A model for studies of the deformable rib cage

Area of Science:

• Biomechanics
• Biomedical Engineering
• Skeletal Mechanics

Background:

• Previous models of rib cage mechanics lacked detailed representation of scoliosis-induced rib deformities.
• Rigid rib segments in earlier models limited the accurate simulation of complex spinal conditions.

Purpose of the Study:

• To develop and validate a modified rib cage model capable of representing scoliosis-related rib deformities.
• To investigate the biomechanical behavior of the rib cage in scoliotic patients using a novel computational model.

Main Methods:

• Replaced rigid ribs with five-segment deformable ribs, assigning stiffnesses based on cadaver data.
• Validated model against experimental data for individual rib and whole rib cage deflections (in vivo and in vitro).
• Quantified scoliotic rib cage deformities using parameters like lateral offset, axial rotation, volume, and distortion in simulated CT planes.

Main Results:

• Bending stiffness significantly impacted individual rib deformation, while shear and tension/compression stiffness had minimal effect.
• Level-to-level differences in rib cage mechanics were primarily attributed to variations in rib shape.
• The model demonstrated good agreement with measured rib cage behaviors in simulations.
• Scoliosis led to minimal overall change in rib cage volume but significant asymmetric distribution and distortion, particularly in simulated CT planes.

Conclusions:

• The enhanced rib cage model accurately represents scoliosis-induced deformities and biomechanical changes.
• Rib shape is a primary determinant of mechanical behavior differences across thoracic levels.
• The model provides a valuable tool for quantifying rib cage distortion and asymmetry in scoliosis.