Epidemiology of Lumbar Spinal Stenosis

Epidemiology data on lumbar spinal stenosis come from several studies.  The annual incidence of spinal stenosis observed in a Swedish study that defined spinal stenosis as a canal of 11 mm or less among patients referred to orthopedic departments was approximately 5 per 100,000 inhabitants (Johnsson, 1995).

In the National Low Back Pain Study (Long, BenDebba, Torgerson et al., 1996), records were examined for 2,374 patients with chronic low back pain.  These patients sought help from orthopedic surgeons and neurosurgeons at eight academic medical centers across the United States from 1986 to 1991.  Of these patients, 45.8 percent were male and 54.2 percent were female, with a mean age of 45.3 years (standard deviation 12.79, range 25 to 75).  The proportions and categories diagnosed were 62 percent root compression, 19.6 percent myofascial syndrome, 18.7 percent instability, 2.1 percent postsurgical complications, and 19.1 percent other (see Table 1).  Within the broad category of root compression, the final diagnoses were 59.2 percent herniated disk, 22.6 percent spinal stenosis, 19.7 percent lumbar spondylosis, 14.0 percent osteoarthritic root compression, and 9.8 percent nonherniated degenerated disk.  In other words, 69 percent of root compressions were disk-related, and 57 percent were osteo-related (26 percent were both, so these percentages sum to 126 percent).  Within the broad category of instability, the final diagnoses were 39.1 percent spondylolisthesis, 25.7 percent facet joint arthritis, 19.3 percent lumbar instability, 16.6 percent spondylolysis, 10.2 percent compression fracture, and 2.7 percent spina bifida.  For patients with root compression, 54.5 percent were given conservative care, 30.4 percent were given surgery, and 13.3 percent were given no treatment.  For those with instability, 70.6 percent were given conservative care, 15.3 percent were given surgery, and 14.1 percent were given no treatment.

From the above data, we calculate that of all of these patients seeking treatment for low back problems, 35 percent had osteo-related root compression and were possible candidates for bone-removing surgery (62 percent had root compression, and 57 percent of these had osteo-related compression: 23 percent spinal stenosis, 20 percent lumbar spondylosis, 14 percent osteoarthritic root compression).  However, the severity of disease was not reported; thus, the proportion of these patients with disease severe enough to indicate surgery is not known.

The National Ambulatory Medical Care Survey (NAMCS) also provides data on the incidence of lumbar spinal stenosis in the US population (Hart, Deyo, and Cherkin, 1995).  The NAMCS is an annual survey of 3,000 general physicians conducted by the National Center for Health Statistics and is intended to be representative of practicing, nongovernmental, office-based physicians in the United States.  Over the period 1989 to 1990, the diagnostic cluster for low back pain ranked fifth in frequency among categories and accounted for 2.8 percent of patient visits.  Only visits for hypertension, pregnancy, general medical exam, and acute upper respiratory infection ranked higher in frequency of reasons for visiting a physician.  The survey estimated that 29,964,894 visits for mechanical back problems were made in the United States during this period.  Of these visits, 56.8 percent were classified as nonspecific backache, 11.1 percent as herniated disk, and 3.9 percent as spinal stenosis.  For the purposes of analyzing survey data, spinal stenosis was defined as lumbar stenosis or spondylogenic compression of the lumbar spinal cord or nerve roots.

The National Spine Network (NSN) provides another estimate of the prevalence of lumbar spinal stenosis (Fanuele, Birkmeyer, Abdu et al., 2000).  Data on 17,774 patients from 25 centers that treat back and neck problems were examined in this study.  The average patient age was 47.5 years (SD 15.4, range 17 to 98), 54.7 percent of patients were male, and 84.2 percent of patients were white.  Among these patients, 13.1 percent were specifically diagnosed with spinal stenosis, 12.9 percent with degenerative spondylosis due to aging, and 19.2 percent with herniated disks.

A comparison of the data from these three studies indicates that among patients with low back pain who see a specialist, 13 percent to 14 percent may have spinal stenosis.  These surveys also indicate that among patients with low back pain who see a general physician, 3 percent to 4 percent may have spinal stenosis (see Table 2).  The NAMCS estimate of 3.9 percent of backache patients having lumbar spinal stenosis is probably the more reliable because this patient base comes from office-based physicians in the United States.

In regard to spondylolisthesis, in lateral radiographs taken for the longitudinal Framingham Heart Study (Kauppila, Eustace, Kiel et al., 1998), 1 percent (2/219) of men and 1.5 percent (6/400) women already had slippage at the baseline measurement at the mean age of 54 years. Over the following 25 years, 11 percent (23/217) of men and 25 percent (100/400) of women developed degenerative vertebral slippage (see Table 3).

There are many etiologies for chronic low back pain, of which lumbar spinal stenosis is just one.  Figure 1 provides a differential diagnosis that separates the typical symptoms of lumbar spinal stenosis from other potential causes of low back pain.