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Fusion Rates and Complications After Lumbar Interbody Fusion

For almost 30 years surgeons have been fusing the lumbar spine using the popular transforaminal lumbar interbody fusion (TLIF) technique. The surgeon approaches the spine from the side rather than from the front (anterior approach) or the back (posterior approach).

The TLIF method of lumbar fusion has many advantages. The lateral approach gives the surgeon access to the disc and disc space without applying excess pull or traction on the nearby spinal nerve(s). With a lateral approach, it is only necessary to remove one spinal joint (rather than the joints on both sides of the spinal level being fused) in order to get to the disc space.

The procedure was first done with an open incision approach called an open transforaminal lumbar interbody fusion or oTLIF. This procedure required cutting through the spinal muscles to get to the spine.

Over time, surgical technology and equipment have improved and advanced so that the procedure could be done as a minimally invasive (MI) approach. Minimally invasive means a very small incision is made.

In a minimally invasive TLIF (referred to as mTLIF), a long thin tube is passed down through the skin, fascia, and muscle down to the spine. It is not necessary to dissect (cut through) all these layers of soft tissue. Surgical instruments and hardware (cages, screws) used to fuse the spinal segment are passed through this tubular retractor system.

In theory, a minimally invasive approach reduces blood loss during the procedure and postoperative pain afterwards. Hospital stays are shorter with the mTLIF, which means lower costs. Other advantages of the minimally invasive approach have been reported. For example, there is less damage to the muscles and less tissue trauma overall. The surgeon uses 3-D navigational (surgical) tools that allow him or her to see the correct pathway and avoid injury to nerve tissue.

That all sounds good in theory, but how do the results of these two different ways to perform a TLIF compare? A study was done to compare fusion rates and complications for the open transforaminal lumbar interbody fusion (oTLIF) with the minimally invasive TLIF (mTLIF). The method used to do this comparison was a literature review.

By conducting a computer search, the authors of this study found 23 studies including a total of 1028 patients who had the TLIF procedure. There were an equal number of men and women in the total database. Ages ranged from 38 to 65 years old. There were twice as many oTLIF (open) procedures compared to the mTLIF (minimally invasive) approach.

Most of the studies were case series (a lower level of evidence). But by combining the results of multiple studies like this creates a meta-analysis. This research tool is helpful when the number of patients in each case series is too small to achieve significance on its own.

The results of this comparison showed nearly equal fusion rates between the two procedures. Open TLIF had a 90.9 per cent fusion rate. Minimally invasive TLIF had a slightly higher rate at 94.8 per cent. Rates were determined in follow-up at least six months after the surgery. Some fusion rates were for follow-up periods as far out as 46 months (almost four years) after surgery.

What about complications? The types and numbers of problems encountered by patients in both groups postoperatively were also similar. For example, complications after the open TLIF were calculated at 12.6 per cent. Complications after the minimally invasive TLIF were reported at 7.5 per cent.

Typical complications in both groups included dural tears (lining of the spinal cord) with leakage of the cerebrospinal (CSF) fluid, leakage of the cerebrospinal fluid, infection, misplaced screws, and radiculopathy (pain down the leg from irritation or compression of the spinal nerve root).

As predicted, the minimally invasive (mTLIF) method may be slightly safer than the open procedure. The difference in complication rates may be due to the more frequent use of bone morphogenetic protein (BMP) in the mTLIF group. Bone morphogenetic protein was developed as a grafting technique to help speed up bone healing.

Half of all the mTLIF procedures were done with bone morphogenetic protein (BMP) and may be the reason why complication rates were lower with the mTLIF procedure. But the intent of this study was not to assess the BMP technique as a factor in results. The authors suggest future studies are needed to compare lumbar fusion with and without BMP for oTLIF versus mTLIF.

For now, they concluded that fusion rates are good-to-excellent for both open and minimally invasive TLIF. Efforts to reduce complications from soft tissue trauma and dissection using the mTLIF seem to be successful. This is the first study to make these comparisons. As such, the results provide a "benchmark" or baseline for future studies to verify or add to these findings.


Ray H. Wu, BS, et al. Minimal Access Versus Open Transforaminal Lumbar Interbody Fusion. In Spine December 15, 2010. Vol. 35. No.26. Pp. 2273-2281.

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