Microdiscectomy (Microdecompression) Spine Surgery
In a microdiscectomy or microdecompression spine surgery, a small portion of the bone over the nerve root and/or disc material from under the nerve root is removed to relieve neural impingement and provide more room for the nerve to heal.
A microdiscectomy is typically performed for a herniated lumbar disc and is actually more effective for treating leg pain (also known as radiculopathy) than lower back pain.
Impingement on the nerve root (compression) can cause substantial leg pain. While it may take weeks or months for the nerve root to fully heal and any numbness or weakness to get better, patients normally feel relief from leg pain almost immediately after a microdiscectomy spine surgery.
How Microdiscectomy Surgery is Performed
A microdiscectomy is performed through a small (1 inch to 1 1/2 inch) incision in the midline of the low back.
First, the back muscles (erector spinae) are lifted off the bony arch (lamina) of the spine. Since these back muscles run vertically, they can be moved out of the way rather than cut. The surgeon is then able to enter the spine by removing a membrane over the nerve roots (ligamentum flavum), and uses either operating glasses (loupes) or an operating microscope to visualize the nerve root.
Often, a small portion of the inside facet joint is removed both to facilitate access to the nerve root and to relieve pressure over the nerve. The nerve root is then gently moved to the side and the disc material is removed from under the nerve root.
Importantly, since almost all of the joints, ligaments and muscles are left intact, a microdiscectomy does not change the mechanical structure of the patient’s lower spine (lumbar spine).
Indications for Microdiscectomy Surgery
In general, if a patient’s leg pain due to a disc herniation is going to get better, it will do so in about six to twelve weeks. As long as the pain is tolerable and the patient can function adequately, it is usually advisable to postpone back surgery for a short period of time to see if the pain will resolve with non-surgical treatment alone.
If the leg pain does not get better with nonsurgical treatments, then a microdiscectomy surgery is a reasonable option to relieve pressure on the nerve root and speed the healing. Immediate spine surgery is only necessary in cases of bowel/bladder incontinence (cauda equina syndrome) or progressive neurological deficits. It may also be reasonable to consider back surgery acutely if the leg pain is severe.
A microdiscectomy is typically recommended for patients who have:
- Experienced leg pain for at least six weeks
- Not found sufficient pain relief with conservative treatment (such as oral steroids, NSAID’s, and physical therapy).
However, after three to six months, the results of the spine surgery are not quite as favorable, so it is not generally advisable to postpone microdiscectomy surgery for a prolonged period of time (more than three to six months).
Microdiscectomy Success Rates
The success rate for microdiscectomy spine surgery is approximately 90% to 95%, although 5% to 10% of patients will develop a recurrent disc herniation at some point in the future. A recurrent disc herniation may occur directly after back surgery or many years later, although they are most common in the first three months after surgery. If the disc does herniate again, generally a revision microdiscectomy will be just as successful as the first operation. However, after a recurrence, the patient is at higher risk of further recurrences (15% to 20% chance).
For patients with multiple herniated disc recurrences, a spinal fusion may be recommended to prevent further recurrences. Removing the entire disc space and fusing the level is the most common way to absolutely assure that no further herniated discs can occur. If the posterior facet joint is not compromised and other criteria are met, an artificial disc replacement may be considered.
Recurrent herniated discs are not thought to be directly related to a patient’s activity, and probably have more to do with the fact that within some disc spaces there are multiple fragments of disc that can come out at a later date. Unfortunately, through a posterior microdiscectomy spine surgery approach, only about 5 to 7% of the disc space can be removed and most of the disc space cannot be visualized.
Microdiscectomy Risks & Complications
As with any form of spine surgery, there are several risks and complications that are associated with a microdiscectomy, including:
Dural tear (cerebrospinal fluid leak) — this occurs in 1% to 2% of these surgeries, does not change the results of surgery, but post-operatively the patient may be asked to lay recumbent for one to two days to allow the leak to seal.
- Nerve root damage
- Bowel/bladder incontinence
However, the above complications for microdiscectomy spine surgery are quite rare.