High-Frequency Spinal Cord Stimulation for Chronic Pain: Pre-Clinical Overview and Systematic Review of Controlled Trials.

OBJECTIVE: To assess the evidence base for high-frequency spinal cord stimulation (HFSCS). HFSCS has the potential to provide paresthesia-free pain relief for patients with chronic pain, in contrast to conventional spinal cord stimulation, which produces distracting and potentially unpleasant paresthesias. DESIGN: A systematic review following standard methodological guidelines (Prospero #CRD42015029215). METHODS: We searched PubMed to March 14, 2016 without language restriction and hand-checked reference lists. Two authors independently performed study selection, bias evaluations, and data extraction. The pre-clinical review selected studies focusing on the mechanism and non-human experience with HFSCS. Clinically, any prospective study of adults using HFSCS (≥ 1000 Hz) was included. RESULTS: Pre-clinical studies have characterized many aspects underlying the mechanism of HFSCS. For the clinical systematic review, eight trials (236 participants randomized or 160 followed prospectively) met inclusion criteria. All trials of HFSCS focused on patients with chronic low back pain with one exception, which included patients with chronic migraine. All but one trial documented funding by industry. Performance bias due to unmasked participants, physicians, and outcome assessors limited the quality of all but one study. CONCLUSIONS: Significant growth in the preclinical and clinical evidence base for HFSCS suggests that HFSCS may differ from conventional SCS in mechanism of action and efficacy of treatment, respectively. Addressing current knowledge gaps in clinical evidence will require standardization in trial reporting and leveraging the paresthesia-free characteristic of HFSCS to enable masking in high-quality randomized controlled trials.

Loss of Efficacy to Spinal Cord Stimulator Therapy: Clinical Evidence and Possible Causes.

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.

Epidemiology of nonfatal bicycle injuries presenting to United States emergency departments, 2001-2008.

OBJECTIVES: The purpose of this study was to describe the epidemiology of bicycle-related injuries presenting to United States emergency departments (EDs). METHODS: The National Electronic Injury Surveillance System All Injury Program (NEISS-AIP) database was used to derive national, weighted estimates of nonfatal ED visits for bicycle-related injuries by patient age, sex, diagnosis, injured body part, locale of incident, traffic-relatedness of incident, and month of incident. RESULTS: Males accounted for 73% of all bicycle-related injury ED visits. Patients aged 10 to 14 years represented the 5-year age interval with the highest rate of bicycle injury visits (488 per 10,000). Fifty-six percent of ED visits for bicycle-related injuries came from cyclists who were riding on the street, with increased street ridership in those who were older than 15 years, and 99.7% of all patient injuries occurring on the street (as opposed to other locations) were related to motor vehicle collisions (MVCs). The head and face were the most injured body parts in the overall population. In addition, the largest proportion of head injuries, relative to total injuries in the age group, occurred in the very young (0 to 4 years) and elderly (65+ years) populations. The leading rider injury diagnoses were contusion, abrasions, and hematomas. The incidence of bicycle-related injuries peaked in the month of July. CONCLUSIONS: The study identified the characteristics of bicycle-related injuries across various age groups of riders. This information will aid in developing more effective age-appropriate injury prevention strategies. The frequency of MVC-related injuries deserves attention and suggests the need to examine strategies for limiting interactions between moving vehicles and bicyclists.