Posterior screws-rod fixation and selective axial loosening for the treatment of atlantoaxial instability or dislocation caused by os odontoideum: a case series for a single posterior approach.

OBJECTIVE: To evaluate the effect of screw-rod fixation and selective axial loosening in the treatment of atlantoaxial instability or dislocation (including reducible and irreducible) caused by os odontoideum (OO) via a single posterior approach. METHODS: A consecutive series of patients with OO surgically treated in our hospital were retrospectively analyzed. For atlantoaxial instability and reducible atlantoaxial dislocation, C1-C2 screw-rod fixation and fusion were performed. OO combined with irreducible atlantoaxial dislocation was reduced after posterior axial loosening, followed by screw-rod fixation and fusion. The general information, clinical data, and radiographic data were compared between the 2 different procedures. RESULTS: There were 41 patients with an average age of 40.6 +/- 21.7 years. All the patients underwent posterior reduction and C1-2 screw rod fixation, 6 with axial loosening and 35 without axial loosening. The clinical manifestations and radiographic data significantly improved after the operation with a low rate of complications. Except for clivus-canal angle and visual analogue score of cervical pain, there were no differences in clinical and radiographic data between the 2 procedures. CONCLUSIONS: Posterior screws-rod fixation and selective axial loosening is appropriate for treating OO complicated with atlantoaxial instability or dislocation (including reducible and irreducible) without the need for anterior decompression.