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Advances in disc replacement mechanism improve surgical treatment for chronic low back pain

/ Author:  / Reviewed by: Joseph V. Madia, MD

(RxWiki News) Disc replacement surgery can provide relief to those suffering from chronic back pain by restoring motion to the spine. Unfortunately, current designs are limited in their capabilities.

Recent studies show the ability of the spine to rotate and torque in multiple directions is vital to the healthy operation of surrounding tissue and adjacent segments. Engineers at Brigham Young University (BYU) have outlined the design, development and functionality of a new disc replacement that takes these concerns into consideration.

"Speak to your doctor about chronic low back pain treatments."

The human spine consists of 23 cartilage-filled discs that hold the vertebrae together and allow for spine movement. When they degenerate or migrate from their position, they can cause chronic pain that inhibits daily activity and can result in loss of work.

The new disc replacement design incorporates compliant mechanisms.

Compliant mechanisms are jointless, elastic structures that use flexibility to create movement, much like tweezers, fingernail clippers or a bow and arrow. The BYU design consists of two plates with a mobile center. The mobile center is constrained by flexures that allow it to roll in multiple axes of rotation.

The compliant mechanism disc replacement mimics the response of the spine more naturally than previous disc replacements. Current designs rely on either the surrounding tissue which may accelerate degeneration or include an additional elastic element, such as springs, which can become overly complex.

The design and testing was led by Larry Howell, a leading expert in compliant mechanism research, and Anton Boden. BYU students built prototypes, machine-tested the disc and tested the devices in cadavers.

One concern with the new design is that it provides motion through deflection, which couples motion with stress. Material and design characteristics become very important in this scenario to prevent fatigue failure. A large range of biologically compatible materials currently exist, including materials that could possibly deliver infinite life.

Infinite life occurs when the applied stress is below the endurance limit of the material so the material does not experience failure.

Licensing of the biomedical device has been granted to a Utah-based company, Crocker Spinal Technologies. The company was founded by BYU President's Leadership Council member Gary Crocker and headed by BYU MBA graduate David Hawkes. Halverson, a lead author on the review of the devices recently published in the International Journal of Spine Surgery, has taken a position at the company.

Reviewed by: 
Review Date: 
June 20, 2012
Last Updated:
November 12, 2012