Spinal stenosis—the narrowing of the spinal bone channel— has been a recognized diagnosis, particularly in patients over the age of 50, for approximately 180 years, but due to the difficulty of studying the congenital or patho-mechanic phenomenon in subjects (many of whom remain asymptomatic in the beginning stages of the disease), there is still no exact definition of the disorder. It appears men are more susceptible than women to spinal stenosis, except in the manifestation of degenerative spondylolisthesis, which occurs more often in women.
Although many studies have established the relationship between extension and flexion on the diameter of the spinal canal and dural sac cross-sectional area (DCSA), the effect of axial loading during the standing position or when using a compression device is less understood. This is in part due to the increased risk to study subjects when using ionizing radiation and invasive contrast injections of myelography and the relative unavailability and expense of open MRI systems, which allow examination of study subjects in the upright, vertical position.
The development of devices that allow simulated compression and axial loading on subjects during horizontal MRI’s have aided in recent research, and one study concluded that inducing compression of roughly 50 percent of a supine subject’s body weight during MRI simulates the condition and effects of an upright standing position. A new study 1 hypothesized that applied simulated lumbar lordosis and axial compression were both necessary to achieve the effects of standing in horizontal MRI study subjects.
In this study, 36 patients with lumbar spinal stenosis involving narrowing of the spinal canal (central spinal stenosis) presenting as neurogenic claudication, concluded that extension—not axial compression—was the dominant cause in the reduction of DCSA. Spinal canal diameters were not affected in any meaningful way by the application of axial loads in the study subjects.
The results of the study suggest that the diagnosis of central spinal stenosis is achievable through horizontal MRI machines when the patient is placed in a straight-legged, supine posture using a lumbar pillow to create a lumbar lordosis that simulates a standing position.