EFFICACY AND PHARMACOECONOMICS STUDY OF SPINAL CORD STIMULATION (SCS) CONDUCTED AT THE PAIN THERAPY HUB, SAN GIULIANO HOSPITAL ASL NAPOLI 2
Authors: Filoso Immacolata , Iacolare Maria Rosaria , Monti Ida , Tortora Attilio , Contiello Claudio , De Luca Assunta , Scarano Anna , Gerbi Giovanni , Mignano Gaetano , Falconio Lucio Marcello 
Published: October 2023

Introduction:
Chronic Pain has been recognized by the World Health Organization as one of the major global public health issues. The condition has debilitating consequences from physical, psychological, and socio-relational perspectives due to its highly disabling nature. Spinal Cord Stimulation (SCS) involves the placement of one or more electrodes in the epidural space through surgical means, connected to a fully implantable battery that electrically stimulates the spinal nerve structures. This treatment is indicated for patients suffering from intractable chronic pain in the trunk and limbs, particularly demonstrating efficacy in treating neuropathic pain. This method has been in use since the mid-1970s. The study lasted 24 months, with the initial 8 months involving patient recruitment and the subsequent 16 months devoted to the follow-up period. Its purpose was to evaluate the cost-benefit ratio of SCS in patients with chronic pain, treated at the Pain Therapy Hub of San Giuliano Hospital, ASL Napoli 2 Nord. The primary goal was to assess the effectiveness of Spinal Cord Neurostimulation (SCS) when applied to these patients. By conducting a comparative assessment 16 months after the implantation, the study evaluated the reduction in pain and disability among patients treated with SCS. Additionally, the study analysed the costs incurred by the National Health Service (SSN) and the corresponding benefits achieved in treating patients with chronic pain using SCS. The study is aimed to assess the effectiveness of this treatment in terms of improving patients' health status and quality of life. Materials and Methods: The observational study is retrospective and single cantered, conducted at the regional Pain Therapy Hub of San Giuliano Hospital, ASL Napoli 2 Nord. The study lasted for 24 months, with the initial 8 months dedicated to patient recruitment and the subsequent 16 months for the follow-up period.A total of 39 adult patients capable of managing or tolerating the devices used in SCS were recruited. These patients had a diagnosis of chronic back and/or leg pain and were non-responders to pharmacological therapy and other therapeutic treatments. The patients were provided with information about this study.Sixteen patients were excluded due to psychological or psychiatric disorders, progressive neurological conditions, or being recipients of an intrathecal pump for pain-relief drug infusion or an IPG. The remaining 23 patients received the implantation of a pulse generator and two electrode catheters. This group constituted our cohort, to which questionnaires were administered to evaluate the level of disability using the Oswestry Disability Index (ODI) and pain measurement using the Visual Analog Scale (VAS). Data were collected at Time 0 (T0) and during the subsequent 16 months from the start of treatment (Follow Up). Only 4 out of the 23 patients removed the neurostimulator before the 16-month term due to incompatibility. Quality of life data related to health status were collected through parameters used to measure how health impacts physical, psychological, and emotional well-being (HRQoL). Additional informative sheets, in addition to the ODI, were administered both at Time 0 and at the Follow-Up point, with the intent to verify if changes in ODI corresponded to changes in HRQoL parameters. Furthermore, quantification of data on resource consumption attributable to costs borne by the National Health Service was conducted, related to the treatment of individuals with chronic pain. These costs were divided into costs related to hospitalization, materials and devices used during the implantation procedure, and instrumental and professional resources employed to carry out the procedure (direct costs), as well as those linked to specialist visits, medication use, instrumental and diagnostic analyses (indirect costs). Regarding direct costs at Time 0, the average costs of daily hospitalization in Campania were considered, along with the average costs of tools, equipment, instrumental and pharmacological resources for an SCS implantation procedure. The gross costs associated with professional resources involved in the procedure, with an average duration of two hours (anaesthesiologist, radiological technician, operating physician, and nurse), were also considered. Lastly, non-medical costs generated by personal habits of patients with chronic pain and their care and management were considered. These costs vary depending on the patient's general conditions. Generally, these are individuals with limited autonomy, leading to increased specialized care needs and subsequent rising costs, including decreased productivity due to absences from work and those temporarily dedicated as caregivers. All medical and non-medical costs were assessed one year before and 16 months after the implantation procedure, the latter being normalized to a 12-month period for equal evaluation periods. Results: The study examined 23 out of 39 eligible patients, evaluating the cost-effectiveness and cost-utility ratio of SCS over a period of 12 months before the implantation and 16 months after the spinal cord neurostimulator implantation. Among the 23 recruited patients, 4 did not reach the 16-month follow-up as they had their spinal cord neurostimulator removed. Two patients removed it due to infection, while the remaining two patients could not tolerate the implanted device. Out of the 19 patients included in the analysis, those who had shown poor quality of life and low health levels in the twelve months prior to the device implantation displayed a significant increase in clinical outcomes at the 16-month mark after SCS intervention. Analysing data related to the Oswestry Disability Index (ODI) and Visual Analog Scale (VAS) between T0 and Follow-Up, variations in disability levels for different groups were identified. The decrease in disability and pain perception corresponds to an increased quality of life for the patient and a reduction in the social costs of the disease. The utility index Eq-5D increased from 0.45 to 0.68, and a noticeable improvement began to be observed after six months post-intervention.In terms of economic aspects, analysing monthly and annual medical and non-medical costs incurred by patients with chronic pain in conjunction with the direct and indirect costs of the SSN intervention shed light on the substantial expense to support therapies for this condition, borne by both the SSN and the patient. Nonetheless, these costs are to be considered one-time expenditures, such as those related to the implanted device and its procedure, or significantly reduced, like specialist visits and medication usage, due to the patient's improved health condition. Comparing costs one year before and 16 months after the intervention borne by the SSN highlighted reductions in certain categories in the final amount. Specifically, the number of diagnostic tests and tutoring expenses dropped to zero, while check-up visits reduced on average to two per year.Similarly, when comparing non-medical costs incurred by the patient one year before and 16 months after the intervention, a significant decrease in the final amount was recorded, correlating with the overall improvement in health status and the resulting reduction in the frequency and costs of accessing individual requested services. A notable increase in SSN expenditure was observed within the first 6 months after the neurostimulator implantation, primarily attributed to the device's cost and related implantation procedures. By 9 months post-implantation, a reduction in SSN expenses compared to the pre-implantation months could already be observed.