DRUGS used to treat osteoporosis may be making bones weaker, a 'startling' study carried out in Oxfordshire has revealed.

Patients taking commonly-prescribed bisphosphonate medicines seem to be accumulating more 'microcracks' in their bones than other people the same age.

This was the conclusion of scientists from Imperial College London who used X-Rays at Harwell's Diamond Light Source laboratories.

However, patients have been warned the findings are early-stage and urged to keep taking their medicines.

Writing in the Nature journal Scientific Reports, the researchers reported that bone samples taken from fracture patients who had been receiving long-term bisphosphonate treatments for more than a year demonstrated 'significantly' more microcracks and a reduced mechanical strength.

Lead author Dr Richard Abel said: "Although this is a very small, early-stage study, the results are quite startling.

"This research suggests that, in a small number of patients, rather than protection against fractures bisphosphonates may actually make bones more fragile."

Bisphosphonates are one of the commonest therapies for osteoporosis, and act by reducing bone remodelling – the lifelong process through which mature bone tissue is removed and new bone tissue is formed.

In osteoporosis, the breakdown of older or damaged bone outpaces the rebuilding with new bone, leaving them more prone to damage.

Some 190 million prescriptions for bisphosphonates are issued worldwide every year.

Dr Abel said it was imperative that more funding be found for larger studies to confirm his team's findings.

He went on: "These drugs are not only prescribed to those with osteoporosis, but in combination with some cancer treatments. As our population ages the demand for effective treatments will only increase."

To investigate the effect of bisphosphonates, the researchers analysed samples from fracture patients and compared these to samples taken from healthy cadavers, using one of Diamond’s imaging beamlines, I12.

They visualised the microdamage using X-ray micro-CT scans, which offers the unique capability to gain high-resolution images from deep within the bone sample.

The microcracks they discovered were typically 30-100 µm in length – approximately the same as the width of a human hair.

Dr Abel said: "These microcracks are like the small cracks that emerge when you repeated flex a plastic ruler.

"They gradually weaken the structure and may make it more prone to breaking."

Professor Laurent Chapon, director of physical sciences at Diamond, said it was great to see how micro-computed tomography at Diamond had provided an insight into the possible problem.

He went on: "The X-ray beamline used to map these microcracks is mostly employed by scientists to address engineering or environmental problems, so it is good to see that the development of techniques in physical sciences have a direct benefit to medical research as well."