The MILD procedure (minimally invasive lumbar decompression) is an outpatient spine treatment that removes small pieces of thickened ligament tissue pressing on nerves in the lower back. It’s designed specifically for people with lumbar spinal stenosis, a condition where the spinal canal narrows and squeezes the nerves that run through it. The entire procedure is done through an incision roughly 1 centimeter long, about the width of a fingertip, using local anesthesia and light sedation.
How the Spinal Canal Narrows
Running along the back wall of your spinal canal is a band of connective tissue called the ligamentum flavum. In a healthy spine, this ligament is thin and flexible. Over time, it can thicken, harden, and buckle inward, crowding the spinal cord and nerve roots. When this ligament measures more than 2.5 millimeters on an MRI, it’s considered hypertrophied and may be a candidate for treatment.
This thickening often happens alongside other age-related changes: bulging discs, bone spurs, and stiffening of the small joints in the spine. Together, these changes reduce the available space in the spinal canal. The result is lumbar spinal stenosis, which affects the lower back and can cause pain, numbness, tingling, or cramping in the legs and buttocks. Many people with this condition notice their symptoms worsen when standing or walking and improve when they sit down or lean forward, a pattern called neurogenic claudication.
What Happens During the Procedure
MILD is typically performed with local anesthesia and light sedation rather than general anesthesia. You lie face down, and the doctor numbs the lower back before making a small incision off to one side of the spine. A thin tube, roughly the diameter of a pen cap (about 5 millimeters), is inserted to create a pathway to the compressed area.
Before any tissue is removed, the doctor injects contrast dye into the epidural space and uses real-time X-ray imaging (fluoroscopy) to visualize exactly where the compression is occurring. A specialized sculpting tool is then guided through the tube to carefully shave away thickened ligament and, when necessary, small bits of bone that are crowding the spinal canal. This process is repeated on both sides of the spine. At the end, the doctor checks the X-ray again to confirm that the dye flows freely through the decompressed area.
Because the procedure works through a tiny portal and doesn’t remove large sections of bone, the structural architecture of the spine stays intact. No implants, screws, or spacers are placed. This is a key distinction from traditional open surgery like laminectomy, where larger portions of bone are removed and spinal mechanics can be disrupted.
Who Is a Good Candidate
The ideal candidate has mild to moderate lumbar spinal stenosis caused primarily by ligament thickening, with or without some disc bulging or joint degeneration. Imaging should show the ligament measuring over 2.5 millimeters. The general recommendation is that patients try conservative treatments like physical therapy, anti-inflammatory medications, or epidural steroid injections for three to six months before considering the procedure.
Not everyone qualifies. The procedure is not appropriate for people with:
- Grade II or higher spondylolisthesis, where one vertebra has slipped significantly over another, indicating spinal instability
- Severe canal or foraminal stenosis, where the narrowing is too advanced for this approach
- Previous spine surgery at the same level
- Significant epidural lipomatosis, an excess buildup of fat tissue in the spinal canal
- Severe neurogenic claudication with an inability to walk more than 10 feet
If there’s any suspicion of vertebral slippage, your doctor will likely order flexion-extension X-rays, where you bend forward and backward while images are taken, to check for instability before clearing you for the procedure.
How MILD Compares to Steroid Injections
A randomized, double-blind study comparing MILD directly to epidural steroid injections in 38 patients with neurogenic claudication found that MILD delivered significantly greater pain relief and functional improvement. At both 6 and 12 weeks, the MILD group reported better pain reduction and improved ability to walk and stand. Patient satisfaction scores were also notably higher in the MILD group.
Epidural steroid injections can provide temporary relief by reducing inflammation around compressed nerves, but they don’t address the physical cause of the narrowing. MILD removes the tissue responsible for the compression, which is why the benefits tend to last longer. That said, steroid injections are still a reasonable first step, since they’re less invasive and can help clarify whether nerve compression is actually driving your symptoms.
Long-Term Results
The MiDAS ENCORE study, one of the larger clinical trials evaluating the procedure, tracked patients for two years. All outcome measures showed meaningful improvement that held up through six months, one year, and two years of follow-up. At the two-year mark, disability scores improved by an average of 22.7 points on a standard 100-point scale, and pain scores dropped by an average of 3.6 points on a 10-point scale. Both changes are well above the threshold that clinicians consider meaningful.
Patients also reported improved walking ability and reduced symptom severity over the full follow-up period. These results suggest the procedure provides durable relief rather than a short-term fix, though individual outcomes vary depending on the severity of stenosis and other contributing factors.
Recovery and What to Expect After
Because MILD doesn’t disrupt the bony structure of the spine and uses only a small incision, recovery is considerably faster than traditional open surgery. Most people go home the same day. The incision is small enough that it typically requires only a bandage or a single stitch.
Patients generally resume light daily activities within a few days. The absence of general anesthesia also means you avoid the grogginess, nausea, and longer recovery window that come with being fully sedated. Your doctor will give you specific guidance on when to return to exercise, physical therapy, or any heavy lifting based on your individual situation, but the overall recovery arc is measured in days rather than weeks.
Insurance and Medicare Coverage
Coverage for MILD varies by insurer. Medicare’s current national policy, last reviewed in 2016, classifies the procedure as covered only when performed as part of an approved clinical study. This means that under standard Medicare, MILD is not automatically reimbursed outside of a research context. Some private insurers do cover the procedure, but policies differ. If you’re considering MILD, it’s worth confirming coverage with your insurance provider before scheduling, as out-of-pocket costs for spinal procedures can be substantial.