MiDAS I (mild® Decompression Alternative to Open Surgery): A Preliminary Report of a Prospective, Multi-Center Clinical Study

Abstract

ackground: Neurogenic claudication due to lumbar spinal stenosis is a common problem that can be caused by many factors including hypertrophic ligamentum flavum, facet hypertrophy, and disc protrusion. When standard medical therapies such as pain medication, epidural steroid injections, and physical therapy fail, or when the patient is unwilling, unable, or not severe enough to advance to more invasive surgical procedures, both physicians and patients are often left with a treatment dilemma. Patients in this study were treated with mild®, an ultra-minimally invasive lumbar decompression procedure using a dorsal approach. The mild procedure is performed under fluoroscopic imaging to resect bone adjacent to, and achieve partial resection of, the hypertrophic ligamentum flavum with minimal disruption of surrounding muscular and skeletal structure. Objective: To assess the clinical application and patient safety and functional outcomes of the mild lumbar decompression procedure in the treatment of symptomatic central canal spinal stenosis. Study Design: Multi-center, non-blinded, prospective clinical study. Setting: Fourteen US spine specialist practices. Methods: Between July 2008 and January 2010, 78 patients were enrolled in the MiDAS I Study and treated with the mild procedure for lumbar decompression. Of these patients, 6-week follow-up was available for 75 patients. Outcome Assessment: Visual Analog Score (VAS), Oswestry Disability Index (ODI), Zurich Claudication Questionnaire (ZCQ), and SF-12v2® Health Survey. Outcomes were assessed at baseline and 6 weeks post-treatment. Results: There were no major device or procedure-related complications reported in this patient cohort. At 6 weeks, the MiDAS I Study showed statistically and clinically significant reduction of pain as measured by VAS, ZCQ, and SF-12v2. In addition, improvement in physical function and mobility as measured by ODI, ZCQ, and SF-12v2 was statistically and clinically significant in this study. Limitations: This is a preliminary report encompassing 6-week follow-up. There was no control group. Conclusions: In this 75-patient series, and in keeping with a previously published 90-patient safety cohort, the mild procedure proved to be safe. Further, based on near-term follow-up, the mild procedure demonstrated efficacy in improving mobility and reducing pain associated with lumbar spinal canal stenosis. Key words: Spine, lumbar, decompression, fluoroscopy, mild, stenosis, ligamentum flavum, minimally invasive