Finite Element Study of a Lumbar Intervertebral Disc Nucleus Replacement Device

Area of Science:

• Biomedical Engineering
• Orthopedic Biomechanics
• Spinal Technology

Background:

• Degenerative disc disease is a common cause of back pain.
• Current treatments like spinal fusion and total disc replacement have limitations.
• Nucleus replacement technologies offer a minimally invasive alternative to restore spinal function.

Purpose of the Study:

• To investigate the biomechanical effects of a novel conforming silicone nucleus replacement device.
• To compare the biomechanics of the novel device with a normal intact nucleus and a solid implant.
• To analyze the influence of device design parameters, such as silicone durometer, on spinal biomechanics.

Main Methods:

• Development of a validated 3D finite element model of the human lumbar L3-L4 motion segment using medical imaging data.
• Simulation of various loading conditions including axial compression, flexion/extension, lateral bending, and axial rotation.
• Analysis of key biomechanical parameters: compressive displacement, endplate stresses, reaction moment, and annulus stresses.

Main Results:

• The novel nucleus replacement device demonstrated biomechanics similar to the normal intact nucleus, with slightly higher reaction moments.
• A solid silicone implant resulted in decreased displacement and increased endplate stress compared to the novel device.
• Increasing the silicone durometer of the novel device led to decreased compressive displacement and annulus stress, but increased endplate stress and reaction moment.

Conclusions:

• The novel conforming silicone nucleus replacement device effectively replicates the biomechanics of a healthy intervertebral disc.
• Finite element analysis confirms the device's potential as a viable, minimally invasive treatment for degenerative disc disease.
• Device design, particularly material durometer, significantly influences spinal biomechanics, offering avenues for optimization.