BMN Blog

APR 05
A Sideways Look at Spinal Fusion

While there are seemingly countless spinal surgical approaches and techniques, all spinal surgeries fall into one of two categories: decompression or stabilization. Decompression involves taking pressure off neurologic structures including the spinal cord and, more commonly, nerve roots to improve function and relieve pain. Stabilization involves restoring structure to one or more spinal segments, i.e. two adjacent vertebra and the intervening disc, by creating an environment for bone to grow from one vertebra to the next. This may be performed to treat gross instability from a traumatic fracture or chronic instability from a degenerative spondylolisthesis.


The evolution of spinal fusion began with placement of bone graft along the posterior spine. While easy to perform, there are limitations to a successful posterior fusion including decreased surface area for bone growth after a decompressing laminectomy. In addition, this approach results in diminished vascularity and nutrition to the fusion bed from surrounding muscle injury which can inhibit bone formation. Anterior surgical approaches improved graft options, but included risks for different complications such as vascular injury and ileus development in the lumbar spine and lung deflation sequelae from anterior thoracic approaches.


A newer approach to spinal fusion is generically called the “lateral approach” with trademarked names such as XLIF (eXtreme Lateral Interbody Fusion) and DLIF (Direct Lateral Interbody Fusion). First described in the American literature in 2003, this technique involves approaching the spine from the side of the body.


The benefits of this technique include providing a large bone graft into the disc space which is where 80 percent of forces are borne by the spine. This allows for more aggressive correction of deformities and restoration of disc height. These mechanical alterations open the spinal canal and neuroforamen resulting in “indirect” decompression, i.e. taking pressure off nerve roots without directly visualizing the nerves through a traditional laminectomy approach. In a 2010 radiographic study, the authors identified a 25 percent increase in neuroforaminal area and a 33 percent increase in spinal canal diameter from indirect decompression alone after lateral spinal fusion surgery.


In addition, this surgical approach includes small penetrations of the oblique muscles (external oblique, internal oblique and transverse abdominis) and psoas muscle (which resides along each side of the spine and produces hip flexion). Due to the lack of muscle stripping from the spine which is often required for traditional posterior approaches, there is significantly less blood loss, dead space creation, and muscle damage. These factors decrease infection risk and speed up recovery. The typical patient will be discharged the day after surgery rather than three to four days after traditional open posterior fusions. In a 2010 study of 60 octogenarians undergoing either lateral or posterior based fusion surgery, the authors found a blood transfusion rate of 0 percent versus 70 percent, discharge to home rate of 92.5 percent versus 0 percent, and a six-month mortality rate of 2.5 percent versus 20 percent.


This minimally invasive approach has evolved to treat thoracic pathologies such as tumor and discitis/osteomyelitis without the need for lung deflation and chest tube insertion.


So, when treatment options include a spinal fusion, don’t turn around and ignore the problem. Just take a look at it from the side, instead.


Christopher Heck, MD is a spine surgeon who practices at Southlake Orthopaedics Sports Medicine and Spine Center.

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