Anterior vertebral body tethering for idiopathic scoliosis: how well does the tether hold up?

PURPOSE: Durability of outcomes following vertebral body tethering (VBT) is a concern and may be impacted by tether breakage (TB), which has been unstudied in a large cohort. We characterized TB rates and their impact on clinical outcomes in the largest single-surgeon series to date. METHODS: Inclusion criteria were VBT patients with AIS, major Cobb angle ≤ 75°, and minimum 2-year follow-up (FU). TBs were identified on 1- and 2-year FU X-rays. TB rates between single-cord and double-cord tethers were evaluated using two-proportion z test. Curve correction rates and SRS-22 scores between patients with and without TB at 2 years were evaluated using Mann-Whitney U test. RESULTS: 69 patients were included. By 2-year FU, 18 (27%) had experienced TB. TB primarily occurred in major (70%) versus minor curves and thoracolumbar tethers (75%) versus thoracic. TB rates between thoracolumbar single (32%) and double-cord tethers (30%) were not significantly different (p = 0.88). Mean major curve correction at 2-year FU was lower (p = 0.02) in patients with major curve TB (48° to 24°, 50%) versus those without (53°-21°, 60%). 2 patients (3%) required reoperation, 1 due to foraminal encroachment from a screw tip and 1 for curve progression with TB. CONCLUSION: TB rate was 27% at 2 years following VBT. Broken major curve tethers are associated with minor loss of correction that may not be clinically significant. TB rates are higher for thoracolumbar curvatures and double cords may not be protective against TB. Further study of long-term TB rates is imperative. LEVEL OF EVIDENCE: IV.

Early operative morbidity in 184 cases of anterior vertebral body tethering.

Fusion is the current standard of care for AIS. Anterior vertebral body tethering (AVBT) is a motion-sparing alternative gaining interest. As a novel procedure, there is a paucity of literature on safety. Here, we report 90-day complication rates in 184 patients who underwent AVBT by a single surgeon. Patients were retrospectively reviewed. Approaches included 71 thoracic, 45 thoracolumbar, 68 double. Major complications were those requiring readmittance or reoperation, prolonged use of invasive materials such as chest tubes, or resulted in spinal cord or nerve root injury. Minor complications resolved without invasive intervention. Mean operative time and blood loss were 186.5 ± 60.3 min and 167.2 ± 105.0 ml, respectively. No patient required allogenic blood transfusion. 6 patients experienced major (3.3%), and 6 had minor complications (3.3%). Major complications included 3 chylothoracies, 2 hemothoracies, and 1 lumbar radiculopathy secondary to screw placement requiring re-operation. Minor complications included 1 patient with respiratory distress requiring supplementary oxygen, 1 superficial wound infection, 2 cases of prolonged nausea, and 1 Raynaud phenomenon. In 184 patients who underwent AVBT for AIS, major and minor complication rates were both 3.3%.