Healing signals from the bone: towards the world's first continuous healing sensor
In 2018, the Concept Development Focus Area at the AO Research Institute Davos (ARI), with AO Development Incubator (AODI) support, continued its work to develop the AO Fracture Monitor. This is an implantable biofeedback sensor device for the continuous monitoring of fracture healing status and patient activity for controlling fracture healing and early detection of delayed healing or non-union.
The sensor can be attached to plates and external fixators, operates autonomously, enables wireless patient data transfer to a smartphone, and thereby supports patient-specific decision-making.
It works by tracking the deformation within the fracture under functional loading, gathering data on the magnitude and frequency of these events: essentially telling us how much movement the fracture is seeing and when, until the movement fades out when the fracture is healing. It operates autonomously and transfers data wirelessly which means a patient's doctor can monitor the healing process without the patient having to come into hospital: this is particularly useful in remote or difficult-to-reach locations.
Since this makes it easier for doctors to develop patient-specific treatment pathways tailored to each individual's circumstances, it is a valuable part of the AO's commitment to personalization and digital transformation.
Its origins can be found in the problems that drove the AO's founders: a clear and urgent need to improve patient outcomes in the treatment of fractures and musculoskeletal disorders. While the surgical environment has transformed quite a bit in the 60 years since then, the rehabilitation and recovery phase of treatment remains a 'green field' opportunity for making an impact. The standard of care, assessing healing from x-rays, remains subjective and fragmented, and is after all afflicted with radiation.
Work was already done in the 1960s and 1970s to overcome this issue by looking at measuring healing through implant strain. This idea developed within AO Research Institute Davos over the years into an understanding that objective, continuous and x-ray free healing measurement was needed.
By 2010, the AO Research Institute Davos had developed a first prototype sensor, at that time targeting an intensive research phase to improve their understanding of bone healing. After four years of research, supported by the AO Trauma Research Commission the new tool delivered exciting new insights in fracture repair and, at the same time, triggered the understanding: this has the potential to directly improve patient care. With the advance of digital health care, the Internet of Things, and the advent of the concept of individualized treatment in various areas, the AO understood that this tool is a real possibility.
The years 2014 to 2016 saw a significant amount of trial and error with the fracture monitor. Lessons were learned. Most important perhaps, a mindset change took place. Whereas the project had been driven by a largely academic approach during the early years, it now looks to find its place among active implantable medical devices that meet a real clinical need.
The first clinical trial with the Fracture Monitor on external fixation was launched in 2015, supported by AO Technical Commission, to achieve a clinical proof of concept. In 2017 AO Development Incubator became involved—to help the project progress to a point where it would be able to benefit patients.
Following the successful completion of its first clinical trial, a second clinical study, also supported by AO Technical Commission, on external fixation patients was initiated in 2018 and is ongoing under AO Clinical Investigation and Documentation . With the tailwind provided by AO Development Incubator the implanted version of the Fracture Monitor has progressed significantly in 2018 towards its first application in humans, planned for 2020.