Effect of Spinal Cord Stimulation on Early Disability Pension in 198 Failed Back Surgery Syndrome Patients: Case-Control Study

RESEARCH—HUMAN—CLINICAL STUDIES Hanna Kaijankoski, MD∗ Effect of Spinal Cord Stimulation on Early Disability Pension in 198 Failed Back Surgery Syndrome Patients: Case-Control Study Mette Nissen, MD‡ Mikael von Und Zu Fraunberg, MD, PhD‡ Olavi Airaksinen, MD, PhD∗ Jukka Huttunen, MD, PhD‡ ∗ Department of Physical and Rehabilitation Medicine, Kuopio University Hospital (KUH), and Faculty of Health Sciences, School of Medicine, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland; ‡ Department of Neurosurgery, Kuopio University Hospital (KUH), and Faculty of Health Sciences, School of Medicine, Institute of Clinical Medicine, University of Eastern Finland, Kuopio, Finland The abstract was presented at the TESC competition held by 21st European Congress of Physical and Rehabilitation Medicine in Vilnius, Lithuania on May 2, 2018. Correspondence: Hanna Kaijankoski, MD, Department of Physical and Rehabilitation Medicine, Kuopio University Hospital, PL 100, 70029 KYS, Finland. E-mail: Received, June 1, 2018. Accepted, October 9, 2018. Published Online, November 26, 2018.  C Congress of Neurological Surgeons 2018. This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs licence (http://creativecommons.org/ licenses/by-nc-nd/4.0/), which permits non-commercial reproduction and distribution of the work, in any medium, provided the original work is not altered or transformed in any way, and that the work is properly cited. For commercial re-use, please contact NEUROSURGERY BACKGROUND: Spinal cord stimulation (SCS) has proven to be a cost-effective treatment for failed back surgery syndrome (FBSS). However, the effect on patients’working capability remains unclear. OBJECTIVE: To evaluate the impact of SCS on working capability and to identify the factors behind permanent disability in FBSS patients. METHODS: The study group consisted of 198 working-age patients with SCS trialed or implanted for FBSS in a single center between 1996 and 2014. For each patient, 3 living controls, matched by age, gender, and birthplace, were otherwise randomly selected by the Population Register Center. The data on working ability were obtained from the Social Insurance Institution. Patients were divided into 3 groups: SCS trial only, SCS implanted permanently, and SCS implanted but later explanted. RESULTS: A rehabilitation subsidy was given to 68 patients and 8 controls for a mean of 5.2 (95% confidence interval [CI] 2.4-8.2) and 0.2 (95% CI 0.05-0.6) days per month (P < .05). At the end of follow-up, 16 (37%), 13 (33%), 25 (22%), and 27 (5%) subjects were on disability pension (DP) in the SCS trial, SCS explanted, SCS permanent, and control groups. Patients in the SCS trial-only group were significantly more often on DP than were patients with permanent SCS (odds ratio 2.6; 95% CI 1.2-5.9; P = .02) CONCLUSION: Permanent SCS usage was associated with reduced sick leave and DP. Prospective study will be required to assess possible predictive value. KEY WORDS: Disability pension, Failed back surgery syndrome, FBSS, Rehabilitation subsidy, SCS, Sickness allowance, Spinal cord stimulation Neurosurgery 84:1225–1232, 2019 DOI:10.1093/neuros/nyy530 O ne in 5 Europeans (19%) are estimated to suffer from chronic pain.1 Chronic pain is an economic burden, causing many direct and indirect costs.2,3 In 2014 in Finland, backache diseases caused approximately 2 million daily sickness allowance (SA) days, resulting in SA costs of €117.9 million.4 At the end of 2013, nearly 27 000 out of 5.5 million people were retired in Finland due to backache ABBREVIATIONS: CI, confidence interval; DP, disability pension; FBSS, failed back surgery syndrome; ICD, international classification of diseases; IPG, internal pulse generator; NHI, National Health Insurance; OR, odds ratio; PRC, Population Register Center; RS, rehabilitation subsidy; SA, sickness allowance; SCS, spinal cord stimulation; SII, Social Insurance Institution www.neurosurgery-online.com diseases, resulting in €346.6 million in disability pension (DP) costs.5 Neuropathic pain results from a lesion or disease affecting the somatosensory system at either the peripheral or central level.6 The most common neuropathic pain is pain radiating from the lower back to the lower extremities.7 Spinal cord stimulation (SCS) is an effective treatment that can be used for any neuropathic pain, but the most common indication is failed back surgery syndrome (FBSS).8 FBSS is defined as persistent or recurrent pain in the lower back or legs after technically and anatomically successful lumbosacral spine surgeries.9 SCS has been found to be a more effective treatment for FBSS than reoperations are.10,11 A prospective randomized controlled multicenter trial established that patients undergoing SCS had better outcomes at 2-yr follow-up than VOLUME 84 | NUMBER 6 | JUNE 2019 | 1225 Tiina-Mari Ikäheimo, RN‡ KAIJANKOSKI ET AL METHODS Data Collection The medical charts of 230 FBSS patients who received SCS implantation at KUH Neurosurgery between January 1, 1996, and December 31, 2014 were retrospectively evaluated. A neurosurgeon, orthopedic surgeon, or pain physician set a diagnosis of FBSS and provided the primary treatment, such as physical therapy and oral analgesics. Patients suffered from radicular lower limb pain or combined lumbar pain after at least 1 lumbar disc or decompression operation. Untreated depression was a contraindication for SCS. We limited our time for reviewing the ability to work to 4 yr (2 yr before and 2 yr after SCS implantation). During the follow-up period, patients who had reached the age of 63 yr (n = 30; the retirement age in Finland) or who had died (n = 1) were excluded from this study. One patient was excluded due to incomplete data. A matched control cohort was created using the PRC for SCS patients to evaluate the effect of the treatment. With one exception (who received only 1 control), the PRC randomly selected 3 live controls for each patient in the study. The control group was matched by (1) age, (2) gender, and (3) place of birth; in addition, (4) both the patient and the control had to be alive on the index day. The index day for matching was the day of SCS implantation or explantation. The Social Insurance Institution (SII) of Finland is an independent social security institution that runs the National Health Insurance (NHI) scheme. The NHI scheme is part of the Finnish social security system that covers all permanent residents of Finland. The SII of Finland maintains a nationwide registry of all patients who are receiving or have received SA or rehabilitation subsidy (RS, a fixed-term DP), or who are or have been retired. The data for SA, RS, and DP were derived from the register of the SII of Finland. Data included the start and end dates, as well as the International Classification of Diseases (ICD-10) diagnoses of each SA/RS/DP p (...truncated)