P88. Ahead of the curve: A systematic review of anterior vertebral body tethering in adolescent idiopathic scoliosis

BACKGROUND CONTEXT Current options for treatment of adolescent idiopathic scoliosis (AIS) include observation, bracing, growth-sparing rods and spinal fusion. The primary treatment for curves greater than 45 degrees at this time is posterior spinal fusion (PSF). Although effective in stabilizing these curves, it is associated with multiple identified morbidities. Thus, anterior vertebral body tethering (AVBT) has recently received growing interest as an effective fusion-less therapeutic option. AVBT harnesses a patient's growth potential to correct pathologic curvatures while preserving the underlying anatomy and structure of the spine, leading to multiple potential benefits. PURPOSE The purpose of this study was to perform a systematic review of the current literature regarding AVBT to determine the current rates of success and complications associated with the procedure. PATIENT SAMPLE Eight studies were identified with a total of 188 patients, 85% of which were female, with a mean follow-up of 34 months. The mean patient age was 12.3 years, with a mean preoperative Sanders age of 4.4 and Risser sign of 0.7. The mean number of vertebral levels tethered was 7.2. The mean main Cobb angle preoperatively, at first erect, and at last follow-up was 48.4°, 23.8°, and 19.1°, respectively. OUTCOME MEASURES The main outcome measure was clinical success, defined by patients who reached skeletal maturity with a remaining curve less than 35 ° without the need for revision operation or conversion to PSF. Additionally, complications were identified and recorded which include: broken tethers, tether revision surgery, curve overcorrection, progression of curve, pulmonary complication and need for revision surgery or PSF. METHODS A systematic review was performed using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) protocol. PubMed, Cochrane Reviews, Web of Science, and Medline databases were searched for studies that investigated AVBT. Search terms included “vertebral body tethering,” “adolescent idiopathic scoliosis,” “fusionless spine surgery”, “growth modulation”, “Hueter-Volkmann law,” and “thoracoscopic.” Studies were selected if they met the following criteria: (1) evaluate outcomes of AVBT for AIS, (2) minimum 2-year follow-up, (3) publication in peer-reviewed journal, (4) English language or translation readily available. RESULTS There were 74.2% (138/186) of patients who underwent AVBT achieved clinical success. Broken tethers occurred in 30% (57/190) of cases, requiring surgical tether revision in 11.1% (21/190). Posterior spinal fusion was required in 6.9% (13/188) of patients, with the overall rate of required revision surgery being 17% (32/188). The rates of curve overcorrection and progression were equal in this cohort at 7.4% (14/188). Pulmonary complications were noted in 8.0% of cases (15/188). CONCLUSIONS AVBT has the ability to modulate spinal growth with the potential for scoliosis correction while preventing the need of PSF in young patients with AIS. This study demonstrated successful results in 74.2% of patients, suggesting that AVBT may have a role in the future treatment algorithm of AIS. Identification of ideal candidates for AVBT will be critical to the success of the procedure moving forward in order to mitigate the complication rates and need for revision surgery. Future studies will need to investigate the optimal curve types and magnitudes as well as skeletal maturity at the time of surgery to optimize outcomes. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.