeconomic and clinical factors had no association with the effect of SCS on sick leave and disability pension.