Anterior vertebral body tethering in progressive scoliosis has been extensively studied for its use in spinal correction of the main tethered curve over time. But, say a group of researchers from 12 institutions, there is a gap in the literature regarding the response of the uninstrumented, compensatory curves after initial implantation and during the follow-on period of growth modulation.
Their work, “Spontaneous Lumbar Curve Correction Following Vertebral Body Tethering of Main Thoracic Curves,” was published in the September 21, 2022, edition of The Journal of Bone and Joint Surgery.
Co-author Peter O. Newton, M.D., chief of the Division of Orthopedics & Scoliosis as well as surgeon-in-chief at Rady Children’s Hospital-San Diego, told OTW, “There have been a number of recent articles on the overall outcomes of vertebral body tethering and some now in comparison to posterior spinal fusion.”
“The specific question on response of the lumbar curve with treatment/correction of the thoracic curve is one that we have studied extensively with fusion, and this has led to limiting the fusion to just the thoracic curves for many patients, the so called, selective thoracic fusion for patients with thoracic and lumbar curves. Whether selective thoracic correction with vertebral body tethering will result in similar spontaneous lumbar curve correction is an important question this paper sought to address.”
Newton and his team pulled together data from 218 patients who had been treated with vertebral body tethering. The research team documented that the thoracic curve correction was 40% at the first-erect visit and 43% at 2 years. Lumbar correction was 30%, 26%, and 18% at the first-erect visit and minimally changed at 31%, 26%, and 24% at 2 years for lumbar modifiers A, B, and C, respectively.
A total of 118 patients (54%) had thoracic curve improvement between the first-erect and 2-year visits.
Suken A. Shah, M.D. vice chair of the Department of Orthopaedics and division chief of the Spine & Scoliosis Center at Nemours Children’s Hospital in Delaware, explained the importance of these results to OTW. “In very simple terms, the lumbar curve decreased on its own in patients who had flexible tethering of their thoracic scoliosis (the curve above). This phenomenon is seen in fusion surgery for scoliosis also, but since the correction potential in tethering is initially less than fusion instrumentation, the lumbar response is less robust. However, if the correction improves with growth and time (modulated by the tether), then the lumbar correction also gets better.”
We asked Dr. Newton how he interpreted the study results and he said, “Maybe not surprised as much as disappointed. Thoracic curve response to tethering remains quite variable from one patient to the next.”
“Identifying the ideal patients for thoracic tethering remains an area of active investigation. These findings may limit the number of patients who receive a tether of both their thoracic and lumbar curves now knowing the lumbar curve can correct on its own in response to thoracic curve correction following thoracic curve tethering.”
Primary author Burt Yaszay, M.D., professor and vice chair of the Department of Orthopaedics and Sports Medicine at the University of Washington School of Medicine, told OTW, “Current literature suggests that the correction of the thoracic curve following vertebral body tethering is less than with a thoracic fusion.”
“We hypothesized that this would result in less spontaneous correction especially in the larger thoracolumbar/lumbar curves (Lenke type C). Our hope is this information will allow surgeons to help decide when thoracic vertebral body tethering is indicated or when additional interventions may be needed for the thoracolumbar/lumbar curve.”
Dr. Yaszay, also chief of Orthopedics and Sports Medicine at Seattle Childrens Hospital, added, “The results are important addition to a growing body of work in vertebral body tethering.”
“Maybe,” commented Dr. Shah to OTW, “we can be more patient and see what happens with tethering or correction of the thoracic curve first, then determine if this is enough surgery for the patient and perhaps avoid any surgery on the lumbar spine at all. This is the ultimate in motion preservation.”
