Novel atlanto-odontoid joint arthroplasty for atlanto-axial instability: a case report with 7-year follow-up.

BACKGROUND: Instability of the craniocervical junction may compress the spinal cord or nerve roots, causing severe neurological complications. Conventional fusion restores stability but restricts cervical mobility and accelerates adjacent-segment degeneration. Motion-preserving alternatives at this region remain scarce. CASE REPORT: A 42-year-old man with atlantoaxial instability secondary to os odontoideum presented with neck pain, numbness and weakness in all four limbs. Following extensive biomechanical testing on cadaveric and goat models, he underwent transoral odontoidectomy and replacement with a multidimensional artificial atlanto-odontoid joint. His symptoms resolved rapidly, with normal muscle strength restored within two days. At the 7-year follow-up, the implant remained well positioned without major complications, and nearly normal cervical rotation and flexion-extension were maintained. CONCLUSION: This case demonstrates the potential feasibility of artificial atlanto-odontoid joint arthroplasty as a motion-preserving alternative to fusion. Further studies with larger cohorts and longer follow-up are needed to validate its safety and efficacy.