MiDAS ENCORE: Randomized Controlled Study Design and Protocol

Abstract

Background: Epidural steroid injections (ESIs) are commonly used for treatment of symptomatic lumbar spinal stenosis (LSS). ESIs are generally administered after failure of conservative therapy. For LSS patients suffering from neurogenic claudication, the mild® procedure provides an alternative to ESIs via minimally invasive lumbar decompression. Both ESIs and mild offer interventional pain treatment options for LSS patients experiencing neurogenic claudication refractory to more conservative therapies.

Study design: Prospective, multi-center, randomized controlled, clinical study.

Setting: Twenty-six interventional pain management centers throughout the United States.

Objective: To compare patient outcomes following treatment with either mild or ESIs in LSS patients with neurogenic claudication and having verified ligamentum flavum hypertrophy.

Methods: Study participants include Medicare beneficiaries who meet study inclusion/exclusion criteria. Eligible patients will be randomized in a 1:1 ratio to one of 2 treatment arms, mild (treatment group) or ESI (control group). Each study group will include approximately 150 patients who have experienced neurogenic claudication symptoms for ≥ 3 months duration who have failed to respond to physical therapy, home exercise programs, and oral analgesics. Those randomized to mild are prohibited from receiving lumbar ESIs during the study period, while those randomized to ESI may receive ESIs up to 4 times per year. Patient assessments will occur at baseline, 6 months, and one year. An additional assessment will be conducted for the mild patient group at 2 years.

Outcome measures: The primary efficacy outcome measure is the proportion of Oswestry Disability Index (ODI) responders from baseline to one year follow-up in the treatment group (mild) versus the control group (ESI). ODI responders are defined as those patients achieving the validated Minimal Important Change (MIC) of ≥ 10 point improvement in ODI from baseline to follow-up as a clinically significant efficacy threshold. Secondary efficacy outcome measures include the proportion of Zurich Claudication Questionnaire (ZCQ) and Numeric Pain Rating Scale (NPRS) responders from baseline to follow-up using validated MIC thresholds. Improvement in ZCQ domains of ≥ 0.5 is considered significant, and a Patient Satisfaction score of at least 2.5 represents a satisfied patient. A reduction of ≥ 2 points in NPRS is considered significant pain relief. The primary safety outcome measure is the incidence of device- and/or procedure-related adverse events.

Results: Descriptive summaries will be presented by randomized group for all outcome measures at baseline and follow-up time points. Inferential statistical analysis will be conducted to determine significant differences related to functional improvement, pain relief, and safety outcomes. Primary study results will be presented based on one-year follow-up data, with an interim analysis report when 6-month follow-up data become available.

Limitations: Patients are not blinded due to significant differences in treatment protocols between study groups. Also, since neither study arm is focused on treatment of radicular pain, there may be a higher non-responder rate for both groups versus standard of care due to study restrictions on adjunctive pain therapies.

Conclusions: This prospective, multi-center, randomized controlled study will provide Level I evidence of the safety and effectiveness of mild versus ESIs in managing neurogenic claudication symptoms in LSS patients.