This common association of leg pain with upright position is likely a matter of simple mechanics. The ligamentum flavum forms part of the posterior border of the spinal canal. In extension, this ligament bulges more, much like a relaxed rubber band. When patients with stenosis are upright, this ligament becomes thicker and redundant, leading to increased compression of the nerves in the, leading to increased compression of the nerves in the spine. Conversely, sitting flexes the spine, causing the ligament to be stretched slightly thinner, and relieving nerve pressure and leg pain. Lumbar stenosis patients are also more comfortable standing or walking when bent forward, such as over a shopping cart. Both of these positions flex the spine.
Conservative management can include physical therapy to increase abdominal tone and reduce the lumbar curve. For the same reason, weight loss can be effective in some patients, if sufficient abdominal girth is reduced. Abdominal weight can exacerbate the symptoms of stenosis. A large abdomen shifts the center of gravity forward. To stand upright, these overweight patients must compensate by arching the back even more. Consider how a pregnant woman stands.
Relief of leg symptoms can often be obtained with epidural steroid injections. Steroids can reduce the inflammation of the compressed cauda equine, potentially allowing delay of surgical treatment for months or longer if patients are successful in making the other recommended changes to their posture and weight. Up to three injections can be given safely in any 12-month period, and some patients obtain months of relief with a single injection.
Eventually, however, conservative measures may not be able to overcome what is a progressive degenerative process. The surgical alternative is decompressive laminectomy. This operation involves removal of a portion of lamina and the underlying ligamentum flavum (Figure 3) to re-expand the spinal canal. This simple operation has been performed in some manner since at least the 1920s. By all accounts, it has been an impressively successful and cost-effective treatment, both in the U.S. and around the world. It requires nothing in the way of implanted metal, bone graft material, fusion healing or navigational technology. And the long-term outcome? About 90% of well-selected patients improve, with a major complication rate of less than 2% and a minor complication rate of 5%.
Despite this historical success, new devices and procedures have been developed to treat this condition, promising faster surgery, safer surgery or more permanent results, albeit at higher cost. One device, the X-STOP, is a metallic spacer placed between the dorsal spinous processes. Because it can be placed in an outpatient setting, it is cost-effective for single-level stenosis, but only when compared with the high cost of inpatient care in developed countries. Unfortunately, the high cost of the device itself negates its cost effectiveness when treating more than one level. There have also been questions about the longevity of effect and complications, which include spinous process fractures, new onset radiculopathy and a high reoperation rate in one recent series.6