Aiudi, Christopher M.

Background: Although spinal cord stimulation (SCS) therapy has been shown to be efficacious in various pain conditions, the ability for SCS therapy to maintain long-term efficacy has been questioned. Objective: The purpose of this study was to investigate whether a loss of efficacy (LOE) phenomenon exists with SCS therapy and to investigate if this phenomenon is more apparent in any specific patient population. Study Design: A retrospective, observation chart review was conducted to evaluate the patient response to SCS therapy over time. Setting: Massachusetts General Hospital, Boston, Massachusetts. Methods: Patients who received a SCS at the Massachusetts General Hospital, between January 1, 2002 and December 31, 2012, were invited to participate. A total of 62 patients were included in this study. Various models were created to analyze pain score changes over time using 2-tailed statistical analysis. Additionally, one-way ANOVA and Pearson’s chi-square tests were used to determine if certain patient characteristics were associated with LOE. Results: Compared to the visual analog scale (VAS) score at one month after device implantation, pain scores increased 1.95 points after 2 years (95% CI: 1.06 to 2.84, P = < 0.001). There were no significant differences in baseline characteristics between the groups of patients who did and did not lose efficacy of their therapy. However, those who experienced LOE had a baseline SCS therapy VAS score 3.09 points lower than those who did not (95% CI: 1.69 to 4.48, P = < 0.001). Limitations: This study had several limitations including the retrospective nature of its design, confounders to VAS scores, small sample size, missing data points, and the evaluation of only conventional, low-frequency SCS therapy. Conclusions: Patients who received a SCS had a significant increase in VAS scores over time. Our data did not show any baseline patient characteristic that helped predict LOE. However, patients who have significant baseline response to therapy may be more likely to experience LOE. Key words: Spinal cord stimulation, chronic pain, retrospective study, low frequency electrical stimulation, efficacy, chronic pain therapy

AbstractObjectivesSpinal cord stimulation (SCS) therapies are used in the management of patients with complex regional pain syndrome I (CRPS I) and failed back surgery syndrome (FBSS). The purpose of this study was to investigate the racial and health insurance inequalities with SCS therapy in patients with chronic pain who had CRPS I and FBSS.MethodsPatients with chronic pain who had a discharge diagnosis of FBSS and CRPS I were identified using the National Inpatient Sample database. Our primary outcome was defined as the history of SCS utilization by race/ethnicity, income quartile, and insurance status. Multivariable logistic regression was used to determine the variables associated with utilization of SCS therapy.ResultsBetween 2011 and 2015, 40,858 patients who were hospitalized with a primary diagnosis of FBSS and/or CRPS I were identified. Of these patients, 1,082 (2.7%) had a history of SCS therapy. Multivariable regression analysis revealed that compared to White patients, Black and Hispanic patients had higher odds of having SCS therapy (Black patients: odds ratio [OR] = 1.41; 95% confidence interval [CI], 1.12 to 1.77; P = 0.003; Hispanic patients: OR = 1.41; 95% CI, 1.10 to 1.81; P = 0.007). Patients with private insurance had significantly higher odds of having SCS therapy compared with those with Medicare (OR = 1.24; 95% CI, 1.08 to 1.43; P = 0.003). Compared to patients with Medicare, Medicaid patients had lower odds of having SCS therapy (OR = 0.50; 95% CI, 0.36 to 0.70; P < 0.001).ConclusionsOur study suggests that socioeconomic disparities may exist in the utilization of SCS among hospitalized patients with CRPS I and FBSS the United States. However, confirming these data from other administrative databases, in the outpatient setting, may shed more insight.