Lam, Christopher

Background The efficacy of EVOKE therapy, a closed-loop spinal cord stimulation (SCS) system, has been demonstrated in a double-blinded randomized controlled trial (RCT). RCT evidence, however, may not be generalizable to clinical practice, while limitations of real-world evidence may affect its validity. The aim of this study was to evaluate the effectiveness of EVOKE therapy in routine clinical practice employing a rigorous data collection approach. Methods The ECAP study was a prospective, multicenter, single-arm, pragmatic study that enrolled SCS candidates with chronic, intractable trunk and/or limb pain in 22 US investigational sites. PROMIS-29 questionnaire and objective neurophysiological metrics were collected, and minimal clinically important differences (MCIDs) were used to characterize baseline dysfunction and response to EVOKE therapy both at trial end and maximal analgesic effect post-implant visit. Pre-specified subgroup analyses were conducted based on diagnosis. Results EVOKE therapy observed included a dose ratio of 1.3 and neural dose accuracy of 2.8 μV. Improvements of >1 MCID were observed for all domains and improvements of ≥2 MCIDs were observed for six of the seven domains. Improvements observed at trial end were maintained or improved at post-implant visit, with statistically significant improvement in holistic MCID (MD 0.2, 95% CI 0.1 to 0.4, p=0.004), and a significantly greater proportion of patients considered holistic MCID responders (p=0.047). Subgroup analysis by diagnosis showed similar outcomes. Conclusions EVOKE therapy was associated with clinically meaningful improvements in a real-world chronic pain population across different subgroups and disease pathologies, with effects observed at trial end reproduced at post-implant visit.

AbstractBackgroundLumbar medial branch nerve radiofrequency ablation (LRFA) is an interventional procedure used to treat chronic lumbar facet joint pain. Because the medial branch nerves also innervate the multifidus muscle, it has been proposed that LRFA may pose a risk of multifidus atrophy and/or dysfunction. However, the quality and level of evidence to answer this clinical question have not been established. Therefore, this review aimed to systematically appraise the literature to discern whether the prevailing evidence substantiates the hypothesis in question.MethodsA systematic review compliant with the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses guidelines was performed to evaluate the quality and level of evidence of studies reporting functional and/or structural changes in the multifidus muscle following LRFA.ResultsOnly five cohort studies met inclusion criteria. Two studies assessed changes in multifidus function following LRFA with confirmed denervation at electromyography and significant reduction in multifidus shear modulus with ultrasound shear wave elastography. Of the four studies that evaluated changes in multifidus structure with magnetic resonance imaging following LRFA, two demonstrated a decrease in cross‐sectional area or an increase in fat infiltration, one demonstrated no change, and one revealed an apparent increase. Given the destructive nature attributed to LRFA, some degree of multifidus atrophy and/or dysfunction may be plausible, albeit with a very low certainty that relies on a restricted body of literature of modest quality and with a presence of high bias.ConclusionThere is a paucity of studies discussing the potential association between LRFA and multifidus atrophy and/or dysfunction. In light of the shortage of high‐quality studies and the absence of standardized protocols to assess both changes in the structure and function of the multifidus subsequent to LRFA, there is a pressing need for more prospective studies with a high methodological rigor to comprehensively address and answer this enduring debate in clinical practice.

Abstract Objectives Lumbar spine surgery is a common procedure for treating disabling spine‐related pain. In recent decades, both the number and cost of spine surgeries have increased despite technological advances and modification in surgical technique. For those patients that have continued uncontrolled back and/or lower extremity pain following lumbar spine surgery, spinal cord stimulation (SCS) has emerged as a viable treatment option. However, the impact of lumbar spine surgical history remains largely unstudied. Specifically, the current study considers the impact of number of prior lumbar spine surgeries on pain relief outcomes following SCS implantation. Materials and Methods We queried the electronic medical record of five separate pain practices for all patients who have undergone a SCS implant between January 1, 2017, and March 1, 2020. Inclusion criteria consisted of any patients with an SCS implant who underwent a prior lumbar spine surgery. The primary outcome was the mean calculated percentage pain relief in patients based on number of prior lumbar spine surgeries. Results There was a total of 1974 total SCS implant cases identified across five separate pain clinics. There was no difference in mean calculated pain relief in patients with one prior spine surgery versus those with two or more prior spine surgeries (28.2% vs. 25.8%, adjusted β‐coefficient –3.1, 95% CI –8.9 to 2.7, p = 0.290). Similarly, when analyzing number of spine surgeries as a continuous variable, there was no association between number of spine surgeries and calculated pain relief (adjusted β‐coefficient –1.5, 95% CI –4.0 to 1.1, p = 0.257). Additionally, after patients were stratified based on waveform, there was no association between number of prior lumbar spine surgeries (analyzed both as a categorical and continuous variable) and calculated percentage pain relief. Conclusions This multicentered retrospective study found that there was no significant difference in pain scores in individuals who received SCS following one or more lumbar spine surgeries. Additionally, the waveform of the SCS device had no statistically significant impact on post‐operative pain scores following one or more lumbar spine surgeries.