In our last post we discussed how lumbar stenosis, or narrowing of the lumbar spinal canal, causes a painful condition called neurogenic claudication. Patients with this condition report that they can only walk so far or stand for so long before they experience burning pain in their buttocks and legs requiring them to sit and rest. While all patients should undergo a course of conservative therapy for lumbar stenosis (i.e. physical therapy or epidural steroid injections), ultimately stenosis is a structural problem that is best treated with surgery. The surgical treatment of lumbar stenosis is a lumbar laminectomy.
Figure 1: Image on left demonstrates the elements of the posterior aspect (rear) of the spine. The pink arrow indicates the lamina, the green arrow indicates the spinous process and the blue arrow indicates the facet joint. These structures are also seen on the normal axial MRI on the right.
If you consider the spinal canal to be a bony tunnel, the lamina is the bony roof of the tunnel (see figure 1). The suffix –ectomy is derived from Greek origins meaning “to cut out” (everyone has heard of an appendECTOMY.) Thus, a laminectomy literally means the cutting out of the lamina. The lamina itself is rarely the cause of stenosis. The lamina must be removed, however, so that the surgeon can access the buckled ligamentum flavum and overgrown facet joints that typically cause stenosis. These structures are then removed in order to decompress the thecal sac (a sac filled with cerebrospinal fluid, CSF, and the nerve roots of the cauda equina) and relieve the stenosis.
Traditionally a laminectomy is done via a long midline incision. These midline incisions can be quite destructive, however, as they require removal of the spinous process, interspinous ligament and other important structures that support the healthy spinal segments above or below the area of stenosis (see figure 2.)
Figure 2: Traditional midline incision for laminectomy. Notice that the spinous process has been removed along with the lamina to expose the thecal sac. Also note that normal levels above and below must be exposed and may be damaged in the process.
Rather than using a long midline incision, I perform a minimally-invasive laminectomy using paramedian (off midline) incisions and special tubular retractors to spare the healthy muscles and ligaments of spine (see video 1.) Once I’ve docked the tubular retractor I use a high-speed drill to drill away the lamina as well as parts of the overgrown facet joints. This then exposes the underlying ligamentum flavum which is then removed using small instruments called curettes and Kerrison rongeurs. Removal of the ligamentum flavum is typically adequate to decompress the dura of the thecal sac to relieve the stenosis (see video 2). Occasionally a foraminotomy is also performed to decompress a single nerve root as it leaves the spinal canal (this will be discussed in a later post.) While the incision is made on one side of the spine I can angle the tubular retractor across midline to undercut the spinous process and decompress the opposite side of the spinal canal as well (see figure 3.) Thus, in my hands a bilateral two-level laminectomy can be performed through a single 18mm incision. These tiny incisions allow for less pain, faster recovery and shorter hospital stay (my patients who undergo one- or two-level minimally-invasive laminectomies typically go home the same day) when compared to traditional laminectomy (see figure 4.)
Video 1: Dilation and docking of tubular retractors for lumbar spine surgery.
Figure 3: Using the tubular retractors to decompress both sides of the spinal canal via one incision. Source: Palmer et al.
Figure 4: Pre- (left) and post-operative (right) MRI demonstrating the results of minimally-invasive lumbar laminectomy. Notice the increase in diameter of the spinal canal after decompression (outlined in blue.) Source: Alimi et al.
Again, because lumbar stenosis is a structural problem I feel that it is best treated with surgery. This isn’t just my opinion though: lumbar laminectomy has been proven superior in the literature as a treatment of lumbar stenosis when compared to non-operative treatment. In a landmark trial published in the New England Journal of Medicine in 2008 Weinstein et al followed 654 patients with lumbar stenosis who were treated with surgery or nonsurgical “usual care” of physical therapy, steroid injection, etc. The patients who underwent surgery had significant improvement in pain levels and function when compared to nonsurgical patients. The benefits of surgery were long-lasting and persisted through the two-year follow up period of the study. Randomized trials such as this one, especially ones that clearly support surgical intervention versus conservative therapy, are almost unheard of in neurosurgery. Thus, when a patient comes to my office with severe neurogenic claudication caused by lumbar stenosis I won’t waste too much time on conservative therapy before recommending surgery.
Thanks for reading!
J. Alex Thomas, M.D.
Video 2: Intraoperative video of lumbar laminectomy (with foraminotomy.)
Alimi, M., Hofstetter, C. P., Pyo, S. Y., & Paulo, D. (2015). Minimally invasive laminectomy for lumbar spinal stenosis in patients with and without preoperative spondylolisthesis: clinical outcome and reoperation rates. Journal of Neurosurgery. Spine, 22(April), 339–352.
Palmer, S., & Davison, L. (2012). Minimally invasive surgical treatment of lumbar spinal stenosis: Two-year follow-up in 54 patients. Surgical Neurology International.
Weinstein, J. N., Tosteson, T. D., Lurie, J. D., Tosteson, A. N. a, Blood, E., Hanscom, B., … An, H. (2008). Surgical versus nonsurgical therapy for lumbar spinal stenosis. The SPORT Authors. The New England Journal of Medicine, 358(8), 794–810.