Effects of lumbar arthrodesis on adjacent segments: differences between surgical techniques

Area of Science:

• Biomechanical analysis of spinal fusion techniques.
• Finite element modeling of the lumbar spine.

Background:

• Posterior rigid fixation with transpedicular screws is common for lumbar arthrodesis, offering stability and fusion rates.
• Concerns exist regarding increased stress on adjacent segments with rigid fixation, necessitating comparative analysis of different surgical approaches.

Purpose of the Study:

• To evaluate and compare the biomechanical effects of various lumbar arthrodesis techniques on adjacent spinal segments.
• To determine differences in stress distribution among anterior lumbar interbody fusion, posterior lumbar interbody fusion, and semirigid/rigid fixation methods.

Main Methods:

• Development and validation of a finite element model of the human lumbar spine (L2-L5).
• Analysis of four distinct arthrodesis models: anterior lumbar interbody fusion, posterior lumbar interbody fusion, posterior lumbar interbody fusion with semirigid fixation, and posterior lumbar interbody fusion with rigid fixation.

Main Results:

• The rigid fixation model exhibited the highest stress, increasing intervertebral disc pressure and facet joint contact forces in adjacent segments.
• Anterior lumbar interbody fusion demonstrated the lowest stress on adjacent segments.
• Semirigid fixation resulted in intermediate stress levels compared to rigid and anterior methods.

Conclusions:

• Surgical technique significantly influences the biomechanical impact of lumbar arthrodesis on adjacent spinal segments.
• Semirigid fixation presents a promising alternative, potentially reducing adjacent segment stress compared to rigid fixation while preserving stabilization benefits.
• Further research into semirigid fixation for lumbar arthrodesis is recommended.