A study co-funded by STFC and led by a team of researchers from Imperial College London may have uncovered why bone inflexibility can be linked to hip fracture risk.
According to the National Hip Fracture Database Annual Report, hip fractures are a “serious and costly injury” with around 76,000 breaks recorded every year in the UK. The potential of a new preventative treatment for those at risk of hip fractures, or even other bone breakages, could be very significant.
The current preventative treatment uses a bone density scan to assess the likelihood of fractures. Those at risk are then prescribed the medicine bisphosphonate which slows the rate that bone is broken down in your body to help maintain bone density and reduce risk of bone breakage.
However, there is a group of people whose bones appear healthy on the scans but are more likely than others to suffer fractures. To find out why, the researchers took a closer look at the nanostructure of bone, the composition of bone at a smaller scale. This consists of stiff minerals surrounding flexible collagen fibrils, the main structural component in our body, which are responsible for our bones’ resistance to fracture during trips and falls.
Scientific research has shown that our bone tissue will adapt to high-intensity exercise by increasing bone density. For example, the dominant arm of a tennis player tends to have thicker walls than the other arm! Absence of any exercise, or even gravity, can lead to severe bone loss as seen in NASA crew members who have trialled taking bisphosphonate to minimise the loss in microgravity environments experienced in Space.
To examine bone flexibility at nanoscale, the researchers used high energy intense X-ray beams generated by STFC-funded Diamond Light Source, the UK’s national synchrotron, to assess how hip bone samples cope when a physical force is applied. The samples were taken from three groups of donors:
How stiff minerals and flexible collagen fibrils combine at the nanoscale to form bone.
(Credit: Shaocheng Ma, Imperial College London)
Donors without fractures were more likely to have flexible collagen and mineral nanostructures than those who had suffered fractures. Donors with hip fractures and bisphosphonate treatment had lower tissue strength and nanoscale flexibility than the untreated fracture donors and controls. In both fracture groups, the collagen and minerals were less flexible meaning the mineral broke away from the collagen at much lower forces.
“This research really capitalised on the full capabilities of the Small Angle X-ray Scattering Beamline I22 at Diamond. Utilising the full brightness of the beam, 10 billion times brighter than the sun, in a spot 10 times smaller than a human hair, we were able to explore the bone collagen-mineral matrix as it broke in real time, giving new insights into how the structure deforms under these conditions.”
Nick Terrill, Principal Beamline Scientist on I22 at Diamond
When we have a trip or a fall, a bone will bend to absorb energy and avoid a fracture. Researchers concluded that the bones may have fractured because the tissue was too inflexible and could not deform to absorb energy during a bump or fall – highlighting the importance of flexibility in the collagen and minerals of bone.
“We tend to think of our bones as solid, hard support structures, but flexibility appears to be extremely important in bone health.”
Dr Ulrich Hansen, study co-author, Department of Mechanical Engineering at Imperial College London
In the future, researchers could use information about bone flexibility at the nanoscale to predict the likelihood of bone fractures and to investigate potential new drug treatments to prevent bone breakages.
Last updated: 18 December 2020