Anterior Transarticular Crossing Screw Fixation for Atlantoaxial Joint Instability: A Biomechanical Study

Abstract

Objective To evaluate the biomechanical stability of anterior transarticular crossing screw (ATCS) and compare it with anterior transarticular screw (ATS) which may provide basic evidence for clinical application. Methods Eight human fresh cadaveric specimens (occiput-C4) were tested with 5 conditions including the intact status, the injury status (type II odontoid fracture), the injury+ATS fixation status (traditional bilateral ATS fixation); the injury+unilateral ATCS fixation status; and the injury+bilateral ATCS fixation status. Specimens were applied to a pure moment of 1.5 Nm in flexion-extension, lateral bending, and axial rotation, respectively. The range of motions (ROMs) and the neutral zones (NZs) of C1 to C2 segment were calculated and compared between 5 status. Results ATS and ATCS fixations significantly reduced the motions in all directions when compared with the intact and injury statues (p 0.05). Three fixations resulted in similar NZs in all directions (p > 0.05). Conclusion ATCS is a biomechanically effective alternative or supplemental method for atlantoaxial instability.

Keywords

• cervical spine
• atlantoaxial joint
• joint instability
• biomechanics
• cadaver
• internal fixators