Tether Breakage Across First-generation and Second-generation Vertebral Body Tethering Devices in Treating Adolescent Idiopathic Scoliosis

BACKGROUND: Tether breakage is a significant complication that can occur when performing vertebral body tethering (VBT) in patients with adolescent idiopathic scoliosis (AIS). While previous studies have reported tether breakage rates, the incidence of tether breakage across medical device manufacturers and VBT models remains unknown. This study aims to define the rate of tether breakage in second-generation device systems compared with their first-generation counterparts.

METHODS: A retrospective analysis of a prospectively collected, multicenter registry was performed for all patients with AIS treated from 2011 to 2021 who underwent thoracic VBT with at least 2 years of follow-up. Radiographic tether breakage, as defined by an increase in adjacent screw angle >5 degrees during the postoperative period, was analyzed across the first-generation and the second-generation vertebral body tethering devices from within the same product line. Wilcoxon rank tests and Fisher's exact tests were performed to compare differences across cohorts.

RESULTS: Two hundred thirty-one patients across 12 centers were included in the final analysis. One hundred seventy-nine patients received first-generation implants from 2011 to 2018, and 52 patients from 2017 to 2021 received second-generation vertebral body tethering devices. In total, radiographically identified tether breakage occurred in 116 patients (50%). The rate of radiographic tether breakage did not differ across generations (52% vs. 44%; P =0.46). Four patients (8%) who received the newer VBT system underwent revision compared with 15 patients (8%) who were implanted with first-generation instrumentation ( P =0.87). In addition, only 1 patient (2%) who received the second-generation device and 8 patients (4%) who received the older VBT system were converted to posterior spinal fusion within 2 years of index surgery ( P =0.69). Interestingly, the surgeon observed rate of tether breakage significantly decreased from the first generation of VBT devices to the second (21% vs. 2%; P <0.001).

CONCLUSION: Tether breakage remains high in cases when using the new tether devices and is comparable to rates observed with the older models, despite lower rates of surgeon-reported breakage.

LEVEL OF EVIDENCE: Level III.