Posterolateral paramass approach to lesions located at the anterior c1-2 level: a cadaver study

Objective A novel posteriolateral surgical approach is described that will provide safe access to intradural and extradural lesions located in the anterior part of the spinal cord at the C1-2 level and to the odontoid in single session. Methods A total of five cadavers and two dry C1 vertebrae were used in this study. The study involved obtaining CT scans and MRI of all cadaver groups before and after the procedures. Group 1 Control; Group 2:Unilateral C1 posterior arch was removed, the inferomedial part of C1 lateral mass was removed, and access the anterior and lateral aspects of the spinal cord. Group 3: In addition odontoid was removed,Group 4: In addition unilateral C1- C2 screw was placed. Group 5: In addition bilateral C1-C2 screw was placed. Results The median distance from the midpoint of C1 posterior tubercle to vertebral groove which was removed in groups is 21.4±2.88 mm. The average width of C1 lateral mass was 13.4± 2.4 mm. After the lateral mass was drilled, its width decreased to 10,2 mm.This area was sufficient to open a surgical corridor and reach the anterior of spinal cord and odontoid. After the procedure, no instability was found in group 2 without instrumentation on CT and MRI scans. Conclusions It is possible to access the anterior C1–C2 via a posterolateral paramass approach by drilling 20-30% of the lateral mass, providing an open pathway for easy intervention in C1–C2 intradural lesions. It is also possible to perform odontoid resection using this approach.