FRONTIERS Recapitulating Flesh with Silicon and Steel: Advancements in Upper Extremity Robotic Prosthetics Brian Lee 1 , Frank J. Attenello 1 , Charles Y. Liu 1 , Michael P. McLoughlin 2 , Michael L. J. Apuzzo 1 With the loss of function of an upper extremity because of stroke or spinal cord injury or a physical loss from ampu- tation, an individual’s life is forever changed, and activities that were once routine become a magnitude more difficult. Much research and effort have been put into developing advanced robotic prostheses to restore upper extremity function. For patients with upper extremity amputations, previously crude prostheses have evolved to become exceptionally functional. Because the upper extremities can perform a wide variety of activities, several types of upper extremity prostheses are available ranging from passive cosmetic limbs to externally powered robotic limbs. In addition, new developments in brain-machine interface are poised to revolutionize how patients can control these advanced prostheses using their thoughts alone. For patients with spinal cord injury or stroke, functional electrical stimulation promises to provide the most sophisticated prosthetic limbs possible by reanimat- ing paralyzed arms of these patients. Advances in tech- nology and robotics continue to help patients recover vital function. This article examines the latest neurorestorative technologies for patients who have either undergone amputation or lost the use of their upper extremities sec- ondary to stroke or spinal cord injury. INTRODUCTION There is nothing quite like the upper extremity, from arm to hand to fingertip, which allows us to interact with the world in a manner that is so uniquely human. Our 2 upper extremities allow us to perform amazing feats, such as playing a piano concerto, building skyscrapers, and performing delicate surgery on the brain. There is tremendous iconography that surrounds the arms and hands that can be appreciated in paintings, sculptures, and film. It is understandably devastating when individuals experience loss of function of an upper extremity as a result of stroke or spinal cord injury (SCI) or a physical loss from amputation. Lives are forever changed, and activities that were previously routine become a magnitude more difficult. These patients work tirelessly with physical and occupational therapists to rehabilitate their remaining function and learn new techniques and strategies to perform necessary activities of daily living (ADLs). More recent advances in technology and robotics have resulted in tremendous progress in restoring function in these patients. Ro- bots, especially robotic limbs—as seen in popular films such as Star Wars, Robocop, and Terminator—have captured our imaginations and come to symbolize the promise the future holds with advancing technology. New developments in brain-machine interface are poised to revolutionize how patients can control sophisticated prostheses using their thoughts alone (43). In this article, we examine the latest technologies for patients who have either un- dergone amputation or lost use of their upper extremities. Key words - Arm - Brain-machine interface - Limb - Prosthetic - Robotic - Upper extremity Abbreviations and Acronyms ADLs: Activities of daily living DOF: Degrees of freedom ECoG: Electrocorticography EEG: Electroencephalography EMG: Electromyography FES: Functional electrical stimulation IMU: Inertial measurement units MPL: Modular Prosthetic Limb SCI: Spinal cord injury TMR: Targeted muscle reinnervation From the 1 Department of Neurosurgery, University of Southern California, Los Angeles, California; and 2 The Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland, USA To whom correspondence should be addressed: Brian Lee, M.D., Ph.D. [E-mail: brianlee@usc.edu] Citation: World Neurosurg. (2014) 81, 5/6:730-741. http://dx.doi.org/10.1016/j.wneu.2014.03.012 Journal homepage: www.WORLDNEUROSURGERY.org Available online: www.sciencedirect.com 1878-8750/$ - see front matter ª 2014 Elsevier Inc. All rights reserved. 730 www.SCIENCEDIRECT.com WORLD NEUROSURGERY, http://dx.doi.org/10.1016/j.wneu.2014.03.012 PEER-REVIEW REPORTS: FRONTIERS