What is a lumbar discectomy?

Ok, so at this point all of you know the difference between a bulging and herniated disc.  Ultimately, as we discussed in our last post, the semantics matter less than the fact that either of these conditions can compress a nerve root and cause severe pain, numbness or weakness.  In order to relieve the pressure caused by the bulging or herniated disc a spine surgeon may offer a lumbar discectomy.  

The term discectomy is actually a bit of a misnomer with its suffix –ectomy, meaning to remove.  This term thus implies that the surgeon removes the entire intervertebral disc (IVD).  In fact, in a lumbar discectomy only a small portion, the bulging or herniated portion, of the IVD is removed.

A lumbar discectomy is by no means a mandatory procedure and a trial of non-surgical treatments should be considered prior to surgery.  A large study called the Spine Patients Outcomes Research Trial (SPORT) began enrolling patients in 2000 to try to establish whether surgical treatments were better than non-surgical treatments for some common degenerative spinal conditions.  In 2006 the SPORT authors published a randomized controlled trial of lumbar discectomy versus non-surgical treatment for lumbar disc herniation.   While the study’s methodology was flawed, it was able to illustrate some interesting points about patients with herniated discs.  First, with time, patients improved regardless of which treatment group they were in.  Thus, as long he or she can tolerate it, I typically will encourage a patient with a herniated disc to try a course of non-surgical treatment, including physical therapy, chiropractic manipulation or epidural steroid injections. These therapies buy the patient time while the body heals itself and in many cases the herniated disc fragment is absorbed by the body (contrary to popular belief, no matter what your chiropractor says, the fragment does NOT go back into the disc space.)  While SPORT clearly showed that a trial of non-surgical treatment is a reasonable option, it also showed that patients who underwent surgery for their herniated disc got better faster.  Surgical patients also had improved physical function and had higher satisfaction with their treatment than non-surgical patients.  One of the criticisms of SPORT is that patients with the most severe symptoms could choose surgery immediately rather than being randomized into the study.  This, of course, biases the study in that by eliminating the worst patients from analysis it appears that surgical and non-surgical treatments are more equivalent than they really are.  Ultimately, I interpret SPORT like this: if the patient has mild to moderate symptoms that they are tolerating reasonably well then non-surgical treatments like physical therapy will probably be just fine for them and they can avoid surgery. Patients with severe symptoms, especially if they have weakness (i.e. footdrop), are probably going to recover faster and more fully with surgery.  The speed of recovery is not an insignificant factor for someone who, say, has to miss a lot of work because of his symptoms.  Surgery helps patients like this get back to work and normal life more rapidly. 

Classically, lumbar discectomy (first described in the late 1920s) was performed via long midline incisions.  As we’ve discussed in previous posts these incisions can be quite destructive.  Recently, minimally-invasive techniques were developed to help mitigate some of the problems associated with these midline incisions.  When I perform lumbar discectomy I will make an 18mm incision just off of midline centered over the disc space in question (for an “L4/5” herniation this is the disc space between the 4th and 5th lumbar vertebrae.)  I’ll then use a series of tubular dilators to gently dilate the muscle before a tubular retractor is inserted.  Using an operative microscope, I can perform the entire operation through this small corridor and in turn can avoid damaging the supporting structures of the spine.  Once at the spine I have to drill a small opening through the lamina (a laminotomy) to get into the spinal canal (see figure 1.)  After removing a non-essential ligament, the ligamentum flavum, I’m able to visualize the thecal sac (fluid-filled sac which contains the nerves of the cauda equina) and compressed nerve root.  I then gently move the nerve out of way and can get to the offending piece of disc.  In the case of a herniated disc (a.k.a. a free fragment) the fragment is typically sitting there under the nerve ready to be plucked out.  In the case of a bulging disc (a.k.a. a contained fragment) I have to make a cut in the annulus (an annulotomy) in order to remove the fragments of NP.  After I remove all of the offending pieces of disc I’ll confirm that the nerve is completely decompressed and then will close the incision.  Patients go home immediately after the procedure. Please see the video at the end of the post to see all of these steps during an actual lumbar discectomy. 

SpineLumbar4 5

Figure 1. Orange oval indicates area of bone removed in laminotomy done to gain access to a right L4/5 disc herniation. 

I typically don’t talk about risks of surgeries in this post but it is worth mentioning one risk of lumbar discectomy.  I always tell my patients that for the first two weeks they should do nothing but walk and should avoid any heavy lifting or bending.  This is because for the first few weeks after surgery they are at higher risk of reherniating another disc fragment (I quote a 10% overall risk.)  After the initial fragment is remove the hole in the annulus through which it herniated is still open and takes some time to scar in and close up.  If the patient isn’t careful a new piece can herniate and they’ll be right back where they started.   Surgeons have tried using sutures or small stapling devices to close the annular defect.  Unfortunately this has never been shown to reduce the risk of reherniation so most surgeons leave the defect to heal naturally and advise their patients to be careful in the first few weeks after surgery.  

In our next post we’ll discuss a variation of lumbar discectomy, the far-lateral discectomy.  

Thanks for reading!

J. Alex Thomas, M.D.

Sources:

Weinstein JN, Tosteson TD, Lurie JD, Tosteson ANA, Hanscom B, Skinner JS, et al.: Surgical vs Nonoperative Treatment for Lumbar Disk Herniation: The Spine Patient Outcomes Research Trial (SPORT): A Randomized Trial. JAMA 296:2441–2450, 2006.

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