Minimally invasive lumbar decompression (MILD), also known as percutaneous image-guided lumbar decompression (PILD), is a minimally invasive treatment option for some people with spinal stenosis in the lower back.

What is minimally invasive lumbar decompression?

Minimally invasive lumbar decompression is a procedure to treat spinal stenosis (narrowing of the spinal canal) in the lower back (the lumbar region of the spine). During the MILD procedure, the surgeon removes small bits of thickened ligament in the lower spine to restore the space in the spinal canal and reduce pressure on surrounding nerves.

The procedure is minimally invasive, meaning it uses a small incision, specialized tools and local anesthesia with mild sedation. This leads to shorter recovery time and minimal complications, and patients can go home the same day.

The MILD procedure is usually performed by pain management experts who are specially trained in this procedure.

Who may benefit from the MILD procedure?

MILD is used to treat people who have lumbar spinal stenosis. This condition occurs when the spinal cord becomes compressed or pinched. One of the causes of this compression is thickening of a ligament in the spinal canal called the ligamentum flavum. 

This ligament runs along the posterior aspect of the spinal canal. As it grows thicker and hardens, it can buckle and push on the spinal cord and nerve roots, causing pain, numbness, tingling or cramping in the lower back, areas below the waist and in the legs. The pain usually increases when the person is standing or walking. Pain subsides when bending forward at the waist or when sitting down. If you are experiencing these symptoms, it’s possible that the cause is excessive ligament tissue, which can be removed with the MILD procedure.

People of any age who have painful lumbar spinal stenosis that is not well-managed with medications, physical therapy or therapeutic injections are good candidates for the MILD procedure. It can be especially beneficial for older people who may not be able to tolerate more invasive surgery due to other health conditions.

Talk to your doctor to understand whether your symptoms are caused by lumbar spinal stenosis and if the MILD procedure is right for you. The procedure may not be recommended for people who have had spine surgery or who have an infection in the part of the spine affected by stenosis.

Preparing for minimally invasive lumbar decompression

If you have not had recent magnetic resonance imaging (MRI) of your spine, your doctor may refer you to have this test completed. The imaging will provide important views of the spinal column and help determine if you have lumbar spinal stenosis that could be treated with the MILD procedure.

Inform your doctor of any medications you are currently taking (especially if you are taking any antibiotics or blood thinners), along with any allergies you may have. You may need to adjust or pause certain medications before the procedure.

Avoid eating at least six hours before the procedure. You will want to bring someone with you who can drive you home.

While general anesthesia is usually not needed for the MILD procedure, you can discuss anesthesia options with your doctor to ensure you are comfortable during the procedure.

What happens during the MILD procedure?

MILD is an outpatient procedure, which means you don’t need to be admitted to the hospital.

The MILD procedure typically takes approximately one hour to complete. During the procedure:

• A patient lies on the stomach on a special operating table that allows X-rays to pass through.
• The doctor applies local anesthesia to the lower back.
• Using fluoroscopic guidance, the doctor inserts a needle into the lower back to inject a contrast dye into the epidural space (the area inside the spinal canal). This dye is visible on an X-ray, and helps the doctor see the compressed area of the spine.
• The doctor makes a small incision in the side of the lower spine and inserts a small tube to gain access to the problem area.
• Small tools are inserted through the tube, and the doctor guides them to remove bone and thickened ligament tissues that are pressing on the nerves and compressing the spinal cord. This process is repeated on both sides of the spine.
• The doctor confirms that the spinal canal has been decompressed by checking an X-ray to see whether the dye flows freely.
• Once the spinal canal is cleared, the doctor closes the incision with adhesive strips or dissolvable sutures.

Sometimes, the MILD procedure can be performed on multiple levels of the spine during the same procedure. This may be needed if there is more than one area of spinal cord compression in the lower back.

Recovery After Minimally Invasive Lumbar Decompression

The Day of the Procedure

Once the surgery is completed, you will rest in a recovery room until the anesthesia wears off. The care team will monitor you for a short period. If there are no complications, you can go home the same day.

It is important not to drive, bathe or swim on the day of the MILD procedure. Some soreness and pain near the incision site are expected. Your doctor may prescribe pain medication or a muscle relaxer to help with pain or muscle spasms.

The First Week After the Procedure

There may be slight pain and swelling around the incision site, which will lessen over the next few days. Avoid heavy lifting or strenuous activities. If you still have dressing around the incision site, you can remove it by the end of the first week. Depending on the physical demands of your job, you may be able to return to work within a few days after the MILD procedure.

The First Month After the Procedure

During your first month after the MILD procedure, you will begin returning to your normal activities. After the first few weeks, most of the pain and swelling should have subsided. Notify your doctor if you feel the pain is not reducing or may be increasing. Continue to avoid strenuous activities and heavy lifting.

If your doctor prescribed physical therapy as part of the recovery process, it will start about two weeks after the MILD procedure.

After a Month

By this time, many people will have made significant progress in their recovery and are able to participate in sports and otherwise increase activity as recommended by their doctor.

Risks and Complications of the MILD procedure

Minimally invasive surgeries, such as MILD, have a reduced risk of complications, scarring and postoperative pain compared with open surgeries. Your care team will take precautions to address risks and prevent complications, which may include:

• Infection
• Bleeding
• Damage to nerves or the spinal cord
• Epidural hematoma or spinal cord bruise
• Dural leak or tear – fluid leaks from the spinal canal
• Spinal instability

Overall, research has shown that MILD is as safe as epidural steroid injections, while offering pain relief that is greater and more durable than the relief provided by those injections. The procedure has been cleared by the U.S. Food and Drug Administration since 2006.

How effective is MILD in treating lumbar spinal stenosis pain?

Many people with lumbar spinal stenosis experience noticeable pain relief immediately after the MILD procedure. In the days to weeks after the procedure, additional improvement is expected (see a related research study), including:

• Ability to stand longer with less pain (an average increase from 8 to 56 minutes)
• Ability to walk farther with less pain (an average increase from 246 feet to 3,956 feet)
• Better posture
• Decreased use of opioid pain medications

It may take about three to 12 months after the MILD procedure for the full benefit to take effect. 

For most patients, research shows that pain relief from a MILD procedure can last years after the surgery.

What happens if pain returns after the MILD procedure?

While the MILD procedure offers lasting pain relief to many people, the effectiveness varies from person to person, and the effects may not last forever. Talk to your doctor if the symptoms return or if new pain is felt in another part of the spine. Your doctor can recommend the next steps, which may include:

• Nonsurgical treatments – Physical therapy, pain management techniques or medications for pain and inflammation.
• Repeat MILD procedure – The MILD procedure can be performed on a different level of the spine if there is another area of compression.
• Other spine surgeries – These procedures offer different approaches to treating lumbar spinal stenosis. Some of these can be done with minimally invasive techniques using small incisions and a special camera, while others need a larger incision:
  • Laminectomy and laminotomy remove or reshape parts of the vertebrae.
  • Disk removal/replacement procedures can address deteriorated or bulging disks.
  • Spinal fusion helps stabilize a part of the spine.
  • Spinal spacers help push the vertebrae apart and keep them aligned.

One study showed that in the five years after having the MILD procedure, only 12% of people needed spine decompression surgery.

Is the MILD procedure covered by insurance?

MILD is approved in the U.S. as part of Medicare and Medicare Advantage plans. It is also covered by various private insurers. Check with your insurance company to determine your coverage.