FDA Clears First Spinal Tether Device for Idiopathic Scoliosis

Megan Brooks


August 16, 2019

The US Food and Drug Administration (FDA) has approved the first spinal tether device to correct idiopathic scoliosis in children and adolescents who fail to respond to conservative treatment options, such as external bracing.

The Tether Vertebral Body Tethering (VBT) System (Zimmer Biomet Spine) is intended to treat growing children and adolescents whose spinal curves are approaching or have reached the range where surgical treatment is an option, the FDA explains in a news release.

"For children and adolescent patients with idiopathic scoliosis that does not respond favorably to bracing, treatment options have been limited to fusion surgeries," Capt Raquel Peat, PhD, director, Office of Orthopedic Devices, FDA Center for Devices and Radiological Health, said in the release.

The Tether device is a "new treatment option that could improve quality of life for patients with idiopathic scoliosis," said Peat.

Baron Lonner, MD, chief of minimally invasive scoliosis surgery at the Mount Sinai Health System in New York City, welcomed the approval. The decision "finally recognizes" VBT as a "mainstream option for scoliosis treatment," he said in a news release.

Idiopathic scoliosis — a sideways curvature of the spine with unknown cause — is common in children. It is typically diagnosed between ages 10 to 18, although it may occur at a younger age.  

The standard treatments for idiopathic scoliosis among children and adolescents who are still growing are conservative, nonsurgical treatments such as external bracing to help correct the spinal curvature.

However, about 6800 people in the United States each year develop a progressive curvature of the spine that does not respond to bracing. In these individuals, spinal fusion surgery to permanently stabilize and correct the problem is often successful but may restrict motion of the spine and lead to long-term complications such as pain, arthritis, and future spinal deformities, requiring additional surgery, the FDA notes.

"Patients have become increasingly interested in nonfusion surgical options for treating scoliosis. With VBT, patients can maintain flexibility and function in a way one can't with spinal fusion, and the medical community is optimistic that VBT will contribute to less degenerative disc problems over the long-term as well," said Lonner.

The Tether system includes anchors and vertebral body screws that are placed into the same side of each vertebra in the curved section of the spine through an incision in the side of the chest. A flexible cord or "tether" is connected to the screws. Tension is applied to the tether during surgery to compress one side of the spine and partially correct the curve. Over time, the tether slows growth on the curved side of the spine and promotes growth on the opposite side, providing additional correction of the curve as the patient continues to grow, the FDA notes. 

The device is not intended to be removed unless problems, such as overcorrections, develop. Patients with the device undergo follow-up X-rays to track the spinal curvature and identify any potential problems that might require additional surgery to revise or remove the device. If the Tether fails to adequately correct the curvature, spinal fusion surgery is still possible.

As part of the approval process, the FDA reviewed clinical data from 57 patients who received the device. At 2 years, 43 patients had sufficient improvement of the curvature of their spines and did not need spinal fusion.

The most common serious adverse events included overcorrection of the curvature, tether breakage, and pneumothorax. General complications consistent with any spinal surgical procedure included pain, respiratory problems, nerve injuries, and bleeding.

Zimmer Biomet Spine will partner with a group of surgeons who specialize in treating children and adolescents with spinal deformities to develop a patient data registry to help assess the long-term performance of the Tether system.

"The FDA continues to collaborate with stakeholders to encourage the development of registries, including the one being developed for this device, as an additional tool to gather and track real-world evidence," FDA Principal Deputy Commissioner Amy Abernethy, MD, PhD, said in the news release.

"This type of post-market data generation can provide ongoing device safety surveillance and additional evidence for effectiveness. More broadly, real-world evidence can help support innovative developments while ensuring that patient health and safety remains the top priority," she added.

The FDA approved the Tether device through its humanitarian device exemption pathway. Devices can be designated a humanitarian device if they treat or diagnose a condition affecting fewer than 8000 Americans each year.

Follow Medscape on Facebook, Twitter, Instagram, and YouTube.


Comments on Medscape are moderated and should be professional in tone and on topic. You must declare any conflicts of interest related to your comments and responses. Please see our Commenting Guide for further information. We reserve the right to remove posts at our sole discretion.