Vertebral Body Tether of Lumbar Scoliosis Curves 11-30-2020
Over the last 15 years there has been an increasing interest from patients and families in non-fusion solutions for scoliosis. Vertebral Body Stapling (VBS) was the first non-fusion technique reported for treatment of idiopathic scoliosis, in the 1950s. Due to the lack of advance implant technology the technique disappeared for 40+ years, but re-appeared in the early 2000s when newer high-tech implants became available.
At the same time a parallel implant system, Vertebral Body Tethering, was also being developed. Due to the ability to exert a stronger correction force to the spine VBT gained traction, since it can treat curves up to 60 degrees. In comparison, VBS failed to maintain traction, mainly due to its lower correction force and its application only in smaller scoliosis curves (35 degrees). Over time VBS faded, and at present there are no commercially available implants in the U.S. to perform VBS.
Many studies from around the world have reported on VBT, but most have focused on its application in the thoracic spine.
Thoracic spine (in blue) and lumbar spine (in pink)
Though the thoracic spine has some intervertebral motion, the lumbar spine has vastly more motion at each intervertebral disc. Conceptually it makes sense that VBT would have a greater impact on preserving spine motion, than fusion, in the lumbar spine. So why have pediatric spine deformity surgeons focused on the application of VBT in the thoracic spine, if there may be less benefit than the lumbar spine?
Two reasons for this are:
1. The surgical approach to the thoracic spine can be accomplished with a minimal number and length of surgical incisions, due to the use of a thoracoscope (camera inserted into the chest through small incision to view the spine through the chest). This is obviously attractive as it leaves small aesthetically reasonable scars. Surgeons with experience in thoracoscopic spine surgery (VBS and fusions) have considerable expertise with this approach and area of the spine.
2. The most common curve patterns seen in idiopathic scoliosis are in the thoracic spine. So surgeons are seeing much more scoliosis in the thoracic spine than the lumbar spine.
So what do we know about the use of VBT in the lumbar spine? Overall not very much.
There are only two studies, published in 2020, which specifically report the use of VBT in the lumbar spine. There are 6 important points of these 2 studies:
1. 1. Both of these are early-outcome studies with a minimum follow-up after surgery of 2 years and a mean follow-up in both studies of approximately 3 years. This is very short follow-up for patients who will live another 60+ years. There is no long-term data on VBT. What will happen long-term to the lumbar spines with a tether placed across the discs? Will they become arthritic? Will they cause pain?
2. 2. Combined they report only on 9 lumbar curves, as opposed to the thoracic spine which have 100s of cases reported in the literature.
3. 3. Tether breakage in 47-48% of all patients (thoracic and lumbar)
4. 4. Success rates of 53-74%
5. 5. Reoperation rates of 21-24% (1 patient out of 5 underwent a repeat surgery)
6. 6. VBT should only be done in patients with growth remaining. It is not indicated in skeletally-mature patients (Sanders 7-8 or Risser 4-5)
In contrast to these VBT data, lumbar fusion surgeries for scoliosis have a long history, a high rate of success and low frequency of reoperations.
Picture credit: https://whyy.org/segments/rope-or-rod-torn-between-scoliosis-surgeries/
So which way should you go? Lumbar VBT or Lumbar fusion surgery?
There are many factors which can go into the decision-making process of informed consent and should be discussed in detail with a surgeon who has experience in both approaches. So I can’t tell you which surgery you or your child should have.
If motion preservation is an important aspect of scoliosis surgical treatment to you, then it is imperative you are fully informed as to the alternatives, benefits, complications and risks of VBT. No surgery is without risks and potential complications. If you fully understand the above-mentioned data, then VBT may be a reasonable procedure for lumbar scoliosis in you or your growing child.
VBT holds significant promise. I personally believe that VBT, or some variant of it, which can preserve spine motion and correct scoliosis will be eventually be highly successful with long-term outcomes. However until that time, caveat emptor or “let the buyer beware".
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