Biomechanical effects of structural optimization on the ball-and-socket lumbar artificial disc: A finite element...

Area of Science:

• Biomedical Engineering
• Spine Biomechanics
• Orthopedic Surgery

Background:

• Lumbar disc degeneration causes significant low back pain and disability.
• Lumbar total disc replacement (LTDR) is a motion-preserving alternative to spinal fusion.
• Prosthesis geometry critically influences LTDR biomechanical performance.

Purpose of the Study:

• To investigate the impact of curvature radius and radial clearance on ball-and-socket LTDR biomechanics.
• To analyze effects on lumbar spine range of motion (ROM) and adjacent disc behavior.

Main Methods:

• Developed 3D finite element models of the L3-L5 lumbar spine.
• Simulated LTDR prostheses with varying curvature radii (7-10 mm) and radial clearances (0.1-0.3 mm).
• Evaluated ROM and adjacent intervertebral disc biomechanics under physiological loading.

Main Results:

• Increased curvature radius reduced flexion/lateral bending ROM and elevated annulus fibrosus (AF) stress.
• Nucleus pulposus (NP) stress/strain showed varied responses; total deformation decreased.
• Increased radial clearance moderately enhanced ROM with minor effects on stress and deformation.

Conclusions:

• Prosthesis geometry is crucial for modulating spinal kinematics and adjacent segment loading after LTDR.
• Curvature radius is a primary determinant of biomechanical outcomes.
• Radial clearance acts as a secondary parameter for fine-tuning segmental motion.