According to a study published in Neuromodulation, five years after implantation, spinal cord stimulators have been explanted in 13.5% of patients. Furthermore, about 10% of these explants are for non-infections reasons. Predictors of non-infected explants include being younger, using tobacco, and having certain psychiatric conditions.
Mark C Dougherty (Department of Neurosurgery, University of Iowa Hospitals and Clinics, Iowa City, USA) and colleagues report that therapeutic failure for spinal cord stimulator “remains remarkably common”. As a consequence of this failure, the authors add, “a substantial number of have their devices removed, or explanted”.
The lack of data in this area prompted Dougherty et al to “perform survival analysis and multivariate regression analysis to describe timing and predictors of spinal cord stimulator removal”. “We hypothesised that certain baseline patient characteristics would be able to predict risk of future device removal. We further hypothesised that, although most explants would happen within one to two years of implantation, removals would continue to occur years later,” they comment.
Using a private insurance database, the authors identified 252 patients who undergone spinal cord stimulation implantation. Of these, within the available follow-up time (mean 2.6 years), 17 patients (6.7%) underwent explantation with 11 (4.4%) undergoing explantation for non-infectious reasons. In a Kaplan-Meier analysis, excluding the patients who underwent explantation for a non-infectious reason, Dougherty et al predicted “an explantation rate of approximately 10% at five years after implantation for non-infectious reasons”. The rate increased to 13.5% if infected explants were included in the analysis.
A multivariate analysis of the potential predictors of explant indicated that age, tobacco use, and “other mental health disorders” were all significant factors. However, the authors note that “other mental health disorders” are “difficult to define precisely” and, therefore, explored the factor in more detail. “Eight of the 11 [non-infected] explant patients had a diagnosis corresponding to ‘other’ mental health disorders. In all but one patient, the diagnosis was either 1) adjustment disorder with depressive and/or anxiety symptoms or 2) pain disorder with related psychological factors. The last patient had a personality disorder,” Dougherty et al comment.
The investigators write that although the current study is neither the largest insurance data base study on spinal cord stimulation explantation, nor the first survival analysis for the modality’s explanation, it represents the first study combining these approaches. They also acknowledge the importance of distinguishing between explants that were done for infection, and those carried out for other reasons, such as device failure or patient satisfaction, as “device infection does not necessarily suggest a lack of device efficacy”.
Concluding their research, Dougherty and the team state that spinal cord stimulator removal is less likely to occur in “older non-smokers without certain psychiatric disorders”. “Ultimately, while spinal cord stimulation is helpful for many patients, there is still much room for improvement in the treatment of refractory chronic pain of the spine and limb,” they add.
Speaking to NeuroNews, Dougherty says: “While certain patient characteristics seem to suggest a higher likelihood of failure and explantation down the road, we are not yet at a point where we can predict these outcomes with enough accuracy to determine—prior to surgery—whether a patient will benefit or not.
“Hopefully, at some point in the future, we will have sufficiently accurate predictive tools, meaning that we can avoid placing spinal cord stimulators that will not be beneficial, thus avoiding pointless surgeries. We also still need better ways to treat chronic pain in patients that do not benefit from spinal cord stimulation.”