Spinal stenosis is a narrowing of the vertebral canal that compresses spinal nerves and may cause back and leg pain and difficulty walking. Lumbar spinal stenosis is one of the most common degenerative conditions of the spine and is the most common reason for lumbar spine surgery on the elderly (Weinstein, Tosteson, et al., 2008). Treatment of spinal stenosis may involve nonsurgical care, decompression surgery (involving the removal of bone and ligaments around the stenosis), or spinal fusion surgery (with or without the use of implants).
Rates of spinal surgery increased dramatically in the Medicare population between 1992 and 2003 (Tosteson, Skinner, et al., 2008), and nearly $20 billion is spent annually on these procedures. Between 1980 and 2000, surgery for spinal stenosis was the fastest-growing type of lumbar surgery in the United States (Deyo, Mirza, et al., 2010). Rates of spinal stenosis surgery vary by more than a factor of five across geographic regions, raising concerns that many of these procedures may be inappropriate (Weinstein, Tosteson, et al., 2008).
Between 2002 and 2007, the overall rate of lumbar spinal stenosis surgery decreased slightly in the Medicare population, but the proportion of surgeries involving complex fusion procedures increased fifteenfold (Deyo, Mirza, et al., 2010). This increase follows an overall trend dating back to 1996, when the FDA first approved the use of intervertebral fusion cages (Deyo, Gray, et al., 2005). The rate of spinal fusion surgery increased 77 percent between 1996 and 2001, while the rates of other orthopedic surgical procedures increased modestly (e.g., the rate of knee and hip arthroplasty increased 13 to 14 percent) (Deyo, Nachemson, et al., 2004). However, as of 2001, the greatest growth in lumbar fusion surgery was for the treatment of herniated discs rather than spinal stenosis (Deyo, Gray, et al., 2005).
The risks of spinal stenosis surgery may be relatively low, but the procedure is disproportionately performed on the elderly, who have somewhat higher risks due to comorbidity. Analysis of Medicare data suggests that 3.1 percent of spinal stenosis surgery patients experience major medical complications, and 30-day mortality rates are approximately 0.4 percent. Both rates increase with age (Deyo, Mirza, et al., 2010). Complex fusion operations are associated with a 5.2-percent rate of major medical complications, compared with 2.1 percent for decompression-only procedures. Mortality rates are twice as high with complex surgery (0.6 percent versus 0.3 percent), and patients undergoing complex fusion operations remain hospitalized for two additional days, on average.
Over time, improvements in surgical and anesthetic techniques and supportive care have probably lowered the risks of surgery (Deyo, Mirza, et al., 2010) and may have fueled growth in the volume of these procedures. Improvements in diagnostic imaging technology such as axial-spine imaging may also have contributed to this growth (Deyo, Nachemson, et al., 2004), because surgeons often rely on imaging for diagnosing spinal stenosis and for determining the appropriateness of surgery (Haig and Tomkins, 2010). New devices, including spinal-fixation devices, computer-guided and minimally invasive surgery, bone-graft substitutes, and supple-ments such as bone morphogenetic proteins, may also contribute to the increasing use of surgery (Deyo, Nachemson, et al., 2004). No RCTs or prospective-cohort studies existed at the time intervertebral fusion cages were first approved for use (Deyo, Nachemson, et al., 2004).