In general, the goal of minimally invasive spine surgery (MIS) surgery is to stabilize the vertebral bones and spinal joints and/or relieve pressure being applied to the spinal nerves — often a result of conditions such as a spinal instability, bone spurs, herniated discs, scoliosis or spinal tumors.
As opposed to open spine surgery, minimally invasive surgical approaches can be faster, safer and require less recovery time. Because of the reduced trauma to the muscles and soft tissues (compared to open procedures), the potential benefits are:
In addition, some MIS surgeries are performed as outpatient procedures and utilize only local anesthesia — so there is less risk for an adverse reaction to general anesthesia.
As with any surgical procedure, no matter how minimal, there are certain risks associated that include but are not limited to:
And, though uncommon, there is always a small chance that the initial MIS surgery cannot be completed, requiring either a second procedure or full open surgery.
Because the spinal nerves, vertebrae and discs are located deep inside the body, any approach to gain access to the spinal area requires moving the muscle tissue out of the way. In general, this is facilitated by utilizing a small incision (s) and guiding instruments and/or microscopic video cameras through these incisions. Contrary to popular belief, lasers are very rarely used in MIS surgeries.
A number of methods can be used to minimize trauma during MIS surgery. Some of the more common techniques include:
This technique involves progressive dilation of the soft tissues, as opposed to cutting directly through the muscles. By using tubes to keep the muscles out of the way, the surgeon can work through the incision without having to expose the area widely. Sometimes, the surgeon will also utilize an endoscopic or microscope focused down the tube to assist with performing the surgery through a minimal access strategy. Once the procedure is complete, the tubular retractor can be removed, allowing the dilated tissues to come back together. Depending on the extent and type of surgery necessary, incisions can often be small.
Depending on the condition of the patient, it may be necessary to place instrumentation, such as rods and screws, to stabilize the spine or to immobilize the spine to facilitate fusion of the spinal bones. Traditional approaches for placement of screws requires extensive removal of muscle and other tissues from the surface of the spine.
However, percutaneous (which means “through the skin”) placement typically involves inserting rods and screws through relatively small skin incisions without cutting or dissecting the underlying muscle. With the aid of X-ray images, guidewires are placed through the skin and into the spinal vertebrae along the desired paths for the screws. Then, screws are placed over the guidewires and follow the path of the wires. These screws have temporary extenders that extend outside of the skin and subsequently removed after helping to guide passage of rods to connect and secure the screws.
In some cases — especially those involving the lumbar spine — approaching the spine from the side of the body results in reduced pain, due to the limited amount of muscle tissue blocking the way. This approach is typically performed with the patient on his or her side. Then, a tubular retractor docks on the side of the spine to enable access to the spine’s discs and bones.
Depending on the patient’s condition, it may be necessary to access the front portions of the thoracic spine, located in the chest and surrounded by the heart and lungs. Traditional access approaches often involve opening the chest through large incisions that may also require removal of one or more ribs. However, thoracscopic access relies on multiple small incisions through which working ports and cameras can be inserted to facilitate surgery.
A number of specific techniques have been deployed for MIS surgery. Though the field continues to develop, the list below highlights some of the most common options:
Discetomy: Spinal discs are essentially elastic rings with soft material inside that serve as cushions between the vertebral bones. If the elastic ring becomes incompetent or weakened, the soft tissue inside can extrude — or herniate — outside of the elastic ring. The herniated disc material can compress the nerves passing by, thus causing pain. If surgical treatment is recommended to trim or remove the herniated disc, it may be possible to perform this procedure with MIS surgery using tubular dilators and a microscope or endoscope.
Spinal decompression: Spinal stenosis, which is a narrowing of the vertebral column, is a common condition that can result in compression of the nerves. This can produce a variety of symptoms, including pain, numbness and muscle weakness. If surgery is recommended, it may be possible to remove the bone and soft tissues causing the nerve compression through an MIS approach using tubular dilators and a microscope or endoscope. The more common decompressive procedures include laminectomy and foraminotomy.
MIS TLIF (Transforaminal lumbar interbody fusion):
This is a MIS technique that is performed in patients with refractory mechanical low back and radicular pain associated with spondylolisthesis, degenerative disc disease and recurrent disc herniation. The TLIF approach may also have potential in patients with low back pain caused by postlaminectomy instability, spinal trauma or for treating pseudoarthrosis. The procedure is performed from the back (posterior) with the patient on his or her stomach.
A doctor will be able to tell you which MIS surgeries, if any, might be an option for treating your spinal condition. In some situations, MIS surgery may not be as safe or effective as traditional open surgery. If so, your doctor will be able to inform you about the relative risks and benefits. In addition, there are some conditions that are not truly accessible with MIS surgery.