Preliminary outcomes after vertebral body tethering (VBT) for lumbar curves and subanalysis of a 1- versus 2-tether construct.

Abstract

Aim of this study was to analyze the rate of tether breakages after lumbar vertebral body tethering (VBT) and tostudy the effects and possible benefits of the use of a 2-tether construct. Tether breakage is a known mechanical complication after VBT. However, the literature only refers to thoracic VBT, and no data on the breakage rate or 2-tether construct after lumbar VBT are available. Patients who underwent lumbar VBT with lowest instrumented vertebra at L3 or L4 and had a 1-year follow-up were included. Radiologic data were obtained preoperatively, at the 1st standing X-ray and at the 1-year follow-up to study breakage rate, loss of correction and lumbar lordosis in 1- and 2-tether constructs. Data from 30 patients (mean age 14.7 ± 1.8) were available, 12 with double tether. Double tether did not decrease lumbar lordosis. The breakage rate was 24% in segments instrumented with a single tether and 16% in segments instrumented with a double tether (OR 1.6, p = 0.4). Lumbar loss of correction was 10° ± 6.8° in the entire cohort and 12.1° ± 5.4° in patients with a breakage (p = 0.2). Revision rate was 10%, due to tether breakage and loss of correction. Breakage rate after lumbar VBT is high, but was improved with the use of a 2-tether construct. Despite tether breakage, loss of correction was limited and the revision rate low. The use of a double tether does not have a kyphotic effect on the lumbar spine.