There are many different ways to treat low back pain. When surgery is needed, there are different options as well. Spinal fusion may be necessary in the case of degenerative disc disease, tumor, infection, deformity, or spinal instability. Just like everything else, fusions can be done in different ways with different approaches.
In this article, two spine surgeons from the San Diego Center for Spinal Disorders in California provide an extensive and detailed overview of extreme lateral interbody fusion (XLIF). Interbody fusion refers to the fact that after removing the disc, the surgeon inserts a metal cage, spacer, or bone graft material in the empty space. Bone is packed in and around the area to help the fusion process along.
Even with interbody fusion, there are different ways to approach the spine. The surgeon may come in from the front of the body. This is called the anterior approach. Surgery from the back of the spine is a posterior approach. Sometimes a posterolateral approach is used — angled between the back and the side. No matter which method is used, the goal is always the same: to restore the disc height and vertebral segment spacing and restore spine stability as close to normal as possible.
Each approach has its advantages and disadvantages. The development of an extreme lateral interbody fusion (XLIF) was in response to some of the problems that occur with other types of fusion procedures. The XLIF is less invasive with a smaller incision, less disruption and damage to the soft tissues, decreased blood loss, and provides a faster recovery.
With the ability to gain access to the disc space without stripping away the muscles, there is a hope that future problems with adjacent segment degeneration can be prevented. Adjacent segment degeneration refers to the breakdown of the next vertebral segment as a result of a transfer of load from the fused site to the next mobile segment.
The XLIF is a new technique of reaching the disc space. The surgeon goes through the side with only disruption of the psoas (hip) muscle. There are no major organs to avoid (as with the anterior approach). There’s no need to strip away large groups of muscles or cut through nerves (as with the posterior or posterolateral approach). The benefits of a minimally invasive approach of this type include decreased blood loss, shorter operative time and hospital stay, and less postoperative pain. Patients recover faster and return to work with fewer sick leave days used up compared with other fusion techniques.
Another advantage of the XLIF is that a larger implant device can be slipped into the disc space. A larger implant means the load is spread out more, the spinal segment can be aligned more accurately, and there’s less chance it will sink down into the endplate. The endplate is a fibrous piece of cartilage between the disc and the bone to support and cushion the disc/spinal segment junction.
XLIF can only be used for fusion of the lumbar spine above the L5 level. For L5S1 fusions, the pelvic bones get in the way of the surgeon trying to reach the lumbar spine. The authors provide pages and pages of descriptions, photographs, drawings, X-rays, and intraoperative views of the XLIF procedure. They take the reader through the five major steps of this procedure: patient positioning, access to the body, passing through the psoas to the disc, removing the disc, and inserting the implant.
Special X-ray techniques such as fluoroscopy and real-time electromyography (EMG) are used to guide the surgeon and monitor the patient. Using these tools, the surgeon can move safely through the body to the spine avoiding the abdominal contents and without damaging vital nerves, blood vessels, and soft tissues.
The most difficult part of the operation is to move through the psoas muscle without disrupting the lumbar nerve plexus. That’s where EMG comes in handy. The tool used for the XLIF has a tiny EMG electrode on the tip giving the surgeon continuous feedback on the location of the psoas muscle. The fluoroscope is used once again after the disc material has been removed to put the spacer in place and to pack it with bone graft material.
Patients often go home within one to three days after the XLIF surgery. Sometimes a special brace is needed to support the spine during the healing and recovery process. But more often, patients go home and return to their daily activities and work quickly and easily. That’s not to say problems don’t ever occur. There are some potential complications from XLIF.
If the lumbar plexus or genitofemoral nerve is damaged during the procedure, thigh and/or groin pain and numbness are possible. Trauma to the psoas muscle can also produce hip pain and weakness. Most of these symptoms are temporary and will go away in time (six weeks to six months).
The authors say that in all the small studies done so far, the results have been good. There’s been no question about the safety and effectiveness of XLIF for interbody fusion. They have even used it with multilevel fusions in patients with other problems like scoliosis. But the studies are limited and with only a few patients. Larger, randomized controlled trials comparing XLIF to other fusion operations will provide the rest of the story in time.