[Initial stability of two PLIF-techniques. A biomechanical comparison using a finite element model].

Area of Science:

• Spine Biomechanics
• Orthopedic Surgery
• Finite Element Analysis

Background:

• Posterior interbody lumbar fusion (PLIF) is a common surgical procedure for spinal instability.
• Evaluating the biomechanical impact of different PLIF techniques is crucial for optimizing surgical outcomes.
• Cage selection and supplemental fixation can influence spinal segment stiffness.

Purpose of the Study:

• To compare the initial stiffness of two distinct PLIF techniques using a finite element (FE) approach.
• To assess the biomechanical effects of BAK-Cages versus Harms-Cages with posterior osteosynthesis on lumbar spinal segments.

Main Methods:

• A validated finite element model of a human L3/L4 spinal segment was created.
• The intact model's stiffness was evaluated under compression, torsion, and shear loading.
• Stiffness was simulated and compared after implementing PLIF with BAK-Cages and PLIF with Harms-Cages plus posterior screw-rod-osteosynthesis.

Main Results:

• PLIF utilizing two BAK-Cages led to a reduction in spinal stiffness across compression, torsion, and shear forces.
• PLIF employing two Harms-Cages combined with posterior screw-rod-osteosynthesis resulted in a notable increase in spinal stiffness for all tested loading conditions.

Conclusions:

• The choice of interbody cage and fixation method significantly impacts the biomechanical stability of lumbar fusion.
• Harms-Cages with posterior osteosynthesis offer superior initial stiffness compared to BAK-Cages for PLIF.
• Finite element analysis provides a valuable tool for predicting the biomechanical performance of spinal fusion techniques.