Researchers at the University of Arizona have developed sensors to monitor bone health in real-time. Called osseosurface electronics, the thin devices are attached to bone and provide continuous data, a substantial improvement from periodic imaging of bones.
For patients who have experienced trauma or surgery or are at risk for fracture, an accurate picture of bone health is usually obtained through x-rays or other imaging modalities. But these images only provide a static snapshot of bone health and carry some risk and inconvenience. UA’s device could offer ongoing information on the health of a patient’s bones, potentially staving off delays in rehabilitation or disease exacerbation. The device could also be used in clinical trials to evaluate the efficacy of therapeutics.
Slim Profile for Bone
A thin, wireless device, the biointerface is about 200 microns thick, similar to a sheet of paper, with affixed electronics, said Philipp Gutruf, assistant professor of biomedical engineering and Craig M. Berge faculty fellow with UA’s college of engineering. That slim profile allows the device to be placed against a bone without affecting adjacent muscle tissue and without the risk of the device migrating.
“These devices don’t require a battery—we power them wirelessly so they can be made really, really thin,” said Gutruf. “[This] means you can directly laminate them to the bone and extract important markers of bone health such as bone strength [and] the very localized temperature with milli-kelvin accuracy that allows us to look at inflammation, and you can provide phototherapy.”
Patients who underwent orthopedic surgery or who experienced trauma or fractures could be monitored regularly to evaluate the impact of rehabilitation or therapeutics. The device also could aid in management of patients at risk for fractures due to osteoporosis.
Measuring Pliability in Bone
Strength gauges in the device monitor the movement of bone as an indicator of health. “As you put load on a bone it deforms,” said Gutruf. “With the sensors we can look at how far the bone deforms. Bone deformation looks different when the bone is injured versus when its healthy, and if you have chronic illness like osteoporosis, you can see the progression of the disease as you look at how the bone deforms while you are moving.”
Exploratory Research and Therapeutics
Gutruf explained the device has numerous future applications, including monitoring bone health in human patients, to better understand bone healing, in exploratory studies, and in animal models to evaluate the effectiveness of a pharmaceutical treatment, or implant technology. “There are currently no tools that allow us to get live data on bone health” said Gutruf. “Patients would benefit dramatically if you have a device that provides real-time information on how your bone preforms even under load.”
The device, or musculoskeletal biointerface, was affixed to the outer surface of bone in a large animal model study recently published in Nature Communications. Thanks to the device’s makeup of calcium phosphate ceramics, the sensor grows into the bone rather than being sloughed off as part of the natural remodeling process of bones. “We want a long stable interface with the bone in order to extract bone health information over long periods of time,” said Gutruf. “This is a challenge because anything that you glue to the bone will fall off after a period of time because you have cell turnover.” Generally, devices attached to bone are expelled within a few weeks.
Data from the device can be accessed with a smartphone or specific reader, which also provides power.