Finite Element Analysis Comparing the Biomechanical Parameters in Multilevel Posterior Cervical Instrumentation Model...

Area of Science:

• Spine biomechanics
• Orthopedic surgery
• Finite element analysis

Background:

• Limited comparative studies exist on the biomechanics of multilevel posterior cervical fixation.
• Understanding construct behavior is crucial for optimizing surgical outcomes.

Purpose of the Study:

• To compare biomechanical parameters of multilevel posterior cervical fixation using lateral mass screws (LMS) versus transpedicular screws (TPS) at the C7 vertebra.
• To evaluate the influence of C2 pars screw augmentation on construct stability.

Main Methods:

• Four finite element models of posterior cervical fixation were developed.
• Models were subjected to simulated physiological loading to assess failure characteristics.
• Key parameters evaluated included moment, angulation, stress, failure point, and intervertebral disc stress.

Main Results:

• Lateral mass screw (LMS) constructs allowed greater angulation and moment at failure compared to transpedicular screw (TPS) constructs.
• Transpedicular screw (TPS) constructs demonstrated higher maximum stress endurance before failure.
• Intervertebral disc stress was higher with LMS fixation at lower levels (C6-C7, C7-T1).
• C2 pars screw fixation reduced stress at the C2-C3 level in both construct types.

Conclusions:

• Transpedicular screw (TPS) fixation at C7 provides a stiffer and more constrained cervical construct than lateral mass screw (LMS) fixation.
• TPS fixation offers superior stress endurance to compressive forces.
• Augmenting fixation with a C2 pars screw enhances overall construct constraint and durability.