Donated human spines are helping a Brigham Young University research team make simulations to test treatments for aching lower backs.

Biomechanical engineer Anton Bowden and his team at BYU, which includes two graduate students and three undergraduates, focus on developing models of the lumbar spine. That lower back is a major source of misery, the No. 2 reason that Americans miss work. And there's a high price tag attached, including workers compensation claims and costly treatments.

The BYU team creates models of the discs, the gel-filled sacs between vertebra that cushion bones. Disc degeneration from age or disease is common, the result often painful.

The computer simulations showing the nuances of complex back movement are possible because of 12 donated human spines, each as individual in terms of size and shape as the people who bequeathed them for research. The work is published in June's Clinical Biomechanics.

A major goal is to help devicemakers move away from reliance on the "average spine" so that innovations can help a broader range of people.

For instance, spinal fusions are expected to balloon dramatically in coming years as baby boomers age, but an alternative surgery, artificial disc replacement, only has discs for that "average" spine. By simulating the stiffness and density of the bone from different-shaped spines, based on X-rays and CT scans, then merging that with soft-tissue data gleaned from magnetic resonance imaging, the researchers can create 3-D images of bones, ligaments and discs of other sizes and then measure their surfaces and where they attach. Spines can be mounted in a mechanical tester that moves it in natural ways, while the computers capture and quantify the motion. From that, the team can create equations that explain how spines with various physical characteristics will move when faced with different pressures and directions. "We know that bone responds like a muscle does," Bowden said. "When you work out, it gets stronger. Sit on the couch and watch TV too much, and it will degenerate." But what happens with a medical device that replaces part of that bone with, say, plastic? How will it act when some of the force passes not from bone to bone, but from bone to plastic? The simulations can answer that. Testing provides a prediction for whether a device will succeed or fail, and it might even be used to design devices for a certain patient population, although that's in the future.

The simulations also can provide information that's not yet available: a predictive look at how long the device will last or what the future might bring. Devices like artificial discs are just a few years old. They have no long history of use. But simulation can run an artificial disc through its paces repeatedly, providing a "fast forward" on how bone and tissue might change and behave over a decade or so. "Quality of motion" between endpoints is also important, he said. "When you're developing those types of devices, you need to be careful not just how far the spine is moving, but how it moves. ... If the design is good in flexion (bending forward) and extension (arching backward) but not in between, it would not perform well for most people. Ultimately, the BYU researcher hopes to make the models freely available to other researchers and devicemakers, who can test their devices against many types of spines and spot weaknesses before they are placed inside a patient.

Co-authors on the paper are Heather L. Guerin and Marta L. Villarraga of Exponent, Avinash G. Patwardhan of Loyola University Medical Center and Jorge A. Ochoa of Archus Orthopedics.

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