Successful treatment of a C2 aneurysmal bone cyst with hydroxyapatite and calcium sulfate synthetic bone void filler injection: a case report.

Background: Aneurysmal bone cysts (ABCs) are benign, blood-filled neoplasms causing bone destruction, often requiring en bloc resection. However, challenges arise, especially at the cranio-cervical junction, where proximity to critical structures limits en bloc removal. Non-surgical options include selective arterial embolization (SAE) as main treatment, while Denosumab and centrifugated bone marrow emerge as experimental alternatives. We report a case of C2 ABC in a young woman successfully treated with a single injection of biphasic ceramic bone substitute (BCBS) containing hydroxyapatite (HA) and calcium sulfate.

Case description: En bloc resection was deemed unnecessary due to the absence of neurological deficits or deformities, as reported throughout literature evidences. Denosumab administration showed interval tumor change, while SAE was hindered by arterial anastomosis, limiting the possibility of obtaining complete embolization, while significantly increasing cerebral ischemic risks. Repeated intralesional iliac crest bone marrow injection proved ineffective. Subsequently, a single BCBS injection was attempted. A 6-month follow-up computed tomography (CT) scan revealed complete cyst ossification, cortical bone remodeling without artifacts, and spinal canal restoration.

Conclusions: HA and calcium sulfate BCBS vertebroplasty emerges as a promising alternative to SAE and denosumab when surgery is not indicated or feasible. Its benefits include effectiveness after a single injection, complete ossification, cortical bone restoration, and artifact-free imaging. These features make it valuable also in cases of pathological fractures.