Non-fusion surgeries for scoliosis are gaining popularity with patients and their parents as a motion-sparing alternative to traditional scoliosis fusion surgery. Two of these procedures (VBT and ApiFix) have been “CE mark” approved in Europe and used “off label” for years in the United States, but recently received FDA HDE approval for both devices, paving the way for careful and selective usage.
This rapid pace of advancement has left many parents and patients confused and unable to discern which of the fusionless surgical procedures may be most beneficial for early stage growth patients with progressive scoliosis.
The goal of this article is to compare and contrast vertebral body tethering and the MID-C system by ApiFix in a clear and simple manner.
Vertebral Body Tethering (VBT)
VBT is a motion-sparing non-fusion surgical procedure in which anterior surgical screws are inserted into the vertebral bodies (through relatively small incisions in the chest cavity) along the outside of the curvature, with a tether/cord run through the screws and tightened. The tightening of the tether causes a straightening of the spine and allows for additional spinal growth. The vertebral body screws can be placed to reduce spinal rotation with remaining growth, but with only moderate impact on existing rib cage rotation.
MID-C (Minimally Invasive Deformity Correction) by ApiFix
ApiFix is a posterior (back) fixed device with an internal ratchet system that will distract (stretch) the inside part of the curve open, thus reducing the spinal curvature. It does not de-rotate the spinal curvature. While the intersegmental range of motion covered by the device is limited, the device does include a novel poly-axial joint system that allows the patient to retain significantly greater spinal motion than with a traditional short fusion of the area.
VBT & ApiFix Comparison
- FDA-approved device
- Recommended for patients with early stage growth (risser 0–2)
- Significant curve flexibility required
- 75% curve correction (on average)
- Recommended for thoracic curve patterns only
- Curve sizes 35–60 degrees
- Multiple surgical implants and hardware
- Limits range of motion approximately 20%
- Improves lateral bending (Cobb angle) and spinal rotation
- FDA-approved device
- Recommended for very early stage growth patients (risser 0–1)
- Extreme curve flexibility required
- 35% curve correction (on average)
- Recommended for thoracic or thoraco-lumbar curve patterns
- Curve sizes 40–65 degrees
- Only 2–4 posterior screw attachments
- Limits range of motion approximately 40%
- Improves lateral bending (Cobb angle) only
Both ApiFix and Vertebral Body Tethering are becoming mainstream treatment options for patients with progressive scoliosis who have the majority of their growth remaining.
Far less invasive than traditional spinal fusion surgeries, these procedures and devices can be used to “guide” remaining growth and limit spinal deformity. The motion-sparing aspects of these newer surgical approaches should prevent much of the stress on the unfused spinal segments that are susceptible to degeneration with fusion surgeries. Minimized blood loss and smaller surgical entry points also reduce the risk of infection, hospitalization, and recovery times.
VBT (available for double curve patterns) and ApiFix (recommended for patients with single curve patterns only), risser 0–2, and excellent curve flexibility (bends to 30 degrees or less on a lateral fulcrum bending x-ray).
Multiple patients have been able to increase curve flexibility with the ScoliSMART BootCamp program, which can be a vital resource for parents and patients seeking VBT or ApiFix procedures but do not currently qualify due to the curve apex flexibility requirements. Research is currently underway to determine the program’s effectiveness as a viable VBT or ApiFix preparation program option.
“Fusion-free” devices for scoliosis surgery definitely seem to be the future innovation for moderate to severe scoliosis cases not responding to conservative treatments and that are likely to experience growth-spurt related progression. Less invasive, more motion-sparing, and faster recovery times are welcome features over traditional scoliosis fusion procedures. Long-term follow up studies still need to be conducted to determine the rate of complications and effectiveness over the course of a normal lifespan.