Running head: NEUROMECHANICAL APPLICATIONS IN PROSTHETICS 1 Neuromechanical Applications in Intelligent Prosthetics All group members listed below contributed to the writing and/or editing of the following document. Mollie Kowalchik ____________________________________________ Derek Crowe ____________________________________________ Micaela Austin ____________________________________________ Kareem Mohamed ____________________________________________ Courtney Sullivan ____________________________________________ Caroline McCarthy ____________________________________________ Alex Mercurio ____________________________________________NEUROMECHANICAL APPLICATIONS IN PROSTHETICS 2 The field of neuromechanics combines biomechanics and motor control. Biomechanics and motor control are both fields that look into human’s muscles and movements. Motor control is generally defined as one’s ability to direct and activate muscles and movements. It involves the Central Nervous System (CNS) consisting of the spinal cord, brain stem, cortex and cerebellum, and the Peripheral Nervous System (PNS) also known as the sensory system. Motor control research involves investigating how these systems create coordinated movements in the body when in contact with the environment. The goal of motor control is to be able to assess and evaluate motor deficiencies and performance (Latash, 2010). Biomechanics is defined as many scientific disciplines that define and record human movement. It examines the internal and external forces that act on the human body and the effects of these forces. Biomechanics has both a kinematics and kinetics branch. Kinematics involves the study of movement in space or geometrical point of view, while kinetics is study of what causes the body to move the way it does. Researchers use quantitative methods for comparisons (Winter, 2009). Prosthetics are an artificial substitution of a missing limb. Losing a limb causes the loss of both motor and sensory function. These losses result in a disability with possibly enormous consequences for activities of daily living and quality of life. There are two types of prosthetics: regular prosthetics and advanced prosthetics (Schmalzl et al., 2014). Regular prosthetics are body-powered. This means that a person uses their own body movements to control the prosthetic. A Bowden cable is used to transfer the forces created by the body movements to an end device (Schmalzl et al., 2014). Advanced prosthetics are battery-powered. There is certain criteria that needs to be met for a prosthetic to be considered advanced. It must be able to perform fine voluntary motor commands and be able to supply the user with detailed sensory feedback (Schmalzl et al., 2014). This sensory feedback involves the recorded stimulus being transferred and translated through a different sensory channel than which is normally used. This allows the body to receive sensory information (Antfolk et al., 2013). One of the most critical aspects of a powered prosthetic device is its integration with the user’s own nervous system. The nervous system is responsible for the execution of voluntaryNEUROMECHANICAL APPLICATIONS IN PROSTHETICS 3 motor tasks in our body and the communication of sensory feedback. The question is; how can we use motor control in prosthetics? In general, there are three main methods of integrating nervous impulses into a prosthetic system: myoelectric control, targeted muscle innervation, and neural interface. All of these systems allow for motor commands to be transmitted based off of neural signals themselves, with each allowing for different types and numbers of movements. Advancements in these control methods, particularly with neural interfaces, will greatly increase the capabilities of robotic prostheses in the near future. Myoelectric control is a method that uses electromyographic (EMG) signals from the local skeletal muscles as a source for motor commands and to execute motor tasks (Geethanjali, 2016). EMGs, or the electrical impulses generated by the existing nerves in our muscles, are detected and relayed by a series of electrodes and sensors connected to the device. These can be placed on the surface of the skin, which is less invasive, or directly implanted in the muscles themselves, which is more invasive, but allows for better communication. These signals then go through a control scheme, or a pathway that deciphers data from the EMGs, such as amplitude, and translates them into a motor action for the prosthetic device. There are numerous variants of these control schemes, depending on the type of myoelectric device. Examples of control schemes described by Geethanjali (2016) include: on/off controls, which turn on a motor after amplitude is analyzed against a certain threshold, proportional controls, which use voltage to control the speed of movement, and pattern recognition controls, which use recognized EMG patterns to predict intended movement. Myoelectric controls are a widely used method of neural integration in powered prosthesis. Targeted Muscle Innervation is a surgical method often used to enhance myoelectric control methods and increase the quantity and quality of possible movements. In this technique, which is most commonly used in amputees, nerves from the amputated limb are removed and are reinnervated onto a different muscle in its proximity. For example, nerves are often reinnervated onto the pectoralis major muscle in upper limb amputations. This has two functions: first, the EMG signals used are now biologically amplified (Cheesborough et al., 2015), allowing for quicker, more accurate transfers of information, and secondly, it adds more sources of EMG signals that can be used to control a prosthetic device. This results in smoother, more accurate,NEUROMECHANICAL APPLICATIONS IN PROSTHETICS 4 and more intuitive control of prosthetic motions, as well as more possible movements in general (Cheesborough et al., 2015). Reinnervated nerves can provide more complex and reliable outputs that can be used for more possible movements than in standard myoelectric control mechanisms. While this technique is incredibly invasive, the benefits of this procedure are tremendous, especially coupled with the right myoelectric control schemes. While the previous methods have done much to advance the functionality of powered prosthetics, neural interface systems (NIS) have brought