What Happens After a Vertebral Body Tether Break? Incidence, Location, and Progression with 5-Year Follow-up.

Abstract

Retrospective review. To study risk factors for anterior vertebral body tether (VBT) breakage. VBT is used to treat adolescent idiopathic scoliosis (AIS) in skeletally immature patients. However, tethers break in up to 48% of cases. We reviewed 63 patients who underwent thoracic and/or lumbar VBT with minimum 5-year follow-up. We radiographically characterized suspected tether breaks as a change in inter-screw angle (ISA) >5°. Demographic, radiographic, and clinical risk factors for presumed VBT breaks were evaluated. In confirmed VBT breaks, the average ISA change was 8.1° and segmental coronal curve change was 13.6°, with high correlation (r=0.82). Our presumed VBT break cohort constituted 50 thoracic tethers, 4 lumbar tethers, and 9 combined thoracic/lumbar tethers; the average age was 12.1±1.2 years and mean follow-up of 73.1±11.7 months. Of 59 patients with thoracic VBTs, 12 patients (20.3%) had a total of 18 breaks. Eleven thoracic breaks (61.1%) occurred between 2-5 years postoperatively, and 15 (83.3%) occurred below the curve apex (P<0.05). Timing of thoracic VBT breakage moderately correlated with more distal breaks (r=0.35). Of 13 patients who underwent lumbar VBT, 8 patients (61.5%) had a total of 12 presumed breaks. Six lumbar breaks (50%) occurred between 1-2 years postoperatively, and 7 (58.3%) occurred at or distal to the apex. Age, gender, BMI, Risser score, and curve flexibility were not associated with VBT breaks, but the association between percent curve correction and thoracic VBT breakage trended toward significance (P=0.054). Lumbar VBTs were more likely to break than thoracic VBTs (P=0.016). Seven of the patients with presumed VBT breaks (35%) underwent revision surgery. Lumbar VBTs broke with greater frequency than thoracic VBTs, and VBT breaks typically occurred at levels distal to the curve apex. Only 15% of all patients required revision. 3.