Data from a recent study found that vertebral body tethering had little effect after the initial correction for scoliosis patients.

New data from patients across North America has raised questions about the effectiveness of vertebral body tethering for scoliosis.

The study, led by Lindsay Andras, MD, associate division chief and director of the Spine Program at the Jackie and Gene Autry Orthopedic Center at Children’s Hospital Los Angeles, found that 92% of patients who underwent tethering surgery did not experience a further postoperative decrease in major Cobb angle (a measure of the spine’s curve).

“There has been a lot of excitement about tethering, but unfortunately, the press got a little ahead of the science,” said Andras. “These findings shine a light on the fact that we’re still very much in the learning phase of this procedure.”

Vertebral body tethering (VBT) is a newer surgical option for adolescent idiopathic scoliosis. Approved by the Food and Drug Administration in 2019, VBT uses a system of metal anchors and a flexible cord, called a tether, to straighten the spine.

While the initial tethering surgery achieves significant curve correction, the idea is for the tether to cause additional, gradual straightening as the child grows. However, prior studies have shown mixed results, with some suggesting that the guided growth is minimal.

So far, the studies have looked at overall averages, not individual results.

“We know that the mean does not tell the whole story,” said Andras. “The purpose of our research was to be more granular—to look at exactly how much change in curve is seen after the tether is initially placed.”

To do this, Andras examined data from the Pediatric Spine Study Group, an international consortium of pediatric research centers. The data included 113 children and adolescents who underwent tethering for idiopathic scoliosis at institutions across the US and Canada.

The team then tracked the change in each patient’s major Cobb angle—from the first standing X-ray after tethering surgery until the final follow-up visit two to four years later.

At the final follow-up, the study found that:

  • In 50% of patients, the major Cobb angle was unchanged compared with their first standing X-ray after surgery. The curve had not further corrected as planned, but it had not worsened.
  • In 40% of patients, the curve had worsened by more than 5 degrees.
  • Only 8%—a total of nine patients—had more than 5 degrees of additional curve decrease. However, two of those patients overcorrected and needed a second surgery to release the tether.
  • Some orthopedic surgeons argue that patients undergo VBT too late when they don’t have enough growth potential left. The tether is designed to straighten the spine further as the child grows. If this growth does not occur, the straightening will not occur.

However, Andras notes that 90% of the patients in her study underwent VBT while they were still growing, with their skeletal maturity at or before Risser stage 2 when the growth rate slows.

“Even in this younger group, we’re not seeing VBT perform reliably,” said Andras. “It’s possible that patients need to be even younger. But whether it’s indication, technique, or technology, it’s clear we don’t have this procedure figured out yet.”

Another concern from current data is that the long-term results still need to be discovered.

“This data shows that most patients are left with some curve remaining,” said Andras. “What do those curves do over time? What happens after 10 years? 30 years? We don’t know.”

To better understand those implications, she and her team are now investigating what happens to patients whose tethers break—a common occurrence.

“We are still working to try to achieve comparable outcomes with VBT, but we have a long way to go in refining this approach,” she explains.

Photo 70468831 © Katarzyna Bialasiewicz |