Learning Curve of Minimally Invasive C1-C2 Trans-articular Screw Fixation (MIS-TAS): Over A Period of Five Years

Abstract

Objective To evaluate the learning curve associated with minimally invasive surgery (MIS) in posterior C1-C2 trans-articular (TAS) screw fixation based on surgical and clinical parameters. Also, to report the challenges faced and measures to overcome them. Methods 84 patients who underwent C1-C2 MIS-TAS between 2009-2014 were included in the study and were divided into four quartiles (q) (21 patients each) based on the date of their surgery with each consecutive group serving as a control for prior. Pre- and post-operative clinical and perioperative parameters, technical issues and complications were evaluated. Results The mean age of the patients was 36.26±5.78 years (20-78 years) with male to female ratio of 48:36. A statistically significant difference was observed between the mean operative time and mean blood loss between second and third quartile. Inadvertent vertebral artery injury occurred in 3 cases without any post-operative sequelae. There were 6 instances of guide wire migration(q1=4, q2=2). At 2 instances (q1=2) there was guide wire breakage. Total 9 times (q1=5, q2=2, q3=1, q4=1) dorsal burst into C2 pars occurred. VAS, ODI and mJOA scores showed a significant improvement from their pre-operative values in the entire study population without any significant difference between the quartiles. Conclusion C1-C2 MIS-TAS is a very safe and effective means of treating reducible atlanto-axial instability. Pre-operative planning, detailed radiological evaluation, practice on cadavers/bone-saw models and by following the mentioned recommendations the learning curve of C1-C2 MIS-TAS can be reduced.

Keywords

• atlanto-axial joint
• minimally invasive
• trans-articular screw
• learning curve
• allograft