Finite Element Analysis of Horizontal Screw-Screw Crosslink Used in C1-C2 Pedicle Screw-Rod Fixation

Abstract

Background In the craniocervical junction, a C1–C2 pedicle screw-rod (PSR) fixation is applied to provide stability. The horizontal rod-rod crosslink (hR-R CL) is often used to enhance segmental posterior instrumentation. However, the biomechanics of the alternative horizontal screw-screw crosslink (hS-S CL) in the craniocervical junction are unclear. Material/Methods A nonlinear atlantoaxial instability 3-dimensional C1–C2 finite element model was constructed using computed tomography images. On this basis, 2 fixation models were established with C1–C2 PSR fixation using (1) a rod-rod crosslink (R-R CL), and (2) a screw-screw crosslink (S-S CL). Range of motion (ROM) of the atlantoaxial joint, stress distribution of the implants, and maximum stress value of the vertebral bodies were calculated and compared under 4 loading conditions, including flexion, extension, lateral bending, and axial rotation. Results Atlantoaxial joint ROM was reduced by 90.19% to 98.5% with the hR-R CL, and by 90.1% to 98.7% with the hS-S CL, compared with the instability model. During axial rotation, the total stress peak of the PSR fixation was smaller with hS-S CL than with hR-R CL. The peak stress values of the vertebral bodies were comparable between the 2 fixation models. Conclusions The 2 tested crosslink models provided comparable stability. However, during axial rotation, the total stress peak of hS-S CL fixation was smaller than that of hR-R CL fixation. Since the atlantoaxial joint primarily functions as a rotational joint, our results suggested that the use of hS-S CL can provide a more stable environment for the implants.

Individualized 3D printed navigation template-assisted atlantoaxial pedicle screws vs. free-hand screws for the treatment of upper cervical fractures

“…However, a more advanced level of pedicle fixation technology is necessary because of the unique anatomical anatomy of the pedicle of the atlantoaxial vertebra itself. Because of its great stability, high rate of fusion, and effective position correction, posterior atlantoaxial pedicle screw fixation is widely acknowledged by spine surgeons ( 18 , 19 ).…”

Biomechanical evaluation of a novel atlas polyaxial transverse connecting screw system, an in vitro human cadaveric study

“…Our study shows C1 to C2 screw-rod system, C1 to C2 + CL system and APTCS system all can provide comparable stability for atlantoaxial joint, which has the same result as previous studies. [9,10] APTCS has the most stable condition when compare to other groups. For axial rotation direction, APTCS has the least ROM, providing more stable condition for the implants.…”

Biomechanical properties of different anterior and posterior techniques for atlantoaxial fixation: a finite element analysis

“…However, the influence of different atlantoaxial fixation techniques on nonfixed segments remains unclear. Notably, previous finite element studies simulating atlantoaxial fixation only considered the reconstruction of the upper cervical spine rather than the whole cervical spine [ 20 – 22 ]. It is necessary to establish finite element models of the whole cervical spine to better understand how the ROM, disc stress, and FJF change with respect to different fixation techniques and loading conditions for cervical segments.…”