BDAT – a robust tool to examine bone fragility

• As the global population ages, there is an increased risk of fragility fractures, in particular hip fractures.
• Dual x-ray absorptiometry (DXA) is the current gold standard for detecting patients at risk of fragility, although many patients are left misdiagnosed.
• Is there another method to detect the risk of fragility with accuracy?
• Dr Jean-Gabriel Minonzio from the University of Valparaíso, Chile, and collaborators designed and tested a bi-directional axial transmission (BDAT) device, which uses ultrasonic guided waves to estimate the risk of fragility.
• This robust technique can be easily applied in every hospital.

Bone fragility remains a worldwide problem and is a huge burden in patients’ lives, hospitals, and healthcare in general. Among the common bone fractures are hip fractures – a major consequence of osteoporosis, a health condition that weakens the bones, making them fragile and more likely to break. As the world’s population gets older, osteoporosis rates are expected to double between 2018 and 2050.

Consequently, researchers estimate that hip fractures will reach more than 10 million cases per year globally. Fortunately, many hip fractures are potentially preventable, although it is very crucial to identify osteoporosis as their cause.

Until today, dual x-ray absorptiometry (DXA) is most commonly used as the ‘gold standard’ to detect patients at risk of fragility fractures. However, it is not perfect: most patients suffering from fractures are not classified as osteoporotic, mainly because DXA doesn’t capture the material and structural properties of the bones, which are crucial to distinguish osteoporotic bones from the non-osteoporotic. In particular, DXA cannot detect changes located at the cortical bone (the external hard layer of all bones, which is the main contributor to mechanical strength of the bones). That is why there is a huge need for another method to predict bone fracture risk by assessing different bone characteristics.

Dr Jean-Gabriel Minonzio from the University of Valparaíso, Chile, and colleagues designed a novel device, called BDAT (bi-directional axial transmission), which uses ultrasonic guided waves to estimate the risk of bone fragility. The team successfully tested this non-invasive method in a clinical setting.

Current limitations in hip fracture detection

DXA is a procedure that uses x-rays to measure the amount of calcium and other minerals found in the bone. It provides a parameter called bone mineral density (BMD) extracted from the calibrated grey level of the radiographic image. The amount of these minerals reflects on the quality of the bone – ie, how strong and thick it is – and the BMD value is used to diagnose if the patient suffers from osteoporosis or not. However, most patients with bone fractures are left misdiagnosed and are not classified as osteoporotic.

BDAT’s failure rate was less than 10%.

Additionally, the accessibility to DXA is limited in many countries and often restricted to large cities. Minonzio and his team believe that among the DXA alternatives, quantitative ultrasound devices can be by far superior to DXA, mainly due to their portability and lower price.

Moreover, ultrasound being mechanical waves, they are naturally sensitive to both geometrical and mechanical properties of the inspected material. Quantitative ultrasound therefore has the potential to be used as a ‘thermometer’ of the bone quality.

Employing ultrasound devices

Minonzio and colleagues used BDAT to estimate the thickness and porosity of cortical bones at the forearm (radius) and leg (tibia) in about five minutes per body part. This custom‐made guided wave technology includes two specialised probes for forearm and leg measurements, an electronic device for signal transmission and reception, and a human-machine interface for real-time guided display and operator guidance.

Minonzio successfully used BDAT in a clinical setting in a pilot study considering two groups of postmenopausal women, with or without history of fragility fractures. 201 postmenopausal women were included in the study taking place in Cochin Hospital, Paris, France, between April 2014 and November 2015, where Minonzio and coworkers gathered information regarding two important parameters: cortical thickness (Ct.Th) and porosity (Ct.Po). Among their findings, Ct.Po was the most important parameter which could help the researchers discriminate patients with any types of fragility fractures from the control group (patients without fragility fractures) with a classification ability similar to the gold standard DXA. In addition, cortical thickness was found to be a good predictor for the subgroup of patients with hip fragility fractures.

Fracture risk assessment could be performed in a robust, quick, and reproducible way.

In a second cross-sectional study published in 2022, the group examined whether the device could be used in a clinical environment, studying 106 patients in Marien Hospital and St. Anna Hospital in Herne, Germany. In the first study, the device was used by laboratory staff, whereas in the second study, the device was used by nurses, after a two-day training session. The device’s failure rate was less than 10% – this was significantly lower than their previous study (20%), mainly due to the improvements of the guiding interface associated with real-time monitoring of the measurement quality. This study confirmed that the device could be easily used in a clinical environment and that the ultrasonic parameters were particularly helpful to detect non-vertebral fragility fractures, which include hip fractures. In this case, the BDAT classification ability was slightly better than the gold standard DXA.

In a study taking place in the UK, published in the same year, Minonzio and colleagues tried using the device in patients undergoing hip arthroplasty – in other words, hip replacement – where the damaged bone and cartilage are removed and replaced with prosthetic components. This study suggests that the BDAT device could help the surgeon to choose the best prothesis adapted to each patient depending on their bone quality.

Furthermore, in a recent study – soon to be published and presented at conferences – the group examined patients from Chile aged over 50 years old with and without hip fragility fractures. The device’s robustness and user friendliness have been improved once again, confirming that the fracture risk assessment clearly suggests the benefit of the affordable and transportable device for routine use, with performance similar or better than the gold standard.

Minonzio and his group now want to take a step further and use the BDAT device on a larger scale in a clinical environment, in particular in countries where DXA is not widely used. In that way, the fracture risk assessment could be performed in a robust, quick, and reproducible way giving a full image of the clinical status of the bones, especially in people suffering from osteoporosis and fragility fractures.