Pediatric Cervical Spine Aneurysmal Bone Cyst with Recurrent Atlantoaxial Rotatory Subluxation Requiring C1-C2 Fusion: A 7-Year Follow-Up Case Report.

INTRODUCTION: Aneurysmal bone cysts (ABCs) of the cervical spine in children are rare, locally aggressive lesions that may compromise spinal stability. Atlantoaxial rotatory subluxation (AARS) is an uncommon association and is typically related to trauma or infection. The coexistence of ABC with AARS, particularly with recurrence of instability after tumor resolution, is extremely rare and presents unique diagnostic and therapeutic challenges. CASE REPORT: An 8-year-old boy presented with progressive neck pain and torticollis without a history of trauma or infection. Imaging revealed an expansile lesion of the C4 lamina consistent with ABC. The patient underwent extended curettage with high-speed burring and halo vest immobilization following intraoperative reduction of associated AARS. Histopathology confirmed ABC. Although the lesion showed complete radiological healing, the patient developed recurrence of AARS within 2 weeks of halo removal. Definitive stabilization with posterior C1-C2 fusion using the Gallie technique was performed. At the 7-year follow-up, there was no tumor recurrence, and stable fusion was achieved; however, subaxial cervical ankylosis developed as a long-term sequela. Despite this, the patient maintained good functional outcomes and normal daily activity. CONCLUSION: This case highlights a rare and previously underreported clinical scenario where cervical spine ABC is associated with recurrent AARS despite successful tumor treatment. It emphasizes that tumor resolution does not guarantee restoration of spinal stability and that early surgical stabilization may be required in recurrent cases. In addition, even limited posterior surgical approaches in the pediatric cervical spine may result in long-term ankylosis. Awareness of these factors and long-term follow-up are essential for optimal management.