BU researchers examine how spinal structure affects fracture rate

A Boston University mechanical engineering professor is attempting to improve spinal fractures predictions using an unusual set of tools – the same used for analyzing stress and strain on bridges and buildings.

Spine fractures affect approximately 20% of men over 50 and 40% of women over 80, according to a report from Boston University. Despite the high rate of occurrence, spine fractures are difficult to predict and get less attention than hip fractures, despite being far more common.

Currently, spine fracture risk is assessed through bone density scans which measure how much bone a patient has and how dense it is. The testing results in a “T-score,” which classifies a person’s bone density as compared with the common population.

The issue with the test is that about 50% of the people who fracture their spines have been categorized as normal based on their T-score, according to Boston University professor Elise Morgan. But Morgan thinks her background in engineering will give her the tools she needs to create a more accurate method of screening.

“As a mechanical engineer I’m thinking, well, we’ve got this exquisite structure that is the spine, and even a single vertebra itself is a fairly complicated structure. The 1st thing we need to do is really understand how these fractures occur. Otherwise, it’s hard to predict whether they will occur. And so that’s really a mechanical engineering problem: How is a structure failing?” Morgan said in a BU release.

Morgan is exploring the structure in hopes of developing a more accurate test for spinal fractures with funding from the National Institute of Health.

To explore how spines compress and fracture, Morgan and her team used human vertebrae from individuals who donated their bodies to science and compressed them until they broke, measuring forces and recording the process with a micro-CT scan.

“We do that imaging while we’re doing the mechanical testing, so we get time-lapse series of images of how the vertebrae are failing,” says Morgan.

Morgan’s team, along with collaborating labs at BU, analyzed the data from the stress-tests to explore exactly when and where vertebrae failed to support the load and broke.

Data revealed that almost all vertebrae, no matter where they were located in the spine, failed when depressions and cracks appeared in the center of the top endplate, rather than in the low-density bone inside, according to a report from BU.

Breakage occurred whether the vertebrae were compressed vertically or flexed in an arch the way spines normally bend when a person bends over, according to the report.

In addition, endplates failed first when the bone was more porous, with a weaker microstructure – which makes sense, but had never been experimentally identified.

The findings may aid in diagnosis for doctors viewing X-rays and CT scans, Morgan said. Often, doctors are able to report depressions of the top endplate, which could indicate a higher chance of spine fracture.

Morgan and her team are using the data to build models to simulate spine fractures as they work towards a predictive test. The group is now integrating CT scans from the famous Framingham Heart Study to further refine the test.

“Right now it’s really hard to identify who is being over-treated for osteoporosis, and who’s not being treated at all but should be,” Morgan said in a BU report. “We want to change that.”

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