Anatomical Study of C2 Pedicle and Pars Interarticularis in Thai Population
Akkapong Nitising MD*, Keerati Charoontamwong MD*, Chumpol Jetjumnong MD**, Luckchai Phonwijit MD*, Bunpot Sitthinamsuwan MD*
Affiliation : * Division of Neurosurgery, Department of Surgery, Faculty of Medicine Siriraj Hospital, Mahidol University, Bangkok, Thailand ** Neurosurgery Unit, Department of Surgery, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand
Background : The C2 pedicle and pars interarticularis complex have distinct anatomy and substantial variation in the
population. The exact locations of the C2 pedicle and pars interarticularis are still controversial.
Objective : This study aims to determine the safe trajectory and length of C2 pedicle and pars screw insertion.
Material and Method: Thirty-six dried cadaveric C2 vertebrae were used in this study. The authors measured four linear and
four angular parameters of C2 pedicle and pars interarticularis by using a Vernier caliper and a digital goniometer.
Results : Regarding C2 pedicle screw placement, the entry point is a point 5 mm inferior to the superior border of the C2
lamina and 7 mm lateral to the lateral border of the spinal canal, the axial angle is 30°, the sagittal angle is 28° and the length
of the distance is 27 mm. For C2 pars screw insertion, the appropriate entry point is a point 3 to 4 mm superior and lateral
to the medial aspect of the C2-3 facet joint, the axial angle is 16° , the sagittal angle is 36° and the length of the distance is
30 mm.
Conclusion : The authors proposed recommendation for safe C2 pedicle and pars screw placement. These landmarks are
suitable for Thai population.
Keywords : C2 vertebra, Axis, Pedicle, Pars interarticularis, Anatomy, Screw placement
