395 JRRD JRRD Volume 50, Number 3, 2013 Pages 395–408 Selection of muscle and nerve-cuff electrodes for neuroprostheses using customizable musculoskeletal model Dimitra Blana, PhD; 1–2 Juan G. Hincapie, PhD; 1 Edward K. Chadwick, PhD; 1–2* Robert F. Kirsch, PhD 1,3 1 Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH; 2 Department of Sport and Exercise Science, Aberystwyth University, Aberystwyth, UK; 3 Louis Stokes Cleveland Department of Veterans Affairs Medical Center, Cleveland, OH Abstract—Neuroprosthetic systems based on functional elec- trical stimulation aim to restore motor function to individuals with paralysis following spinal cord injury. Identifying the optimal electrode set for the neuroprosthesis is complicated because it depends on the characteristics of the individual (such as injury level), the force capacities of the muscles, the movements the system aims to restore, and the hardware limi- tations (number and type of electrodes available). An elec- trode-selection method has been developed that uses a customized musculoskeletal model. Candidate electrode sets are created based on desired functional outcomes and the hard- ware limitations of the proposed system. Inverse-dynamic simu- lations are performed to determine the proportion of target movements that can be accomplished with each set; the set that allows the most movements to be performed is chosen as the optimal set. The technique is demonstrated here for a system recently developed by our research group to restore whole-arm movement to individuals with high-level tetraplegia. The opti- mal set included selective nerve-cuff electrodes for the radial and musculocutaneous nerves; single-channel cuffs for the axillary, suprascapular, upper subscapular, and long-thoracic nerves; and muscle-based electrodes for the remaining channels. The importance of functional goals, hardware limitations, mus- cle and nerve anatomy, and surgical feasibility are highlighted. Key words: functional electrical stimulation, muscle elec- trode, musculoskeletal model, nerve-cuff electrode, neuropros- thesis, rehabilitation, shoulder, simulation, spinal cord injury, upper limb. INTRODUCTION Neuroprostheses restore motor function after spinal cord injury (SCI) by applying functional electrical stimu- lation (FES) to paralyzed muscles. The number of mus- cles targeted by the FES system is a function not only of the level of injury, which determines the extent of the paralysis, but also of the number of stimulation channels available in the neuroprosthesis itself. For example, arm function in low tetraplegia (cervical [C]7 SCI) can be sig- nificantly improved with stimulation of just the triceps [1], because most of the other arm muscles are under vol- untary control. However, in the same population, all hand muscles are typically paralyzed and FES systems that restore basic hand function (i.e., grasp and release) use at least eight stimulating channels [2]. Restoring more natural and dexterous hand function would require many more channels than the current neuroprostheses can provide [3]. In this case, it is the availability of stimulating channels Abbreviations: C = cervical, EMG = electromyography, FES = functional electrical stimulation, LED = light emitting diodes, SCI = spinal cord injury. * Address all correspondence to Edward K. Chadwick, PhD; Institute for Science and Technology in Medicine, Guy Hilton Research Centre, Keele University, Thornburrow Drive, Stoke-on-Trent, ST4 7QB, UK; +44-1782-554600. Email: e.k.j.chadwick@keele.ac.uk http://dx.doi.org/10.1682/JRRD.2012.02.0034