How Does Anterior Vertebral Body Tethering Compare to Posterior Spinal Fusion for Thoracic Idiopathic Scoliosis? A Nonrandomized Clinical Trial.

BACKGROUND Recently, there has been an increased interest in alternative surgical options for treating idiopathic scoliosis. For instance, anterior vertebral body tethering (AVBT) is an emerging surgical solution used in lieu of posterior spinal fusion (PSF). This technology has been gaining in popularity because of its potential benefits of preservation of spinal growth, motion, and functional activity. Although prior retrospective studies have indicated the potential efficacy of AVBT in patients with primary thoracic curves, a direct comparison to PSF, the most widely used definitive treatment for pediatric scoliosis, has yet to be conducted. Differences in efficacy, quality of life, and revision risk may exist across the techniques. QUESTIONS/PURPOSES We compared AVBT to PSF in terms of (1) the proportion of patients whose main thoracic curve was corrected to < 50° without a return to the operating room for revision within 2 years, (2) residual thoracic and lumbar curve magnitude at 2 years, (3) health-related quality of life (HRQoL) scores, and (4) the frequency of serious complications and healthcare resource utilization. METHODS From 2017 to 2022, patients (n = 87) were assessed for eligibility to participate in an FDA-approved investigational device exemption clinical trial for AVBT based on presenting to the clinic with a diagnosis of adolescent idiopathic scoliosis that had entered into surgical range. Based on clinical characteristics and the family's stated goals of care, AVBT and PSF were both discussed, but ultimately the patient and their family selected their preferred treatment. Under guidance from the FDA, a sample of 20 patients who met the inclusion criteria of a Lenke Type 1 or 2 curve classification, a thoracic curve between 35° and 60°, a lumbar curve < 35°, and a skeletal maturity score of either Risser 0 or Sanders bone age of ≤ 4 were eligible to participate in the trial and undergo AVBT. Patients with Lenke 1 and 2 curves who elected to undergo PSF (n = 27) were prospectively analyzed for comparison. No patients who underwent AVBT and 22% (n = 6) of those who underwent PSF were lost prior to the minimum study follow-up of 2 years, leaving 100% (20) and 78% (n = 21) in each group, respectively, for analysis. All patients in the PSF group who were lost to follow-up did not report any complications at 1 year. Patients who underwent AVBT (80% [16] girls) were generally younger, more skeletally immature, and had smaller preoperative curvature at the time of surgery compared with patients who underwent PSF (81% [17] girls). No differences in gender, height, or revised Scoliosis Research Society-22 (SRS-22) patient questionnaire scores were observed across the two groups at baseline. Patients in both cohorts were followed at the preoperative, first erect, and 2-year time points. Radiographic, health-related quality of life, unplanned return to the operating room, complications, and healthcare resource utilization outcomes were compared. RESULTS Scoliosis curves were reduced to < 50°, without unplanned return to the operating room, at 2 years in 70% (14 of 20) of patients who underwent AVBT and 100% (21 of 21) of patients who had PSF (p < 0.001). No patients who had PSF underwent revisions. Although both groups showed postoperative curve correction, patients who had AVBT showed less curve correction at first erect (35% versus 65% correction; p < 0.001) and at 2 years (34% versus 61% correction; p < 0.001). No differences were found in any revised SRS-22 domains or total score at 2 years between the AVBT and PSF groups (4.3 ± 0.5 versus 4.5 ± 0.4; p = 0.14). No instrumentation complications occurred in the PSF group. Thirty-five percent (7) of patients who received AVBT experienced a tether rupture, and 30% (6) of patients who received a tether required a revision procedure prior to the 2-year follow-up. Intraoperative data revealed that AVBT resulted in a shorter length of stay (2 ± 1 versus 3 ± 1 days; p = 0.02) and fewer levels instrumented (7 ± 1 versus 10 ± 1 levels; p < 0.001); however, there was increased operative time when compared with PSF (231 ± 41 versus 194 ± 26 minutes; p = 0.001). CONCLUSION Pediatric orthopaedic spine surgeons should carefully consider discussing the use of vertebral body tethering with their patients who have adolescent idiopathic scoliosis, as this evidence points to the more established technique of PSF leading to better outcomes. Additional research supporting AVBT as noninferior to PSF in radiographic and safety measures is needed before the procedure becomes widely available to patients and their families. LEVEL OF EVIDENCE Level III, therapeutic study.