I’m back! I realize there’s been quite a delay since my last post and for that I apologize. For over a year now I’ve been busy helping to develop a new retractor system for lumbar spine surgery. This retractor allows surgeons to perform an anterior lumbar interbody fusion (ALIF) in the lateral position, a procedure we (perhaps not so creatively) call lateral ALIF (see figure 1). Why does that matter? In my opinion, an ALIF is the most powerful way to fuse a segment of the lumbar spine and correct spinal deformity (hint: it’s because ALIF allows you to insert the largest spacers!). One drawback of ALIF, though, is that since it’s traditionally performed in the supine position (with the patient laying on his back), if the surgeon wishes to place posterior instrumentation he has to close the incision on the front of the patient and then reposition the patient prone to get access to the back of the spine. This process of repositioning can add nearly an hour of time to the procedure and may also increase risk to the patient. By keeping the patient on his side, in a single position, the surgeon can harness the power of ALIF and then immediately be ready to place posterior instrumentation, all without having to stop to reposition the patient (see figure 2). Now, a so-called 360-degree lumbar fusion that used to take 3 hours to perform can now be done in an hour. This is good for my OR throughput but it’s GREAT for you, the patient, who will avoid that extra time under anesthesia. This could potentially be the one of the most important innovations in spine surgery in years.
Figure 1: The new Lateral ALIF retractor during a recent ALIF at L5/S1. The patient is in the lateral decubitus position with their left side up. The patient’s head is at the left of the image.
Figure 2: Lateral ALIF at L5/S1. This image gives you an idea of the massive increase in efficiency you get without having to reposition the patient. Here, I’ve already placed wires for insertion of percutaneous pedicle screws while my physician assistant Jack Bagley continues to close the abdominal lateral ALIF incision. Patient is right side up with head towards the left of the image.
The ALIF, first described in the 1930s, is the original interbody fusion in which bone graft is inserted into the cleaned out intervertebral disc (IVD) space to promote fusion and correct spinal deformity (in modern ALIF the bone graft is carried in a spacer or cage). Since then, many other techniques have been developed to place spacers into the disc space via a posterior approach. These other –IF procedures, such as posterior lumbar interbody fusions (PLIFs) or transforaminal interbody fusions (TLIFs) represent early attempts at a single position strategy. These procedures allow surgeons to perform the three standard steps of a spinal fusion: 1) neural decompression (laminectomy or discectomy), 2) interbody fusion, and 3) placement of posterior instrumentation with the patient in the prone position. Thus, traditional spine surgeons may say “Well I’ve been doing ‘single-position’ lumbar fusions for years.” Indeed, TLIF and PLIF are the most common way to perform lumbar fusions these days. The problem with TLIF and PLIF, though, is that in order to place spacers from behind, one or more nerves have to be retracted out of the way to sneak the spacer into the disc space. That means that for PLIF and TLIF the surgeon is forced to use very small spacers (see figure 3). Because you’ve read recent Spinal (con)Fusion posts, though, you know that I believe in the power of large intervertebral spacers. Bigger is better and thus ALIF is a much more powerful technique for spinal fusion than PLIF or TLIF. Now, by doing the ALIF in the lateral position I can have concurrent access to the back of the patient to perform a decompression and place pedicle screws without “flipping” the patient.
Figure 3: side-by-side comparison of various intervertebral spacers. Notice how much larger the XLIF/ALIF spacer is versus the much smaller TLIF or PLIF spacers. Size matters!
As you can probably tell, I’m very excited about this new retractor and surgical technique (yes, I’m biased.) In future posts we’ll talk more about the details of a lateral ALIF procedure. You’ll also see how well lateral ALIF at L5/S1 compliments the extreme lateral interbody fusion (XLIF) at L4/5 and above. Lots more about single-position lateral surgery to come!
Thanks for reading!
J. Alex Thomas, M.D.