Mechanical loading effects on isthmic spondylolytic lumbar segment: finite element modelling using a personalised...

Area of Science:

• Biomechanics
• Orthopedic Surgery
• Computational Modeling

Background:

• Isthmic spondylolysis, a defect in the vertebral arch, is a common cause of low back pain in adolescents.
• Understanding the biomechanical factors contributing to spondylolysis is crucial for developing effective treatments.
• Previous studies have often relied on simplified models, limiting the understanding of complex stress distributions.

Purpose of the Study:

• To investigate the biomechanics of isthmic spondylolysis using a nonlinear 3D finite element model (FEM).
• To analyze stress distribution in the L5-S1 motion segment of a pediatric patient with spondylolisthesis.
• To correlate computational predictions with clinical observations of spondylolysis.

Main Methods:

• Developed a personalized 3D-FEM of the L5-pelvis motion segment using in vivo pediatric geometry.
• Incorporated detailed anatomical structures including vertebrae, intervertebral disc, and spinal ligaments.
• Simulated biomechanical responses under axial loading, and combined flexion-extension forces.

Main Results:

• Predicted significantly higher stress concentrations in the pedicle and dorsal pars interarticularis.
• Demonstrated that abnormal geometry, characteristic of spondylolisthesis, is a key factor in elevated stress.
• Stress patterns were consistent across different loading conditions (axial, flexion, extension).

Conclusions:

• The 3D-FEM effectively simulates biomechanical alterations in isthmic spondylolysis.
• Abnormal vertebral geometry plays a critical role in the pathogenesis of spondylolysis by increasing localized stress.
• These findings support clinical observations and can inform future research on spondylolysis prevention and treatment.