The LLIF is an approach to spinal fusion in which the surgeon accesses the intervertebral disc space and fuses the lumbar spine (low back) using a surgical approach from the side (lateral) rather than from the front (anterior) or the back (posterior).
The LLIF is one of a number of spinal fusion options that a surgeon may recommend to treat specific types of lumbar spinal disorders, such as lumbar degenerative disc disease, spondylolisthesis, scoliosis and deformity and some recurrent lumbar disc herniations and types of lumbar stenosis. It cannot be used for all types of lumbar conditions for which spinal fusion is a treatment option. For example, it cannot treat conditions at the lowest level of the spine, L5-S1 or for some people at L4-L5.
It is a minimally invasive type of spine surgery designed to accomplish a spinal fusion with several advantages including:
- Minimal tissue damage
- Minimal blood loss
- Small incisions and scars
- Minimal post-operative discomfort
- Relatively quick recovery time and return to normal function.
Because of the above factors, it is one of a number of options for spinal fusion that are relatively minimally invasive.
The LLIF is a type of interbody fusion, which is a category of fusion in which the disc in the front of the spine is removed and replaced with an implant containing a bone graft to set up the condition for the two vertebrae to fuse together through the disc space. Other types of interbody fusion commonly used to treat lumbar spinal problems include ALIF, PLIF and TLIF, each with its own set of potential advantages and disadvantages.
The LLIF procedure is what is termed a “minimally invasive” procedure. This means that instead of a traditional, larger single incision, the procedure is performed through one or more small incisions and an instrument known as a retractor is used to spread the tissues so that the surgeon can see the spine. Minimally invasive spine surgery technology allows surgeons to reach the spine through several smaller incisions (as opposed to a single large incision). Some surgeons believe minimally invasive surgery is advantageous because it may allow for less tissue trauma, less scarring, shorter hospital stays and less postoperative discomfort, thereby affording a decreased need for post-operative pain medication.
Like all minimally invasive spine surgery techniques, the LLIF procedure was designed to treat disorders of the spine with the least amount of tissue (muscle, ligament, blood vessels and abdominal organs) disruption possible, so that there is minimal tissue-related damage from the surgery and the recovery time is therefore reduced.
Other minimally invasive spine fusion techniques include minimally invasive TLIF procedures, mini laparatomy and transacral approach to L5-S1.
Many surgeons are also able to perform traditional fusion (“open fusion”) using surgical techniques that have many of the characteristics of minimally invasive surgery, including using relatively small surgical incisions, minimal muscle or other soft tissue damage, shorter hospitals stays and minimal postoperative discomfort. For example, some traditional open fusion techniques can be done with a single 2-inch incision in the abdomen or lower back vs. two 1-inch incisions for a minimally invasive approach.
Traditionally, there are a few ways to fuse the spine. One of these ways is known as interbody fusion. Interbody fusion is fusion of two vertebrae between the vertebral bodies (main trunk of the vertebra) in the anterior column (front part of the spine).
In order to fuse two vertebrae together using interbody fusion, the intervertebral disc in the front of the spine must first be removed. In the space created by the removal of the disc, an implant, such as a spacer or cage, will be inserted to help maintain the normal alignment of the spine. Additionally, a bone graft (real pieces of bone used to stimulate bone growth) or bone graft substitute (natural or synthetic material used to replace bone tissue and stimulate bone growth) will be placed in the space made between neighboring vertebrae to help them fuse together.
LLIF vs. ALIF
The LLIF procedure differs from an anterior interbody fusion (ALIF) because the surgeon performs the interbody fusion through an incision in the side of the body as opposed to the front of the body. An ALIF approach requires the organs in the abdomen and some of the major blood vessels to be moved to the side so that the surgeon can reach the spine. In order to minimize the risk of this part of the ALIF procedure, a vascular surgeon or general surgeon usually performs this part of surgery. In an LLIF procedure, the approach from the side does not require any major organs or blood vessels to be moved.
The LLIF procedure can be used for a variety of lumbar spinal disorders that may be treated with spinal fusion. These conditions may include:
- Degenerative disc disease
- Degenerative scoliosis
- Low grade spondylolisthesis
- Spinal deformity
- Foraminal stenosis (a type of spinal stenosis) requiring disc height restoration
- Recurrent lumbar disc herniations
- A thoracic disc herniation
When LLIF is Not an Option
There are a few specific instances where the LLIF procedure could not be performed. Instances in which a patient could not have an LLIF procedure would include:
- A fusion in the disc space between the 5th lumbar and 1st sacral vertebrae (L5-S1) because it is below the level of the pelvic brim, which inhibits access to the disc space from the side.
- For some patients with a low riding L4-L5 level, access from the side through an LLIF may also not be an option
- Some deformities with significant rotation
- High grade spondylolisthesis
- Bilateral retroperitoneal scarring (from a prior abscess or abdominal surgery)
There are a series of steps performed to complete an LLIF spinal fusion:
- First, the patient will be positioned lying on his or her side. Then the surgeon will use X-rays to locate the disc that will be removed.
- Once the disc is located, the surgeon will mark the skin with a marker directly above the disc.
- Then the surgeon will make a small incision (cut) in the flank (low back region of the trunk) and use his or her finger to push away the peritoneum (sac covering the abdominal organs) from the abdominal wall.
- The surgeon will then insert a tube-like instrument known as a dilator into this incision.
- The surgeon will use X-rays to make sure that this dilator is in a good position above the disc.
- The surgeon will then insert a probe (blunt tool) through a muscle known as the psoas muscle. The psoas muscle is a large muscle that runs from the lower spine, wrapping around the pelvic area and attaches at the hip.
Because nerves exiting the spinal column are close to the psoas muscle and can even run right over the surface of it, it is critical that the surgeon be provided with real-time information about the position of the nerves relative to his instruments. Neuromonitoring, the testing of the nerves during surgery to make sure that they are not harmed or irritated during the process, is a critical part of this procedure. This type of nerve monitoring is known as electromyography or EMG. This is not a perfect process and there is still a risk of neural damage during the procedure.
- Once the muscles are split apart, a retractor is put into place to give the surgeon direct access to the spine.
- Once this direct access to the spine is achieved, the surgeon is able to perform a standard discectomy (removing the intervertebral disc) with tools designed to cut and remove the disc.
- After the disc material is removed, the surgeon is able to insert the implant through the same incision from the side. This spacer (cage) will help hold the vertebrae in the proper position to make sure that the disc height (space between adjacent vertebral bodies) is correct and to make sure the spine is properly aligned. This spacer together with the bone graft, is designed to set up an optimal environment to allow the spine to fuse at that particular segment.
- The surgeon will take an X-ray to make sure that the spacer is in the right position.
Sometimes, depending on the diagnosis of the patient, additional support is needed to hold the vertebrae in place. In this case, the surgeon may also decide to put in an additional implant, such as screws, plates or rods for added support. The Lateral Interbody Fusion (LLIF) procedure, like any other surgical procedure, has certain potential risks and complications associated with it.
Possible risks and complications associated with the LLIF include but are not limited to:
- Persistent pain/continued pain after surgery
- Failure to fuse (pseudoarthrosis, or non-union)
- Infection
- Muscle weakness
- Vascular injury (injury of the blood vessels)
- Neurologic injury (nerve or spinal cord damage)
- Urinary tract infection
- Stroke
- Pneumonia
- Deep vein thrombosis (clotting)
- Further progression of existing spinal disease
One particular risk in the LLIF approach is to the lumbar plexus. This is especially true in trying to approach the lower lumbar segments (L4-L5). The retractor used for the LLIF places pressure on the nerves running through the iliopsoas, and although EMG monitoring can help minimize this risk, neural compromise from retraction on the muscle is still a possibility. The damage can range from thigh pain alone to weakness in the quadriceps. The risk is mainly dependent on the size of the patient, the location of the fusion and the experience of the surgeon.
As with any surgical procedure, a discussion detailing all potential risks of the LLIF procedure should take place between the physician and the patient.
Recovery After LLIF
As with any type of spinal fusion surgery, the recovery experience for an LLIF procedure varies from patient to patient.
With an LLIF procedure, the following recovery factors are typical:
- Many patients notice a difference in their pre-operative symptoms (i.e., leg pain, etc.) immediately after surgery. In other patients, pre-operative symptoms often go away gradually.
- Pain at the incision sites after surgery is normal and should be expected. This pain should eventually go away and should be easily controlled with oral pain medication that is prescribed upon discharge from the hospital.
- Because the LLIF surgery only splits muscles (like an ALIF) but does not cut muscles (like a PLIF), many patients are able to get up and walk around the night after they have had surgery.
- The total time a patient spends in the hospital after the surgery depends on several factors, such as the number of vertebral levels that were fused, the severity of the problem and the patient’s overall health.
- Some patients who undergo an LLIF procedure are able to return home the same day as the surgery; others require a stay of a few days or a week in the hospital.
- Most patients are able to return to their normal activities within a few months of surgery.