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Doctors Step Aside to Maximize Lumbar Fusion

Removing disc material from between two spine bones is not always easy. Doctors want to get in and out without damaging any of the nearby nerve tissue or blood vessels. Only so much disc material can be taken out when the surgery is done from one side of the spine. (Unilateral is the term for doing surgery on one side.) Can enough disc material be removed for a successful operation?

A new method of lumbar fusion that is quickly becoming popular is transforaminal lumbar interbody fusion (TLIF). TLIF can be done unilaterally. Only a small opening is needed to do the operation. Surgical tools are worked through the opening into the disc space. The surgeon must then remove enough disc material to implant a fusion cage filled with bone graft. (A fusion cage is a small device that goes into the disc space to help fuse together the bones just above and below it.)

With the disc out of the way, there's more bone-to-bone contact between the two vertebrae. This is where the fusion is to take place. Scientists know that at least 30 percent of bone-to-bone area is needed for the fusion to support downward pressure on the spine.

The authors of this study wanted to find out just how much of the disc can be removed during unilateral TLIF. They also wanted to know whether it's enough to get the bones to fuse. Doctors worked from one side of the spine and took out as much disc material as they could. The amount was measured. Additional disc material was then taken out by entering the spine from the other side. The researchers found that more than enough disc material could be removed by working only from one side. In fact, nearly twice as much area was made available in the disc space to get a good fusion.

For people facing lumbar spine fusion, this is good news. Doing surgery from only one side means that fewer muscles and nerves need to be moved around during the operation. This means fewer problems and faster healing.

This study raises another question these researchers want answered. Does unilateral TLIF create enough area for the fusion to stay solid during all other types of loads that impact the spine?

References: CPT Matthew A. Javernick, MD, et al. Transforaminal Lumbar Interbody Fusion: Unilateral Versus Bilateral Disk Removal – An In Vivo Study. In The American Journal of Orthopedics. July 2003. Vol. 32. No. 7. Pp. 344-348.

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