Lumbar Spine Research

Finite Element Analysis of Lumbar Spine Fusion

Ravikumar Varadarajan, F. Amirouche

During the past few years, the development of cage technology for Lumbar Interbody Fusion has increased because it is less invasive than traditional methods.

Though considerable studies has been done to evaluate Lumbar Fusion, little is known on the effect of fusion on the vertebrae adjacent to fused vertebrae. Heavy contact forces developed due to fusion may degenerate the adjacent healthy Disc. 

Our Finite Element study on the effect of fusion on adjacent vertebrae and Intervertebral Disc in terms of Stress distribution will provide useful data to optimize the cage design and likely to give useful insights to the surgeon.

Some common causes of back problems are disc injury (e.g., herniation) and disc degeneration. Disc degeneration affects about 12 million people in the U.S., of which most are within the ages of 20 to 65. Approximately 10 percent of patients with degenerative discs are candidates for some type of spinal surgery.

 

Finte Element of the cage for analysis in lumbar spine

In your lower back there are five vertebrae (bones). Between each of the vertebra is a disc. Discs are the “shock absorbers” of your spine and act as spacers between vertebrae. As discs degenerate, they lose their water content and height, bringing the vertebrae closer together. This results in a weakening of the shock absorption properties of the disc and a narrowing of the nerve openings between the vertebrae which may pinch your nerves. This disc degeneration can eventually cause back and leg pain or numbness.

The cage system is designed to stabilize and fuse the degenerative disc space(s), with the intent to provide a better alternative treatment for disc disorders.

A 3-D Finite Element Model of the L2-L3 Disc of the Human Lumbar Spine

Q. Lian, F. Amirouche

In this study a 3D Finite Element Model of the L2-L3 vertebra-disc-vertebra unit was developed. The L2-L3 unit was chosen because it is commonly associated with low back pain. The purpose of this study to determine:

• Axial deformation of the model under axial loads.
• Disc bulging under compression and disc necking under tension.
• Stress distribution in the annulus.
• Stress distribution in the cancellous bone.

The predictions of the model under compression were validated by comparison with those of Shirazi-Adl's model. The predications under tension were compared with those under compression.