MILD® Procedure for Lumbar Spinal Stenosis - Now Available in Canada
Health Canada has approved the MILD® (Minimally Invasive Lumbar Decompression) procedure for lumbar spinal stenosis caused by ligamentum flavum hypertrophy. Canadians now have access to a percutaneous, image-guided treatment that has been available in the United States since 2010 — backed by over a decade of clinical evidence.
What is lumbar spinal stenosis?
Lumbar spinal stenosis (LSS) is a narrowing of the spinal canal in the lower back that places pressure on the spinal cord and nerve roots. It is one of the most common causes of chronic low back and leg pain in adults over 60, and among the most frequent reasons for spinal surgery in older Canadians.
The narrowing has several causes — bone overgrowth, bulging discs, facet joint enlargement — but a particularly important one is hypertrophy of the ligamentum flavum, the ligament that lines the back wall of the spinal canal. As this ligament thickens with age, it buckles inward and compresses the dural sac and nerve roots behind it.
The resulting symptom pattern is neurogenic claudication: pain, heaviness, cramping, numbness, or tingling in the buttocks, thighs, and legs that worsens with standing and walking, and relieves with sitting or forward bending. Many patients describe being able to walk only short distances before needing to stop and rest.
What is the MILD® procedure?
MILD® — Minimally Invasive Lumbar Decompression — is a percutaneous, fluoroscopically guided outpatient procedure that addresses ligamentum flavum hypertrophy as a direct mechanical cause of spinal canal narrowing. Developed by Vertos Medical (now part of Stryker Interventional Spine), it has been FDA-cleared since 2006 and in broad US clinical use since 2010.
Rather than treating symptoms indirectly, MILD® removes a portion of the thickened ligamentum flavum — and, where needed, a small amount of overlying bone — to physically restore space in the canal. No implants are placed and no general anesthesia is required.
How the procedure is performed
- Pre-operative MRI review
Lumbar MRI is reviewed to confirm ligamentum flavum hypertrophy as a primary source of stenosis at one or more levels, and to plan the approach.
- Positioning and conscious sedation
Patient lies on stomach. The procedure is performed under intravenous sedation and general anesthesia is rarely required.
- Percutaneous portal (~6 mm)
A small portal is created through the skin and soft tissues using dilators. No open incision, no muscle retraction.
- Tissue removal under image guidance
Specialized instruments are advanced under continuous fluoroscopic (X-ray) visualization to remove the hypertrophied ligament and a small portion of bone, widening the canal at target levels.
- Same-day discharge
No sutures are required. Patients are observed briefly and go home the same day. Walking is encouraged within days, followed by a structured rehabilitation program.
Who may be a candidate?
The MILD® procedure is not appropriate for all forms of lumbar spinal stenosis. Careful selection — based on MRI findings, symptom pattern, and prior treatment history — is essential. The following is a general guide; individual clinical assessment is always required.
Features suggesting candidacy
Symptom pattern
Neurogenic claudication — leg and/or buttock pain, heaviness, or cramping that worsens with walking or standing and relieves with sitting or forward flexion.
MRI findings
One or two levels with moderate-severe central spinal canal narrowing due to the hypertrophy of the ligament (ligamentum flavum)
Conservative treatment failure
Inadequate or unsustained relief from physical therapy, anti-inflammatory medications, and/or epidural steroid injections.
High surgical risk or preference
Situations when a more aggressive surgical approach is not desirable or contraindicated.
Situations where MILD® is generally not appropriate
Primary disc pathology
When pain arises predominantly from disc herniation and inflammatory radiculopathy rather than mechanical canal narrowing, other approaches are more suitable.
Significant spinal instability
Grade II or higher spondylolisthesis at the target level generally requires surgical stabilization rather than decompression alone.
Prior surgery at same level
Previous laminectomy or fusion at the intended treatment level may preclude safe percutaneous access.
Predominantly foraminal stenosis
When compression is primarily lateral or foraminal without significant ligamentum flavum contribution, the procedure's mechanism of action is less applicable.
Clinical Evidence
MILD® is supported by two randomized controlled trials and more than a dozen additional controlled prospective studies. The pivotal trial, MiDAS ENCORE, compared mild® against epidural steroid injections in patients with neurogenic claudication and confirmed ligamentum flavum hypertrophy — demonstrating superior outcomes at two years.
| STUDY / SOURCE | KEY FINDING |
|---|---|
| MiDAS ENCORE RCT (2018 | Superior to epidural steroid injections at 2 years for pain, function, and walking capacity in patients with neurogenic claudication and ligamentum flavum hypertrophy |
| Pooled clinical study data | Approximately 85% of patients achieve meaningful improvement in pain and physical function |
| Long-term follow-up (Cleveland Clinic) | Sustained functional improvement in standing tolerance and walking distance at extended follow-up; no major device-related complications |
| Safety profile | Major complication rates equivalent to epidural steroid injections across all clinical studies |
| MIST Consensus Guidelines Deer et al., Pain Practice 2019 | Recommended as the first interventional procedure after conservative care failure in patients with neurogenic claudication and confirmed ligamentum flavum hypertrophy |
Notably, MILD® does not alter the structural integrity of the spine. No hardware is implanted, spinal mechanics are preserved, and no future surgical options are foreclosed.
How does MILD® compare to other treatments?
| MILD® | OPEN DECOMPRESSION / LAMINECTOMY | |
|---|---|---|
| Setting | Outpatient, same-day discharge | Inpatient, hospital stay required |
| Anesthesia | Conscious sedation only | General or spinal anesthesia |
| Incision | ~6 mm portal, no sutures | Open incision, muscle retraction |
| Implants | None | Sometimes (fusion hardware) |
| Recovery | Walking within days | Weeks to months |
| Spinal integrity | Fully preserved | Structurally altered |
| Future surgery | All options remain open | May limit future options |
When compared to epidural steroid injections, MILD® addresses the mechanical cause of stenosis rather than its inflammatory component. Neurogenic claudication from ligamentum flavum compression is primarily a mechanical and ischaemic phenomenon — and the MiDAS ENCORE randomized trial showed that direct decompression produces more durable relief than repeated injections in this patient population.
MILD® in Canada
Until recently, Canadian patients with lumbar spinal stenosis who were not candidates for or did not wish to undergo open surgery had limited options beyond ongoing conservative management. The MILD® procedure, long established in the United States and covered under Medicare since 2014, was not available here because of the absence of a Health Canada device approval.
That has now changed. Following Health Canada’s regulatory review and approval of the MILD® device, the procedure can be offered to appropriate Canadian patients for the first time. For those living with neurogenic claudication who have not found lasting relief from injections or physiotherapy, and who wish to avoid major spinal surgery, this represents a meaningful new option.
Selected references
- Staats PS, Chafin TB, Golovac S, et al. Long-term safety and efficacy of minimally invasive lumbar decompression procedure for the treatment of lumbar spinal stenosis with neurogenic claudication: 2-year results of MiDAS ENCORE. Reg Anesth Pain Med. 2018;43(8):789–794.
- Jain S, Deer TR, Sayed D, et al. Minimally invasive lumbar decompression: a review of indications, techniques, efficacy and safety. Pain Manag. 2020;10(5):331–348.
- Deer TR, Grider JS, Pope JE, et al. The MIST Guidelines: The Lumbar Spinal Stenosis Consensus Group Guidelines for Minimally Invasive Spine Treatment. Pain Pract. 2019;19(3):250–274.
- Mekhail N, Costandi S, Abraham B, Samuel SW. Functional and patient-reported outcomes in symptomatic lumbar spinal stenosis following percutaneous decompression. Pain Pract. 2012;12(6):417–425.
- Brown LL. A double-blind, randomized, prospective study of epidural steroid injection vs. the mild® procedure in patients with symptomatic lumbar spinal stenosis. Pain Pract. 2012;12(5):333–341.
Frequently Asked Questions
Ketamine influences brain chemistry to restore healthy neural connections, helping patients experience faster relief from symptoms and improving mood stability when traditional treatments are less effective.
The procedure itself typically takes approximately 30–45 minutes per level treated. Including preparation and a brief post-procedure observation period, most patients are discharged within a few hours of arrival.
Recovery is substantially faster than open spine surgery. Most patients return to light activities within one to two days. Walking is actively encouraged from the outset. A structured rehabilitation program typically begins shortly after the procedure. Heavy lifting and strenuous exertion are restricted for a few weeks while the access site heals.
Some patients notice improvement in walking tolerance and leg symptoms within days to weeks. For others, meaningful improvement develops more gradually over the first one to three months as post-procedural swelling resolves and nerve function recovers. Clinical study data show that outcomes continue to improve through the first year and are durable at two-year follow-up.
MILD® can be performed at more than one lumbar level if multiple levels show significant ligamentum flavum hypertrophy. Because no implants are placed and spinal anatomy is not fundamentally altered, the procedure is also compatible with future interventions — including epidural injections, other minimally invasive procedures, or open surgery — should they ever become necessary.
As a newly Health Canada-approved procedure, coverage status under provincial plans is still evolving. Patients are advised to discuss the current funding situation with our office prior to scheduling.
A referral from a family physician or specialist is recommended. A recent lumbar MRI (ideally within the past 12 months) is required prior to assessment, as the imaging review is central to determining candidacy. Patients from across Ontario and other provinces are welcome.
Because the procedure preserves spinal integrity and places no implants, all future treatment options remain fully available. Patients who do not achieve sufficient relief can still proceed with further injections, other minimally invasive approaches, or conventional surgical decompression. MILD® does not foreclose any subsequent pathway.
Epidural steroid injections reduce inflammation around compressed nerve roots and can provide temporary symptom relief, but they do not address the underlying mechanical narrowing of the canal. MILD® physically removes the tissue causing the compression — the thickened ligamentum flavum — which is why clinical trials have demonstrated more durable outcomes compared to repeated injections in patients with this specific pathology.
One of the advantages of MILD® is that it does not require general anesthesia, making it accessible to patients who would be considered high surgical risk due to cardiovascular, pulmonary, or other systemic conditions. Patients on anticoagulation therapy can often be managed with appropriate bridging. Each patient’s medical history is reviewed individually during the assessment process.
Our Specialists
Dr. Michael Gofeld
Specialist in Pain Medicine and Minimally Invasive Spine