Biomechanical Evaluation of a Novel Integrated C1 Laminar Hook Combined with C1–C2 Transarticular Screws for Atlantoaxial Fusion: An In Vitro Human Cadaveric Study

Abstract

To evaluate the acute stability of a novel integrated C1 laminar hook (H) combined with a C1-C2 transarticular screw (TAS) with established techniques. A novel integrated C1 laminar hook was tested. Seven human cadaveric cervical spines (C0-C3) were used. The range of motion (ROM) of C1-C2 during flexion-extension, lateral bending, and axial rotation were recorded. The specimens were tested under the following conditions: intact, destabilized (using a type II odontoid fracture model), and destabilized but with internal fixation. The following screw systems were used: bilateral C1-C2 TAS combined with the Gallie (G) technique (TAS+G), C1-C2 TAS combined with a novel integrated C1 laminar hook (TAS+H), C1 lateral mass screw and C2 pedicle screws (C2PS+C1LMS), and novel integrated C1 laminar hook combined with C2 pedicle screws (C2PS+H). The TASs were always inserted after the C2PSs. The C2PS+C1LMS and C2PS+H tests were performed alternatively, as were the TAS+G and TAS+H tests. All fixation constructs greatly improved acute atlantoaxial stability, with no significant difference among TAS+H, TAS+G, and C2PS+C1LMS (all P > 0.05). C2PS+H showed the greatest C1-C2 ROM in axial rotation, significantly different from TAS+G, C2PS+C1LMS, and TAS+H fixation models (all P < 0.05). However, there were no significant differences between C2PS+H and the other 3 models in flexion-extension and lateral bending (all P > 0.05). The TAS+H technique can achieve acute stability comparable to that with the TAS+G technique for treating C1-C2 instability. The C2PS+H is a promising alternative, although it provides less stability in axial rotation than TAS+G, TAS+H, or C2PS+C1LMS.