Bone study reveals new method to track fracture risk
Health outcomes for those prone to fracture, particularly the elderly, have significantly improved thanks to valuable research out of the Population Health theme—research that has helped to change one of the world’s leading fracture risk assessment tools.
FRAX, is the top fracture risk assessment tool in the world and is endorsed by leading national osteoporosis management guidelines worldwide. It uses algorithms to predict 10-year probabilities for hip and major osteoporotic fractures.
However, data from the Population Health theme’s Geelong Osteoporosis Study (GOS), a long-standing population-based study, had previously demonstrated that DXA-derived bone mineral density, the standard technology for estimating fracture risk, is a poor discriminator of fracture. GOS data were pooled with data from other large studies from across the world, to reveal that the addition of the trabecular bone score (TBS) – a grey scale surrogate measure of bone microarchitecture at the spine—to the calculated FRAX score can improve fracture risk predictions. TBS is computed from the dual energy x-ray absorptiometry (DXA)-derived spine scan by TBS iNsight software.
The GOS data have thereby contributed to an international evidence base to support a role for TBS in the management of patients with osteoporosis or who are at risk of fracture. And now thanks to the evidence, the FRAX calculation tool can be adjusted for TBS.
“The diagnosis of fracture risk is still not perfect,” Population Health theme leader Professor Julie Pasco says.
“New methods are being investigated for improving fracture risk assessment because if people sustain a fracture, especially a hip fracture, it is a major catastrophe to their health and wellbeing. Only a small proportion of elderly people who have a hip fracture get back to their normal level of independence and mobility. This is particularly evident for men.
“Only a small proportion of elderly people who have a hip fracture get back to their normal level of independence and mobility … So anything that can be put in place to prevent [fracture] is valuable.”
“The problem of broken bones is often not considered a risk to health, but for people who suffer a fracture it can be a major upheaval. Hip fracture is arguably the biggest catastrophe that you can have associated with osteoporosis. So anything that can be put in place to prevent it is valuable.
“Bone tissue is being turned over all the time—it is continually undergoing restructuring. It is a reservoir for minerals, produces red and white blood cells and is interconnected with the metabolism that goes on in the body. Bone is a live tissue that plays an important role in people’s health.”
PhD student Kara Anderson worked with her supervisors to develop population-based, age and sex-specific normative data for TBS, which indicated that TBS is less affected by age-related degenerative changes in the spine than bone density measures. This work shows clear translation of the data to improve clinical practice.
“We have demonstrated that TBS has particular advantages over bone density when assessing fracture risk in people living with diseases such as type 2 diabetes and other conditions wherein bone density readings from the DXA can be misleading,” Prof Pasco says.
One of the new devices the GOS team is testing is the OsteoProbe—the team is the only group of researchers trialling the tool in Australia.
“This handheld device tests a different property of bone and uses a different method altogether,” Prof Pasco says.
“You use it on the lower leg, on the middle of the shin bone, and this probe penetrates through the skin and rests on the bone. And then as you push the probe down, it delivers a certain force. You measure how far the probe goes into the bone on a microscopic scale—it is a microscopic indentation into the bone. It’s tailored to measure how well the cortical or compact bone there resists the spread of microfractures.
“We’re in the process of collecting data using this new device. Once again, this new information about bone strength is probably going to be complementary to the information that you get from the DXA. It might help improve fracture prediction. Importantly, it might help younger people who are under 60, as well as older people.
“It might identify people who, despite low bone mineral density, might not be at increased risk of fracture, as well as going the other way, people who might be at high risk but have apparently normal bone mineral density.”
Prof Pasco says they are already making some promising discoveries in their study into the OsteoProbe.
“Dr Kara Holloway-Kew found that people with type 2 diabetes have a higher risk of fracture, but paradoxically, their bone mineral density is higher,” Prof Pasco says.
“There’s something different with their bone structure that increases fracture risk associated with diabetes that’s not detected using DXA. Our preliminary work with men in the Geelong Osteoporosis Study to date has shown that we can see differences in the OsteoProbe readings between those with diabetes and those without, where you can’t see corresponding differences in their DXA-derived measures of bone mineral density.
“We’ve just finished collecting that data. And so as time goes on, we’ll be collecting information on fractures that have occurred after that measurement was taken. And then we’ll be able to see whether it indeed does help with predicting fracture risk.
“Dr Pamela Rufus-Membere worked with the team to develop a world-first set of reference values for OsteoProbe measures in men. Very soon we’ll be getting similar data for women in our study using this new device.”