By Dr. M. Darryl Antonacci, MD, FACS, Institute for Spine & Scoliosis
Patients and families researching scoliosis surgery encounter three surgical approaches: Anterior Scoliosis Correction (ASC), Vertebral Body Tethering (VBT), and traditional metal-rod fusion. These procedures differ in how they correct the curve, whether they preserve spinal motion, and who qualifies for them. This guide explains each approach and the differences that matter most when weighing your options.
The Core Difference: Motion Preservation vs. Permanent Fusion
The most important distinction among the three procedures is what happens to the spine's ability to move after surgery.
- ASC corrects the curve using vertebral body screws connected by a strong, flexible cord. The spine is straightened and the correction is held without fusing any vertebrae, so the treated segments retain motion.
- VBT places a tether along the growing spine to guide correction gradually as the patient grows. It also avoids fusing vertebrae, but it depends on remaining skeletal growth to achieve correction over time.
- Metal-rod fusion permanently joins vertebrae into a single rigid segment using rods and screws. The curve is stabilized, but the fused portion of the spine no longer moves.
What Is Anterior Scoliosis Correction (ASC)?
ASC is a motion-preserving scoliosis surgery developed and refined by Drs. Antonacci, Betz, and Cuddihy. The spine is approached from the front and side through small incisions between the ribs, which avoids cutting through the large muscles of the back. Vertebral body screws are placed and connected with a strong, flexible cord, and the curve is corrected during the operation itself.
How does ASC correct scoliosis?
During ASC, the surgeon de-rotates and straightens the spine on the operating table, then holds the correction with the screw-and-cord construct. Because the cord is flexible rather than rigid, the corrected spine keeps its ability to bend and rotate. No vertebrae are fused. The correction achieved in surgery does not depend on future growth, which is a fundamental difference from VBT.
What are the unique benefits of ASC?
ASC combines immediate curve correction with motion preservation. The anterior approach avoids the muscle disruption associated with posterior metal-rod fusion. Because ASC does not rely on remaining growth, it can treat patients that VBT cannot, including skeletally mature adolescents and adults, and it can address larger curves. Published outcomes from the Institute for Spine & Scoliosis are available on our peer-reviewed data page, and case examples are shown in our before and after gallery.
How Does Vertebral Body Tethering (VBT) Compare with ASC?
VBT and ASC are sometimes confused because both are anterior, non-fusion procedures. The difference is mechanical and it determines who each procedure can help.
What is VBT and how does it work?
In VBT, a tether is anchored to the vertebral bodies along the curve. The tether slows growth on the convex side of the curve while the concave side continues to grow, so the spine gradually straightens as the child grows. Because VBT harnesses growth to achieve correction, it is designed for patients with significant skeletal growth remaining.
What are the key differences between ASC and VBT?
ASC corrects the curve in the operating room and does not depend on growth. VBT achieves much of its correction gradually through growth modulation. As a result, VBT candidacy is limited to skeletally immature patients with moderate curves, while ASC can treat skeletally mature patients, adults, and larger curves. For a detailed comparison, see VBT and ASC surgeries compared.
How Does Metal-Rod Fusion Compare with ASC and VBT?
Metal-rod fusion is the traditional surgical treatment for scoliosis and remains the most commonly performed scoliosis surgery. It corrects the curve by permanently fusing the vertebrae in the treated segment.
What are the trade-offs of metal-rod fusion?
Metal-rod fusion stabilizes the curve, but the fused segments permanently lose motion. Loss of motion in the fused segment transfers stress to the discs and joints above and below the fusion, which is associated with adjacent segment degeneration over time. For active patients, the loss of spinal flexibility can affect sports and daily activities. These trade-offs are the reason motion-preserving alternatives were developed. A full comparison is available at ASC vs. metal-rod fusion.
Who Is a Candidate for ASC, VBT, or Metal-Rod Fusion?
Candidacy depends on skeletal maturity, curve size and flexibility, and overall health. In general:
- VBT requires significant remaining skeletal growth, which limits it to younger, skeletally immature patients with moderate curves.
- ASC does not require remaining growth. Candidates include skeletally immature adolescents, skeletally mature adolescents, and adults, across a wider range of curve sizes than VBT can address. Learn more at who qualifies for ASC.
- Metal-rod fusion is offered broadly and is often presented as the default option, but many patients told they need metal-rod fusion are also candidates for motion-preserving correction with ASC.
Because candidacy is case-specific, the only way to know which options apply to you is an individual review of your imaging and history by surgeons experienced in motion-preserving techniques.
Recovery: What to Expect
Recovery varies by patient, procedure, and curve, so beware of one-size-fits-all timelines. As a general pattern, the anterior approaches used in ASC and VBT avoid the extensive back-muscle dissection of posterior metal-rod fusion, which supports earlier mobility. Patients recovering from metal-rod fusion must also wait for the bone fusion itself to heal before returning to full activity, a constraint that does not apply to non-fusion procedures. Your surgical team will give you a recovery plan specific to your case. First-person accounts of the process are collected in what the ASC journey is really like.
Risks and Benefits to Discuss with Your Surgeon
Every scoliosis surgery carries risk, and every option involves trade-offs.
- ASC: as with any anterior spine surgery, risks include those common to major surgery, plus device-related considerations. The benefit is immediate correction with preserved motion and no fusion.
- VBT: correction depends on growth, so outcomes are less predictable at the time of surgery, and tether-related complications can require revision. The benefit is a non-fusion option for young, growing patients.
- Metal-rod fusion: the correction is stable, but motion in the fused segment is permanently lost and adjacent segments bear additional stress over time.
Importantly, outcomes data for VBT does not describe ASC. The two procedures use different constructs and correction strategies, and studies of tethering populations should not be applied to ASC patients. Peer-reviewed publications on ASC by Drs. Antonacci, Betz, and Cuddihy are indexed on our peer-reviewed data page.
Frequently Asked Questions
Is ASC the same as VBT?
No. Both are anterior, non-fusion procedures, but VBT relies on remaining growth to gradually correct the curve, while ASC corrects the curve during surgery using vertebral body screws and a flexible cord. ASC can treat skeletally mature patients and adults; VBT cannot.
Does ASC use rods?
No. ASC uses a strong, flexible cord connecting vertebral body screws. Rigid rods are used in metal-rod fusion, not in ASC.
Can adults have ASC?
Yes. Because ASC does not depend on skeletal growth, adults and skeletally mature adolescents can be candidates. Candidacy is determined case by case.
Can scoliosis be cured?
Scoliosis is corrected, not cured. Surgical treatment reduces the curve and restores balance; the goal of motion-preserving surgery is to do so while keeping the spine flexible.
Have Your Case Reviewed
If you or your child has been told that metal-rod fusion is the only option, a motion-preserving alternative may be available. Submit your case for review by Dr. Antonacci and his team.
