Feasibility and outcome of stand-alone trans-articular screw fixation in atlantoaxial instability in children less than 8 years of age.

PURPOSE

To study the feasibility and outcome of stand-alone trans-articular screw (TAS) fixation for atlantoaxial instability (AAI) in children less than 8 years of age.

METHODS

This prospective study was conducted between 2009 and 2014. Thirteen children suffering from AAI were operated for a TAS fixation. Feasibility of TAS fixation was assessed on CT scan and a screw diameter was chosen based on C2 isthmus diameter. Demographic data collected included the etiology for AAI, age, and sex. Intra-operative data recorded was the duration of surgery, blood loss, vertebral artery injury or any adverse event. Radiological evaluation included pre- and post-operative atlantodens interval (ADI) and space available for cord (SAC) and fusion was evaluated at 3, 6, 12 and 24 months. Statistical analysis was done using SPSS software and statistical significance was set at p < 0.05.

RESULTS

The mean age of the final study group was 6.1 ± 1.5 years, with nine males and four females. Mean isthmus diameter on the left and right side was 3.3 ± 0.3 and 3.2 ± 0.2 mm, respectively. Five patients had an isthmus diameter of < 3.2 mm and a 2.7 mm Herbert screw was used in them and in nine patients, a CCS of 3.2 mm was used. Mean pre- and post-op ADI and SAC improved from 5.5 ± 0.8 to 3.1 ± 0.1 mm, respectively, and 9.8 ± 2.8 to 14 ± 0.6 mm, respectively. Fusion was seen in all patients.

CONCLUSIONS

Stand-alone TAS with morselized allograft is safe, feasible and successful in managing AAI in children below 8 years of age. These slides can be retrieved under Electronic Supplementary Material.