Spine Growth Modulation in Early Adolescent Idiopathic Scoliosis: Prospective US FDA IDE Pilot Study of Titanium Clip-Screw Implant at Two to Five Years

STUDY DESIGN: Prospective longitudinal study of novel growth modulation system for early adolescent idiopathic scoliosis (AIS), consecutive case series from first human use to study endpoint at skeletal maturity, fusion, or five years postoperation. OBJECTIVES: Determine adverse events and curvature changes to end of study; examine factors most likely to explain variability in curve changes. SUMMARY OF BACKGROUND DATA: Pilot clinical safety study was performed under US Food and Drug Administration (FDA) Investigational Device Exemption (IDE). Safety and radiographic results were previously reported to 24 months postoperation. METHODS: Subjects with early AIS underwent thoracoscopic placement of titanium clip-screw devices designed to modify growth asymmetrically. Eligibility was based on high risk of progression to 50°: single major thoracic curve 25°–40°, Risser 0, open triradiate cartilages, and premenarchal if female. Six subjects, the maximum allowed, enrolled. Adverse events (AEs), clinical outcomes, and curvatures were systematically collected. Disc heights, vertebral heights, and implant-bone contact areas were assessed. RESULTS: Consecutive subjects enrolled, aged 12.1 years (±1.7), three were female. AEs from two to five years postoperation included deformity changes leading to a second surgery in three patients: two for posterior spinal fusion, and one for thoracoscopic removal of half the implants for overcorrection. One patient, whose curve exceeded 50° at 18 years, did not choose fusion. Major thoracic curves were 34° (±3°) preoperatively and 42° (±20°) at end of study. CONCLUSIONS: In a study of spine growth modulation in patients with early AIS with high risk of progression, at skeletal maturity or five years postoperation, major thoracic curves of half progressed to >50°, whereas curves of the other half remained