Off Balance? Lumbar Stenosis & Fusion

There is a mysterious variation in the rates of lumbar fusion around the country; surgeons in Idaho Falls fuse 20 times more often than those in Bangor, Maine¹. Just a few months ago, the Wall Street Journal² wrote about 5 surgeons in Kentucky who managed to raise their one institution to third place in the total number of spinal fusions performed on Medicare patients nationally. For the diagnosis of lumbar stenosis, the New York Times³ reported on Deyo et al’s⁴ discovery of a 15-fold rise in the rate of complex spinal fusions between 2002 and 2007 while the rate of the diagnosis itself and of the classic decompression procedure actually declined slightly. Why the shift to fusions, when only a decade earlier, the standard teaching was:

“Fusion should be reserved for the approximately 5 to 10% of patients in whom there is clinical evidence of instability prior to surgery or for the few who develop slippage following laminectomy and facetectomy.”⁵

Various explanations are available, from the development of safer technology, to improved imaging that better identifies spinal pathology, to the increasing popularity of spine surgery as a field. The more cynical of these opinions is that fusion surgery has become a highly lucrative field for all parties, the device makers (the US market for spinal implants is expected to reach $8 billion by 2016), physicians and, at least for now, hospitals. Where then does the truth lie, and which lumbar stenosis patients should undergo these fusion procedures? This article will address these questions and give some approaches to management of lumbar stenosis. First, some anatomy.

The 5 lumbar vertebrae provide nearly all of the truncal flexibility in humans. Each pair of adjacent lumbar vertebrae is joined by three articulating bone-cartilaginous interfaces, a large intervertebral disc and two small facet joints (Figure 1). These surround the spinal canal on triangular sides, covered by ligaments over the posterior vertebrae, over the facets and between the laminae.

In lumbar stenosis, the ligamentum flavum and annulus are thickened and redundant (Figure 2). Sometimes the posterior annulus of the disc is redundant as well. These cause direct mechanical compression of the cauda equina leading to indirect vascular compromise of the spinal canal and nerve root inflammation. This condition occurs most often in patients in their 60s and 70s. The typical presentation is burning symmetric leg pain (claudication) when upright and relief when seated. Unlike disc herniations, the leg symptoms are symmetric. Unlike spondylolisthesis, there is minimal back pain, and unlike vasogenic claudication, no physical exertion is required for claudication to arise; simply standing in place for a few minutes produces leg pain.

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