Smart implants

Broken bones are painful, and healing is generally a long, drawn-out process. Particularly difficult are lower-leg injuries and multiple fractures, frequently the result of a car accident. “Today, after an operation to stabilise a broken bone with screws and a rod, we have to wait a long time before learning how well the injury is healing, and there’s no way to actively support the process. It’s only after several weeks that an x-ray image can show whether healing is progressing well and whether new bone tissue has formed,” explains Professor Tim Pohlemann, director of the department for trauma, hand and reconstructive surgery at Saarland University Hospital.

Knowing how a bone is healing

Professor Pohlemann and his team of researchers from a wide range of disciplines are working at Saarland University to revolutionise therapies for complicated bone fractures. Ultimately, the new processes will help patients recover more quickly while also lowering the cost of medical treatment. “In addition to pain and the extreme immobilization that go hand in hand with a complicated fracture, in the worst case, costs for treatment can quickly reach six figures,” Pohlemann says.

The innovative solution? An implant that can be tailored to the individual patient and that is designed to automatically supply information about the healing process after an operation. The implant’s capacity to autonomously move or stiffen as needed will also positively impact healing.

Optimal exercise regime

“Preliminary studies have revealed that physical stimuli accelerate healing after a bone fracture. Our vision is—so to speak—an implant that follows an optimised exercise regime day and night, allowing a bone to knit better and faster,” Tim Pohlemann says. Another feature will be the implant’s capacity to send a signal if a patient is putting too much weight on the injured bone. To achieve this ambitious goal, Tim Pohlemann and his team at the Saarland University are working closely with engineering professor Stefan Diebels and his research group for technical mechanics, with IT professor Philipp Slusallek and his team at Saarland University and the German Research Center for Artificial Intelligence, and with professor Stefan Seelecke and his team of specialists in intelligent material systems at Saarland University and the Center for Mechatronics and Automation Technology.

Insole sensors

In five years at the latest, the researchers aim to have developed an implant prototype by combining state-of-the-art materials technology, artificial intelligence and medical know-how. Lower-leg fractures, which are frequently highly complex, will be the first type of broken bone treated. For some time now, the researchers have been examining the exact effects that the physical stress of walking has on healing processes by using insole sensors to measure 60 different parameters of every step a patient takes. Over the course of extended studies, the sensors collect data on broken bones that are subjected to different degrees of physical stress (called mechanical loading). The team also analyses countless computer tomography scans. The researchers are mainly interested in what happens when pressure or weight is put on the fracture area. “When we know how pressure will be distributed in a specific case, and once it’s clear what forces are at work, we can geometrically configure the form of an implant for each individual fracture. We’ll also know how many screws are actually needed—and where they should be,” explains Professor Stefan Diebels. Using methods of artificial intelligence and machine learning, the researchers interpret the data collected and develop patterns of mechanical loading, thus allowing them to draw conclusions about positive healing processes or setbacks. “The goal is to make an individual fracture calculable and optimise the therapy for each patient,” is how Professor Philipp Slusallek describes the project’s overarching aim.

Innovative material

Professor Stefan Seelecke and his team are working on manufacturing implants from an “intelligent” material: nickel-titanium, or nitinol, an alloy that is safe to use in the human body. Electric signals move the material’s ultra-fine wires, which are also called artificial muscles. “Of all drive mechanisms, these ‘wire muscles’ have the highest energy density and can create powerful motions in a very small space,” Seelecke explains. The sensor’s properties are automatically integrated into the wires. “The wires deliver all the data, and we can use their sensor properties to stimulate the fracture with targeted, autonomous and smart movements.”

8 million euros from the Werner Siemens Foundation

“At Saarland University, we are absolutely delighted about the funding. This research is a true flagship project and exemplary for excellent interdisciplinary work. The innovative project with its inter-institutional collaboration is of extreme importance for medical science, and we hope that many patients will benefit from the findings in future, says Saarland University President Manfred Schmitt.