Minimally Invasive Spine Surgery
Minimally invasive spine surgery (MISS) is sometimes called less invasive spine surgery. In these procedures, doctors use specialized instruments to access the spine through small incisions.
In general, the goal of minimally invasive spine surgery (MISS) 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. It does not involve a long incision, it avoids significant damage to the muscles surrounding the spine. Typically, this results in less pain after surgery and a faster recovery.
In a traditional open surgery, the doctor makes an incision that is 5 to 6 inches long, then moves the muscles to the side in order to see the spine. With the muscles pulled to the side, the surgeon can access the spine to remove diseased and damaged bone or intervertebral disks. The surgeon can also easily see to place screws, cages, and any bone graft materials necessary to stabilize the spinal bones and promote healing.
One of the major drawbacks of open surgery is that the pulling or “retraction” of the muscle can damage both the muscle and the surrounding soft tissue. Although the goal of muscle retraction is to help the surgeon see the problem area, it typically affects more anatomy than the surgeon requires. As a result, there is greater potential for muscle injury, and patients may have pain after surgery that is different from the back pain felt before surgery. This can lead to a lengthier recovery period. The larger incision and damage to soft tissues may also increase both blood loss and the risk for infection.
Minimally invasive spine surgery was developed to treat spine problems with less injury to the muscles and other normal structures in the spine. It also helps the surgeon to see only the location where the problem exists in the spine. Other advantages of MISS include smaller incisions, less bleeding, and shorter stays in the hospital.
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:
- Better cosmetic results from smaller skin incisions (sometimes as small as 2 centimeters)
- Less blood loss from surgery
- Reduced risk of muscle damage since less or no cutting of the muscle is required
- Reduced risk of infection and postoperative pain
- Faster recovery from surgery and less rehabilitation required
- Diminished reliance on pain medications after surgery
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.
MIS surgeries are generally used to treat the following conditions
- Degenerative disc disease
- Herniated disc
- Lumbar spinal stenosis
- Spinal deformities such as scoliosis
- Spinal infections
- Spinal instability
- Vertebral compression fractures
- Spinal tumors
Minimally Invasive Spine Surgery Procedure – How It Works
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:
Use of a tubular retractor:
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, an endoscopic or microscope is used to focus 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.
Percutaneous placement of screws and rods:
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 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.
Direct lateral access routes:
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.
Thoracoscopic access route:
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, thoracoscopic access relies on multiple small incisions through which working ports and cameras can be inserted to facilitate surgery.
Common Minimally Invasive Spine Surgeries
Discectomy: Discectomy is surgery to remove lumbar (low back) herniated disc material that is pressing on a nerve root or the spinal cord. It tends to be done as microdiscectomy, which uses a special microscope to view the disc and nerves. This larger view allows the surgeon to use a smaller cut (incision) and causes less damage to surrounding tissue.
Before the disc material is removed, a small piece of bone (the lamina) from the affected vertebra may be removed. This is called a laminotomy or laminectomy which allows better visibility of the herniated disc.
Spinal Decompression: Spinal stenosis is a condition resulting in narrowing of the spine. The narrowing of the spine is often due to bone spur formation, arthritis, thickening of the spinal ligaments and possibly bulging of the spinal discs. It is more common in older people. However, it occasionally occurs even in young patients, especially if there is a genetic component. 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 and a retractor is placed on either side of the spine. This approach prevents disruption of the midline ligaments and bone. Using the two retractors, the surgeon can remove the lamina and the disk, place the bone graft into the disk space, and place screws or rods to provide additional support.
Sometimes additional bone graft is used besides the patient’s own bone to improve the likelihood of healing.
As with any operation, there are potential risks associated with MISS. The complications of MISS are similar to those of open spinal fusion surgeries; however, some studies show a reduced infection rate for MISS. Before the surgery, each of the risks will be discussed and will take specific measures to help avoid potential complications. The potential complications of MISS include:
- Infection. Antibiotics are given to the patient before, during, and often after surgery to lessen the risk of infections.
- Bleeding. A certain amount of bleeding is expected, but this is not typically significant.
- Pain at graft site. A small percentage of patients will experience persistent pain at the bone graft site.
- Recurring symptoms. Some patients may experience a recurrence of their original symptoms.
- Pseudarthrosis. This is a condition in which there is not enough bone formation and a spinal fusion does not completely heal. If this occurs, a second surgery may be needed in order to obtain a solid fusion. Patients who smoke are more likely to develop a pseudarthrosis.
- Nerve damage. It is possible that the nerves or blood vessels may be injured during these operations. These complications are very rare.
- Blood clots. Formation of blood clots in the legs is another uncommon complication after surgery. They pose a significant danger if they break off and travel to the lungs.
Minimally invasive procedures can shorten hospital stays. The exact length of hospital stay will vary with from patient to patient and with the individual procedure but, in general, MISS patients go home on the same day or in 1 to 2 days. Most patients having traditional surgery stay in the hospital for 3 to 5 days.
Since minimally invasive techniques do not disrupt muscles and soft tissues, it is believed that postoperative pain is less than pain after traditional open procedures. Although patients can still expect to feel some discomfort, advancements in pain control now make it easier to manage and relieve pain.
Physical therapy may be recommended to regain strength and speed up recovery. This will depend on the procedure and your general physical condition. Specific exercises will help you become strong enough to return to work and daily activities.
In case of fusion procedure, it may be several months before the bone is solid. During this healing time, the fused spine must be kept in proper alignment.
The time it takes to return to your daily activities after MISS depends upon the procedure and condition. Follow-up evaluation will be done to make sure that recovery is progressing as expected.