Atlantoaxial Rotatory Instability in a Down Syndrome Patient with Aberrant Vertebral Artery Anatomy

Abstract

Atlantoaxial instability (AAI) is a common deformity in Down syndrome (DS). Although often inconsequential, AAI can progress to atlantoaxial rotatory subluxation (AARS). In patients with DS, concomitant AAI often necessitate surgical fusion, but successful stabilization in this population can be challenging due to high complication rates. A 14-year-old male with DS presented with a 3-month history of spontaneous AARS. After failed closed reduction, the parents consented to surgical stabilization. Preoperative planning revealed a high-riding vertebral artery and thin C2 lamina; therefore, C1-C4 segmental posterior instrumented fusion was performed, resulting in a successful reduction maintained at 12 months’ follow-up. The development of rigid fixation for the treatment of AARS has improved fusion rates in children with DS. However, vascular and osseous anomalies in this population often dictate extension of the fusion constructs beyond C1 and C2. Careful preoperative planning is a prerequisite to safe and solid fixation.