A new prosthetic arm operated by a wounded soldier at the Walter Reed National Military Medical Center (WRNMMC) for the first time, enabled the soldier to control the device’s metallic fingers and wrist with his thoughts. The Modular Prosthetic Limb (MPL) was developed as part of a four year research program by the Johns Hopkins University Applied Physics Laboratory, WRNMMC, and the Uniformed Services University of the Health Sciences (USU).
Col. (Dr.) Paul Pasquina, Chief of Orthopedics and Prosthetics at WRNMMC and Director for the Center of Rehabilitation Sciences at USU explained that the limb is controlled by surface electrodes that pick up electric signals generated by the muscles underneath the skin, and then convert those patterns in electrical signals into a robotic function.
With an amputee, the nerves traveling down the spinal cord are still intact, and they’re still connected to some of the muscles in the arm, said Pasquina. “What we are trying to do is pick up the electrical signals of the muscles that still exist in the arm and then interpret and convert these signals to a computer signal that will then drive a robotic limb. For example, when an individual is thinking about closing their hand, muscles will activate and the prosthetic limb will respond accordingly.”
As Cmdr. Jack Tsao, Director, Traumatic Brain Injury Programs for Navy Medicine’s Bureau of Medicine and Surgery explained, before being fitted with the device, amputees must first go through training using the Virtual Integrated Environment (VIE) to record their muscle movements. By collecting the amputees muscle data, the MPL is then individualized for the person using the device.
Engineers are hoping to use electrodes underneath the skin to achieve an electrical signal with much higher fidelity. Researchers are looking to explore other mechanisms to rewire nerves and learn even more about how the body can integrate with computers and computer interface. “The next step in MPL’s development is to incorporate sense of touch and apply this technology to prosthetic legs in the future”, said Tsao.