The Amputee Coalition estimates that 2 million people in the U.S are living with lost limbs. The Congressional Research Service reports there were more than 1,600 amputations involving U.S. troops between 2001 and 2010.
The Department of Energy’s Sandia National Laboratory researchers using off-the-shelf equipment are working to improve amputees control over prosthetics by using direct help from their own nervous systems. The goal is to improve prosthetics with flexible nerve-to-nerve or nerve-to-muscle interfaces through which transected nerves can grow, putting small groups of nerve fibers in close contact to electrode sites connected to separate implanted electronics.
Neural interfaces operate where the nervous system and an artificial device intersect. Interfaces can monitor nerve signals or provide inputs that let amputees control prosthetic devices by direct neural signals in the same way that they would control parts of their own bodies.
However, the challenges are numerous since interfaces must be structured so nerve fibers can grow through. They must be mechanically compatible so they don’t harm the nervous system or surrounding tissues, and biocompatible to integrate with tissue and promote nerve fiber growth. They must incorporate conductivity to allow electrode sites to connect with external circuitry and electrical properties and be tuned to transmit neural signals.
In another prosthetics research effort, the Oak Ridge National Laboratory (ORNL) managed by UT Battelle for the Department of Energy is helping soldiers who have lost a leg by using technology to improve prosthesis fitting and design. ORNL biomedical engineers are perfecting a portable wearable system to measure walking patterns that can be applied to real-world activities in a variety of settings. The work is being done in collaboration with the Center for the Intrepid at Brooke Army Medical Center (BAMC).
If the prosthetic does not fit properly or not aligned correctly, it can affect a patient’s walking patterns, resulting in “asymmetric” gait. These abnormal gait patterns can increase the stress on the healthy limb, leading to problems later in life such as arthritis.
To monitor the motion and force of walking patterns, the researchers at BAMC are using Inertial Measurement Units (IMU) and other sensors that can be strapped into segments of a subject’s leg, such as the thigh, calf, and foot. The data collected from the IMUs is transferred to a computer where the algorithms are then able to calculate the motions and forces associated with specific joints.
To test the effectiveness of IMUs, a robot leg has been programmed with data from a walking person. In a few months, they plan to test their system on a human subject with a prosthetic and healthy leg.