Finite element analysis of posterior cervical fixation.

Area of Science:

• Spine biomechanics
• Orthopedic surgery
• Finite element analysis

Background:

• Limited understanding of internal structural responses to loading for subaxial cervical spine fixation techniques.
• Uncertainty regarding the optimal fixation method and the efficacy of stabilization devices for three-column injuries (TCI).

Purpose of the Study:

• To compare the biomechanical stability and structural response of three posterior cervical fixation techniques: pedicle screw (PS), lateral mass screw (LS), and transarticular screw (TS).
• To evaluate the suitability of these techniques for stabilizing three-column cervical spine injuries (TCI).

Main Methods:

• Development and validation of a nonlinear finite element model (FEM) of the C3-C7 cervical spine.
• Reconstruction of three FEMs simulating C4-C6 TCI with PS, LS, and TS fixation.
• Application of compressive preload and pure moments (flexion, extension, lateral bending, axial rotation) to assess biomechanical performance.

Main Results:

• Significant differences in range of motion (ROM) were observed among fixation techniques.
• Pedicle screw (PS) and transarticular screw (TS) techniques provided superior immediate stabilization compared to lateral mass screw (LS) technique.
• Transarticular screw (TS) fixation exhibited minimal stress variability in the device, while lateral mass screw (LS) showed maximum variability. Stress concentration patterns varied across techniques.

Conclusions:

• Transarticular screw (TS) technique is recommended as the primary option for treating cervical TCI.
• Pedicle screw (PS) fixation may necessitate prolonged external bracing to mitigate fracture risks.
• Lateral mass screw (LS) fixation might require supplementary anterior cervical surgery for enhanced immediate stabilization.