Sensing signals from the bone

A sensory implant that transmits bone repair and healing information to the physician has been invented by researchers at the AO Research Institute Davos (ARI).

04 December 2013

The project team (from L to R): Markus Windolf, Erich Zweifel, Manuela Ernst, Ronald Schwyn.

Imagine this: you break a bone, the fracture is healing—and then, a sensory device tells your physician that you're fine and all set to go. The same sensing implant also helps to control and understand the bone healing process better. It detects and warns of healing disturbances at an early point in time. This is monitored by X-rays that can only provide limited information and requires hospital visits. This futuristic technique is not as far from reality as you may imagine. In fact, the AO Research Institute Davos has already developed a sensory implant device called the AO Fracture Monitor.

As part of the Biomedical Services Program at the ARI, the Concept Development Focus Area aims at developing innovative solutions to support surgeons in their daily work to improve patient care. The AO Fracture Monitor has been developed by a team including Manuela Ernst (General Project Coordinator), Ronald Schwyn (Medical device design) and Markus Windolf (Leader of the Concept Development Focus Area). The AO Prototype Toolshop, which is responsible for the manufacture of all non-electronic parts, such as bone plates, etc is being led by Erich Zweifel.

Windolf says, After the basic idea was conceived within the AO Research Institute Davos, the first project work started in 2009 in the form of a Bachelor thesis by two students from Hochschule für Technik Rapperswil (HSR) in close collaboration with Professor Heinz Mathis. After the successful completion of a first prototype, this project became a priority in my team at the AO Research Institute Davos. Regarding the device", he explains, the AO Fracture Monitor consists of an implantable data logger and a wireless receiver connected to a computer. The data logger comprises a sensor and an electronic unit. An implant—like the bone-plate—takes over the stabilizing function of the bone for the time it is broken. The data logger continuously measures the amount of loading (stage of healing based on whether the bone can bear load without an implant). It transmits the information to the physician. The physician can interpret the data for corrective actions such as improved aftercare or required reoperation. Furthermore, the data received can help improve implant designs that ensure proper bone healing.

Technology with a difference

The idea of a sensing implant is not a novelty. Several teams around the world are working on different solutions and are at different stages of completion. But no commercial solution is available yet.

Windolf says, The AO Fracture monitor is different from other approaches in the way that it can measure continuously over long time periods (up to four months). This is comparable, for example, to a time-lapsed video of a growing flower. Approaches by others at the moment are based on snapshot measurements at distinct time points. Besides fracture monitoring, the AO solution also enables the detailed recording of a patient's activity—an important factor for bone healing.

An implant in water-bath testing, with the AO Fracture Monitor device, the size of a 1 franc coin, housed in a small case.

A prize winning invention with potential

The AO Fracture Monitor is currently being tested in preclinical studies in animals. The first clinical handling trials have also been planned for patients with external fixator treatment. External fixators include components like connecting rods, clamps and pins, used to bridge a fracture outside the human body. This offers an interesting opportunity for the described technology, since measurements can be performed without implantation of the device. Patient risks are thereby minimized.

Professor Geoff Richards, Director at AO Research Institute Davos, mentions, It may require some years until this technology will be routinely available for patient treatment—but the potential for improvement with warning of poor healing or non-unions, and the savings on time and cost for the patient, surgeon and insurance companies will be very high.​​​​

Author: Aradhna Sethi
Extracted from: Davoser Zeitung 03.12.2013
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