Medical Policy: 07.01.63
Original Effective Date: February 2014
Reviewed: January 2019
Revised: January 2019
This policy contains information which is clinical in nature. The policy is not medical advice. The information in this policy is used by Wellmark to make determinations whether medical treatment is covered under the terms of a Wellmark member's health benefit plan. Physicians and other health care providers are responsible for medical advice and treatment. If you have specific health care needs, you should consult an appropriate health care professional. If you would like to request an accessible version of this document, please contact customer service at 800-524-9242.
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This Medical Policy document describes the status of medical technology at the time the document was developed. Since that time, new technology may have emerged or new medical literature may have been published. This Medical Policy will be reviewed regularly and be updated as scientific and medical literature becomes available.
Image-guided minimally invasive spinal decompression is a percutaneous procedure for decompression of the central spinal canal in patients with spinal stenosis and hypertrophy of the ligamentum flavum. Spinal stenosis can occur in the cervical, thoracic, or lumbar regions of the spine. In spinal stenosis the space around the spinal cord narrows, compressing the spinal cord and its nerve roots. Narrowing is most often caused by osteophyte formation, herniated discs or thickented ligaments (ligamentum flavum). Spinal stenosis is often linked to age-related changes in disc height and arthritis of the facet joints. The goal of surgical treatment is to “decompress” the spinal cord and/or nerve roots. Image-guided minimally invasive spinal decompression is proposed as an alternative to existing posterior decompression procedures.
The most common symptoms of cervical/thoracic spinal stenosis are neck pain and radiculopathy of the shoulder and arm. The most common cause of cervical radiculopathy is degenerative changes, including disc herniation. For patients with cervical or thoracic stenosis, surgical treatment includes discectomy or foraminal decompression.
The most common symptoms of lumbar spinal stenosis (LSS) are back pain with neurogenic claudication (i.e. pain, numbness, weakness) in the legs that worsens with standing or walking and is alleviated by sitting or leaning forward. Lumbar spinal stenosis (LSS) is among the most common reasons for back surgery and the most common reason for lumbar spine surgery in adults over the age of 65. For patients with LSS, surgical laminectomy has established benefits in reducing pain and improving quality of life. Posterior decompression (laminectomy) for LSS has been evolving toward increasingly minimally invasive procedures in an attempt to reduce postoperative morbidity and spinal instability.
Image-guided minimally invasive spinal decompression or MILD is usually performed in the lumbar spine. During the image-guided minimally invasive spinal decompression (MILD) procedure, a specialized cannula and surgical tools (mild®) are used under fluroscopic guidance for bone and tissue sculpting near the spinal canal. MILD is indicated for central stenosis only, without the capability of addressing nerve root decompression or disc herniation should either be required.
Percutaneous image-guided minimally invasive lumbar decompression using a specially designed tool kit (mild®) has been proposed as an ultra-minimally invasive treatment of lumbar spinal stenosis (LSS). In this procedure, the epidural space is filled with contrast medium under fluoroscopic guidance. Using a 6-gauge cannula clamped in place with a back plate, single-use tools (portal cannula, surgical guide, bone rongeur, tissue sculpter, trocar) are used to resect thickened ligmentum flavum and small pieces of lamina. The tissue and bone sculpting is conducted entirely under fluoroscopic guidance, with contrast media added throughout the procedure to aid visualization of the decompression. The process is repeated on the opposite side for bilateral decompression of the central canal. The devices are not intended for use near the lateral neural elements and are contraindicated for disc procedures.
The protocol for the MiDAS ENCORE (Evidence-based Neurogenic Claudication Outcomes Research) trial (NCT02093520) was approved by the Centers for Medicare and Medicaid Services under coverage with evidence development. Staats et. al. (2016) reported on this nonblinded, prospective, multi-center, randomized controlled clinical trial, conducted at 26 U.S. interventional pain management centers. This trial compared patient outcomes following treatment with the MILD® procedure (minimally invasive lumbar decompression) (treatment group) or epidural steroid injections (ESIs) (active control group) in lumbar spinal stenosis (LSS) patients with neurogenic claudication and verified ligamentum flavum hypertrophy. Three hundred and two patients were randomized in a 1:1 ratio to MILD (149) or ESIs (153). Six-month follow-up was completed and is presented in this report. In addition, one year follow-up will be conducted for patients in both study arms, and supplementary 2 year outcome data will be collected for patients in the MILD group only. Outcomes assessed used the Oswestry Disability Index (ODI), numeric pain rating scale (NPRS) and Zurich Claudication Questionnaire (ZCQ). Primary efficacy is the proportion of ODI responders, tested for statistical superiority of the MILD group versus the active control group (ESIs). ODI responders are defined as patients achieving the validated Minimal Important Change (MIC) of =10 point improvement in ODI from baseline to follow-up. Similarly, secondary efficacy includes proportion of NPRS and ZCQ responders using validated MIC thresholds. Primary safety is the incidence of device or procedure-related adverse events in each group. At 6 months, all primary and secondary efficacy results provided statistically significant evidence that MILD is superior to the active control. For primary efficacy, the proportion of ODI responders in the MILD group (62.2%) was statistically significantly higher than for the epidural steroid group (35.7%) (P < 0.001). Further, all secondary efficacy parameters demonstrated statistical superiority of MILD versus the active control. The primary safety endpoint was achieved, demonstrating that there is no difference in safety between MILD and ESIs (P = 1.00). Limitations include lack of patient blinding due to considerable differences in treatment protocols, and a potentially higher non-responder rate for both groups versus standard-of-care due to study restrictions on adjunctive pain therapies.
Benyamin et. al. (2016), reported on the safety and efficacy results at one year follow up of the MiDAS ENCORE randomized controlled trial (see above). Outcomes at 2 years will be collected and reported for patients in the minimally invasive lumbar decompression (MILD) group only. At 1-year follow-up, Oswestry Disability Index (ODI), numeric pain rating scale (NPRS), and all 3 Zurich Claudication Questionnaire (ZCQ ) domains (Symptom Severity, Physical Function and Patient Satisfaction) demonstrated statistically significant superiority of MILD versus the active control (epidural steroid injections [ESIs]). For primary efficacy, the 58.0% ODI responder rate in the MILD group was higher than the 27.1% responder rate in the epidural steroid group (P < 0.001). The primary safety endpoint was achieved, demonstrating that there is no difference in safety between MILD and ESIs (P = 1.00). There was a lack of patient blinding due to considerable differences in treatment protocols, and a potentially higher non-responder rate for both groups versus standard-of-care due to adjunctive pain therapy study restrictions. Study enrollment was not limited to patients that had never received ESI therapy. The authors concluded, one-year results of this randomized controlled clinical trial (RCT) demonstrated that MILD is statistically superior to ESIs in the treatment of LSS (lumbar spinal stenosis) patients with neurogenic claudication and verified central stenosis due to ligamentum flavum hypertrophy. Primary and secondary efficacy outcome measures achieved statistical superiority in the MILD group compared to the control group (ESIs). With 95% of patients in this study presenting with 5 or more LSS co-factors, it is important to note that patients with spinal co-morbidities also experienced statistically significant improved function that was durable through 1 year.
Staats et. al. (2018) reported on the 2 year follow-up for the MILD (minimally invasive lumbar decompression) study patients of the MiDAS ENCORE trial. This prospective, multicenter, randomized controlled clinical study compared outcomes for patients treated with MILD versus patients treated with epidural steroid injections . Follow-up occurred at 6 months and at 1 year for the randomized phase and at 2 years for MILD subjects only. Oswestry Disability Index (ODI), Numeric Pain Rating Scale (NPRS), and Zurich Claudication Questionnaire (ZCQ) were used to evaluate function and pain. Safety was evaluated by assessing incidence of device/procedure-related adverse events. All outcome measures demonstrated clinically meaningful and statistically significant improvement from baseline through 6-month, 1-year, and 2-year follow-ups. At 2 years, Oswestry Disability Index (ODI) improved by 22.7 points, Numeric Pain Rating Scale (NPRS) improved by 3.6 points, and Zurich Claudication Questionnaire (ZCQ) symptom severity and physical function domains improved by 1.0 and 0.8 points, respectively. There were no serious device/procedure-related adverse events, and 1.3% experienced a device/procedure-related adverse event. The authors concluded, MILD showed excellent long-term durability, and there was no evidence of spinal instability through 2-year follow-up.
In 2009, a systematic review by Chou et. al. assessed benefits and harms of surgery for nonradicular back pain with common degenerative changes, radiculopathy with herniated lumbar disc, and symptomatic spinal stenosis and it was commissioned by the American Pain Society. Although back surgery rates continue to increase, there is uncertainty or controversy about utility of back surgery for various conditions. Electronic database searches on Ovid MEDLINE and the Cochrane databases were conducted through July 2008 to identify randomized controlled trials and systematic reviews of the above therapies. All relevant studies were methodologically assessed by 2 independent reviewers using criteria developed by the Cochrane Back Review Group (for trials) and Oxman (for systematic reviews). A qualitative synthesis of results was performed using methods adapted from the US Preventive Services Task Force. For nonradicular low back pain with common degenerative changes, they found fair evidence that fusion is no better than intensive rehabilitation with a cognitive-behavioral emphasis for improvement in pain or function, but slightly to moderately superior to standard (nonintensive) nonsurgical therapy. Less than half of patients experience optimal outcomes (defined as no more than sporadic pain, slight restriction of function, and occasional analgesics) following fusion. Clinical benefits of instrumented versus noninstrumented fusion are unclear. For radiculopathy with herniated lumbar disc, they found good evidence that standard open discectomy and microdiscectomy are moderately superior to nonsurgical therapy for improvement in pain and function through 2 to 3 months. For symptomatic spinal stenosis with or without degenerative spondylolisthesis, they found good evidence that decompressive surgery is moderately superior to nonsurgical therapy through 1 to 2 years. For both conditions, patients on average experience improvement either with or without surgery, and benefits associated with surgery decrease with long-term follow-up in some trials.
In 2014, Kreiner et. al. completed an evidence based review of the available data to determine if the literature supports the use of minimally invasive lumbar decompression (mild®) procedure (Vertos Medical, Aliso Viejo, CA, USA) to reduce pain and improve function in patients with symptomatic degenerative lumbar spinal stenosis. Studies were identified from PubMed, Embase, and the Cochrane Library. Articles were evaluated using the Grading of Recommendations Assessment, Development and Evaluation Working Group system. Results were compiled assessing short- (4-6 weeks), medium- (3-6 months), and long-term (>1 year) outcomes. The primary outcomes evaluated were pain, measured by the visual analog scale (VAS), and function, measured by the Oswestry Disability Index (ODI). Secondary outcomes included pain and patient satisfaction, measured by the Zurich Claudication Questionnaire, adverse effects/complications, and changes in utilization of co-interventions. The literature search revealed one randomized controlled trial (RCT) and 12 other studies (seven prospective cohort, four retrospective, and one case series) that provided information on the use of mild® in patients with degenerative lumbar spinal stenosis. All studies showed statistically significant improvements in VAS and ODI scores at all time frames compared with pre-procedure levels; the RCT showed improvement over controls. Categorical data were not provided; thus, the proportion of patients who experienced minimal clinically meaningful outcomes is unknown. The authors concluded, the current body of evidence addressing mild® is of low quality. High-quality studies that are independent of industry funding and provide categorical data are needed to clarify the proportions of patients who benefit from mild® and the degree to which these patients benefit. Additional data at up to 2 years are needed to determine the overall utility of the procedure.
One potential indication for minimally invasive lumbar decompression (MILD) is patients with symptomatic LSS primarily caused by a hypertrophic ligamentum flavum who are considered poor candidates for traditional decompressive surgery.
In 2010, Lingreen et. al. examined the post-procedure patient course following minimally invasive lumbar decompression (MILD) in a retrospective evaluation. They examined the minor adverse events and periprocedural course associated with MILD. Additionally, evaluated the efficacy of the procedure with regard to pain relief and functional status. Forty-two patients meeting magnetic resonance imaging (MRI) criteria for MILD underwent the procedure performed by 2 interventional pain management physicians working at the same center. Most patients had not been considered surgical candidates by a spine surgeon. The pre and post procedure visual analog scale (VAS) as well as markers of global function were recorded. Major and minor adverse events were tracked and patient outcomes reported. There were no major adverse events reported. Of the minor adverse events, soreness lasting 3.8 days was most frequently reported. No patients required overnight observation and only 5 required postoperative opioid analgesics. Patients self-reported improvement in function as assessed by ability to stand and ambulate for greater than 15 minutes, whereas prior to the procedure 98% reported significant limitations in these markers of global functioning. Visual analog pain scores were significantly decreased by 40% from baseline. Eighty-six percent of the patients reported that they would recommend the MILD procedure to others.
In 2011, Chopko reported on minimally invasive lumbar decompression (MILD) using image guided fluoroscopy in 14 patients considered at high risk for complications from open spine surgery and general anesthesia. Prospectively collected visual analog scale (VAS) and Oswestry Disability Index (ODI) data analyzed at the most recent follow-up. The average follow-up duration was 23.5 weeks. A statistically significant improvement in VAS scores was observed, with a reduction in pain of 53% compared with preoperative levels. In contrast, the ODI scores failed to improve.
The evidence on image-guided minimally invasive lumbar decompression (IG-MILD) to treat lumbar stenosis consists of a randomized controlled trial (RCT), a systematic review and a number of prospective and retrospective cohort studies and case series. The RCT compared MILD (minimally invasive lumbar decompression) with epidural steroid injections (ESIs) (control) in patients with ligamentum flavum hypertrophy and who failed conservative therapy. Follow-up of both groups (MILD and ESIs) was through one year, and the two year follow up was only for the MILD group. Results have suggested reductions in pain and improvements in function scores in the MILD group versus the control group (epidural steroid injections). This trial was unblinded and there is evidence of differing expectations and follow-up in both groups, suggesting a high-risk of bias. No studies were found comparing MILD to open decompression. The available evidence is insufficient to determine the efficacy of image-guided minimally invasive lumbar decompression compared with placebo (control) or to determine the efficacy of image-guided minimally invasive lumbar decompression compared with open decompression. In addition, the complication rates and reoperation rates for this procedure compared with those of decompression surgery is unknown. Trials with relevant control groups could provide greater certainty on the risk and benefits of this procedure.
No evidence assessing use of image-guided minimally invasive cervical or thoracic decompression for treatment of patients with cervical or thoracic spinal stenosis was found.
There is no evidence to inform conclusions about the use of image-guided minimally invasive cervical or thoracic decompression to treat cervical or thoracic spinal stenosis. The evidence is insufficient to determine the effects of the technology on net health outcomes. Randomized controlled clinical trials are needed to assess the clinical evidence to determine whether this technology improves the net health outcome.
No guidelines or position statements were identified.
The mild® tool kit (Vertos Medical Inc., San Jose, CA) initially received 510(k) marketing clearance as the X-Sten MILD Tool Kit (X-Sten Corp.) from the US Food and Drug Administration (FDA) on December 19, 2006, as a class II device with intended use as a set of specialized surgical instruments to be used to perform percutaneous lumbar decompressive procedures for the treatment of various spinal conditions. A subsequent approval for the Vertos Medical mild® Device Kit (Vertos Medical Inc.) was given by the FDA on February 4, 2010.
Vertos mild® instructions for use state that the devices are not intended for disc procedures but rather for tissue resection at the perilaminar space, within the interlaminar space, and at the ventral aspect of the lamina. These devices are not intended for use near the lateral neural elements and remain dorsal to the dura using image guidance and anatomical landmarks.
See related medical policy 07.01.39 Miscellaneous Surgical Treatment of Back Pain
Image-guided minimally invasive decompression for the treatment of spinal stenosis is considered investigational due to the lack of clinical evidence demonstrating an impact on improved health outcomes.
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