'Artificial muscles' help fractured leg bones heal better

Traditional orthopaedic implants have served as passive devices, aligning and stabilising bone fragments after fractures. However, this new technology redefines the capabilities of these implants. “We're developing a smart implant that does not require any additional surgical intervention or equipment,” revealed Professor Stefan Seelecke, who leads research groups at both Saarland University and the Center for Mechatronics and Automation Technology (ZeMA).

Innovation powered by shape memory alloys

At the core of these advanced implants are nickel-titanium 'shape memory' wires, which act as both sensors and mechanical actuators. These wires, no thicker than a human hair, respond to electric currents by contracting or relaxing, simulating the natural movement of muscle fibres. The wires' ability to change shape also changes their electrical resistance, providing valuable data about the healing process at the fracture site.

Professor Paul Motzki, who has a cross-institutional role in smart material systems, explained the unique properties of these wires: “If electric current flows through the wire, the material heats up and adopts a different crystal structure, causing the wire to shorten. When the current is switched off, the wire cools and returns to its original length.” This allows for micro-movements that can effectively 'micro-massage' the fracture site, enhancing the healing process.

Real-time monitoring and control via smartphone

One of the most significant advantages of the smart implant is its ability to provide continuous feedback on the healing process, which can be monitored and adjusted via a smartphone. This integration allows for real-time adjustments to the rigidity at the fracture gap, facilitating optimal healing conditions.

The implant's intrinsic sensor capabilities were highlighted by Susanne-Marie Kirsch, a doctoral researcher: “We can assign precise resistance values to even the smallest deformations, which allows us to extract sensory data.”

Future prospects and impact

The smart implant promises to revolutionise fracture treatment, offering significant benefits such as reduced recovery times, decreased need for additional surgeries, and lower healthcare costs. Moreover, the potential for real-time monitoring and adjustment could lead to personalised treatment plans that adapt to individual healing processes.