[Effect of C(1-2) venous sinus upon operative safety of atlantoaxial screw insertion].

Objective: To introduce a new C(1) screw insertion technique to avoid injury to C(1-2) venous sinus in posterior atlantoaxial fixation.

Methods: 48 cases (96 sides of C(1) screws) undergoing posterior atlantoaxial fixation were retrospectively analyzed, including 28 cases of C(1) or C(2) fresh fracture and 20 cases of congenital malformation or old fracture & dislocation, among which 12 cases (24 sides) were operated by Goel lateral mass screws, 14 cases (28 sides) by TAN Mingsheng C(1) transpedicular screws and 44 sides of C(1) screws in 22 cases were inserted via notch on underside of C(1) posterior arch combined with bone wax column protecting C(1-2) venous sinus.

Results: Bleeding was encountered in five sides of C(1) screws among 26 cases (52 sides) whose venous sinuses were not protected by bone wax column, involving 3 cases of Goel lateral screw implant fixation. There was statistical difference in the incidence rate of bleeding between Goel technique and ours (P < 0.05) while there was no statistical difference between C(1) transpedicular technique and ours (P > 0.05) or between Goel sides of Goel lateral mass screws (12.5%) and 2 sides of C(1) transpedicular screws (7.1%). It occurred in none of 22 cases (44 sides) with our presented technique. There was a significant difference between Goel lateral screw implant fixation and C(1) transpedicular technique (P > 0.05). All the screws were implanted successfully. All cases were followed up and there was not any sign of implant failure.

Conclusions: Our presented C(1) screw insertion technique can provide a better bony landmark and vascular protection, stronger bony holding power and more extensive applicability to reduce injury to C(1-2) venous sinus and increase the surgical safety.