Risk Factors Associated with Spinal Cord Stimulation Failure in Patients with Chronic Pain: A Single-Center Retrospective Cohort Study

Background/Objectives: Spinal cord stimulation (SCS) can provide long-term relief for selected patients with refractory chronic pain, but treatment failure may occur without device explantation. This study examined patient-, clinical-, and device-related factors associated with SCS failure after permanent implantation. Methods: This retrospective, single-center cohort study included 108 adults who underwent permanent SCS implantation at the Centre Hospitalier de l’Université de Montréal between 2007 and 2022. Failure was defined as completed or planned explantation, inadequate pain relief accompanied by a desire or plan for removal, or documented device non-use. Associations were evaluated using univariable categorical tests. Paired pain intensity and morphine milligram equivalent (MME) doses were compared using Wilcoxon signed-rank tests. Results: At the most recent documented assessment, composite SCS failure occurred in 40/108 patients (37.0%), and completed explantation occurred in 25/108 (23.1%); these proportions were not adjusted for unequal follow-up duration. The leading reasons for explantation were loss of efficacy (36.0%), paresthesia or dysesthesia (28.0%), and patient request (24.0%). In exploratory univariable analysis, smoking was associated with documented failure (RR = 1.70, 95% CI 1.05–2.75; p = 0.032). Failure differed across comorbidity-count categories (Cramér’s V = 0.34, 95% CI 0.00–0.48; p = 0.019), although the pattern was nonmonotonic. Neither association remained statistically significant after Benjamini–Hochberg correction across 26 comparisons (both q = 0.416). Sex, psychiatric history, pain duration, implantation approach, generator type, and generator location were not significantly associated with failure. The median within-patient reduction in pain intensity was 2.50 points (IQR, 1.00–5.00; p < 0.001), whereas the median paired MME change was 0 MME/day (IQR, −60 to 40; p = 0.649). Conclusions: A composite outcome identified a higher prevalence of clinically unsuccessful SCS treatment than completed explantation alone. Smoking showed an unadjusted association with documented failure; however, this finding may reflect confounding or chance arising from multiple comparisons and should be considered hypothesis-generating. Pain intensity improved without a corresponding significant reduction in opioid exposure. These findings require confirmation through prospective, prespecified multivariable and time-to-event analyses.