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Individuals with upper extremity (UE) amputation abandon prostheses due to challenges with significant device weight—particularly among myoelectric prostheses—and limited device dexterity, durability, and reliability among both myoelectric and body-powered prostheses. The Modular Prosthetic Limb (MPL) system couples an advanced UE prosthesis with a pattern recognition paradigm for intuitive, non-invasive prosthetic control. Pattern recognition accuracy and functional assessment—Box & Blocks (BB), Jebsen-Taylor Hand Function Test (JHFT), and Assessment of Capacity for Myoelectric Control (ACMC)—scores comprised the main outcomes. 10 participants were included in analyses, including seven individuals with traumatic amputation, two individuals with congenital limb absence, and one with amputation secondary to malignancy. The average (SD) time since limb loss, excluding congenital participants, was 85.9 (59.5) months. Participants controlled an average of eight motion classes compared to three with their conventional prostheses. All participants made continuous improvements in motion classifier accuracy, pathway completion efficiency, and MPL manipulation. BB and JHFT improvements were not statistically significant. ACMC performance improved for all participants, with mean (SD) scores of 162.6 (105.3), 213.4 (196.2), and 383.2 (154.3), p = 0.02 between the baseline, midpoint, and exit assessments, respectively. Feedback included lengthening the training period to further improve motion classifier accuracy and MPL control. The MPL has potential to restore functionality to individuals with acquired or congenital UE loss.

In this work, we investigated the use of noninvasive, targeted transcutaneous electrical nerve stimulation (TENS) of peripheral nerves to provide sensory feedback to two amputees, one with targeted sensory reinnervation (TSR) and one without TSR. A major step in developing a closed-loop prosthesis is providing the sense of touch back to the amputee user. We investigated the effect of targeted nerve stimulation amplitude, pulse width, and frequency on stimulation perception. We discovered that both subjects were able to reliably detect stimulation patterns with pulses less than 1 ms. We utilized the psychophysical results to produce a subject specific stimulation pattern using a leaky integrate and fire (LIF) neuron model from force sensors on a prosthetic hand during a grasping task. For the first time, we show that TENS is able to provide graded sensory feedback at multiple sites in both TSR and non-TSR amputees while using behavioral results to tune a neuromorphic stimulation pattern driven by a force sensor output from a prosthetic hand.

Injury due to underbody loading is increasingly relevant to the safety of the modern warfighter. To accurately evaluate injury risk in this loading modality, a biofidelic anthropomorphic test device (e.g., dummy) is required. Finite element model counterparts to the physical dummies are also useful tools in the evaluation of injury risk, but require validated constitutive material models used in the dummy. However, material model fitting can result in models that are over-fit: they match well with the data they were trained on, but do not extrapolate well to new loading scenarios. In this study, we used a hierarchical approach. Material models created from coupon-level tests were evaluated at the component level, and then verified using blinded component and whole body (WB) tests to establish a material model of the anthropomorphic test device (ATD) neck that was not over-fit. Additionally, a combined metric is introduced that incorporates the well-known correlation analysis (CORA) score with peak characteristics to holistically evaluate the material model performance. A Bergstrom Boyce material model fit to one loop of combined compression and tension experimental data performed the best within the training datasets. Its combined metric scores were 2.51 and 2.18 (max score of 3) in a constrained neck and head neck setup, respectively. In the blinded evaluation including flexed, extended, and WB simulations, similar combined scores were observed with 2.44, 2.26, and 2.60, respectively. The agreement between the combined scores in the training and validation dataset indicated that model was not over-fit and can be extrapolated into untested, but similar loading scenarios.

Objective.Full restoration of arm function using a prosthesis remains a grand challenge; however, advances in robotic hardware, surgical interventions, and machine learning are bringing seamless human-machine interfacing closer to reality.Approach.Through extensive data logging over 1 year, we monitored at-home use of the dexterous Modular Prosthetic Limb controlled through pattern recognition of electromyography (EMG) by an individual with a transhumeral amputation, targeted muscle reinnervation, and osseointegration (OI).Main results.Throughout the study, continuous prosthesis usage increased (1% per week,p< 0.001) and functional metrics improved up to 26% on control assessments and 76% on perceived workload evaluations. We observed increases in torque loading on the OI implant (up to 12.5% every month,p< 0.001) and prosthesis control performance (0.5% every month,p< 0.005), indicating enhanced user integration, acceptance, and proficiency. More importantly, the EMG signal magnitude necessary for prosthesis control decreased, up to 34.7% (p< 0.001), over time without degrading performance, demonstrating improved control efficiency with a machine learning-based myoelectric pattern recognition algorithm. The participant controlled the prosthesis up to one month without updating the pattern recognition algorithm. The participant customized prosthesis movements to perform specific tasks, such as individual finger control for piano playing and hand gestures for communication, which likely contributed to continued usage.Significance.This work demonstrates, in a single participant, the functional benefit of unconstrained use of a highly anthropomorphic prosthetic limb over an extended period. While hurdles remain for widespread use, including device reliability, results replication, and technical maturity beyond a prototype, this study offers insight as an example of the impact of advanced prosthesis technology for rehabilitation outside the laboratory.

Impact biomechanics research in occupant safety predominantly focuses on the effects of loads applied to human subjects during automotive collisions. Characterization of the biomechanical response under such loading conditions is an active and important area of investigation. However, critical knowledge gaps remain in our understanding of human biomechanical response and injury tolerance under vertically accelerated loading conditions experienced due to underbody blast (UBB) events. This knowledge gap is reflected in anthropomorphic test devices (ATDs) used to assess occupant safety. Experiments are needed to characterize biomechanical response under UBB relevant loading conditions. Matched pair experiments in which an existing ATD is evaluated in the same conditions as a post mortem human subject (PMHS) may be utilized to evaluate biofidelity and injury prediction capabilities, as well as ATD durability, under vertical loading. To characterize whole body response in the vertical direction, six whole body PMHS tests were completed under two vertical loading conditions. A series of 50th percentile hybrid III ATD tests were completed under the same conditions. Ability of the hybrid III to represent the PMHS response was evaluated using a standard evaluation metric. Tibial accelerations were comparable in both response shape and magnitude, while other sensor locations had large variations in response. Posttest inspection of the hybrid III revealed damage to the pelvis foam and skin, which resulted in large variations in pelvis response. This work provides an initial characterization of the response of the seated hybrid III ATD and PMHS under high rate vertical accelerative loading.

Objective. Validating the ability for advanced prostheses to improve function beyond the laboratory remains a critical step in enabling long-term benefits for prosthetic limb users. Approach. A nine week take-home case study was completed with a single participant with upper limb amputation and osseointegration to better understand how an advanced prosthesis is used during daily activities. The participant was already an expert prosthesis user and used the Modular Prosthetic Limb (MPL) at home during the study. The MPL was controlled using wireless electromyography (EMG) pattern recognition-based movement decoding. Clinical assessments were performed before and after the take-home portion of the study. Data was recorded using an onboard data log in order to measure daily prosthesis usage, sensor data, and EMG data. Main results. The participant’s continuous prosthesis usage steadily increased (p= 0.04, max = 5.5 h) over time and over 30% of the total time was spent actively controlling the prosthesis. The duration of prosthesis usage after each pattern recognition training session also increased over time (p = 0.04), resulting in up to 5.4 h of usage before retraining the movement decoding algorithm. Pattern recognition control accuracy improved (1.2% per week, p < 0.001) with a maximum number of ten classes trained at once and the transitions between different degrees of freedom increased as the study progressed, indicating smooth and efficient control of the advanced prosthesis. Variability of decoding accuracy also decreased with prosthesis usage (p < 0.001) and 30% of the time was spent performing a prosthesis movement. During clinical evaluations, Box and Blocks and the Assessment of the Capacity for Myoelectric Control scores increased by 43% and 6.2%, respectively, demonstrating prosthesis functionality and the NASA Task Load Index scores decreased, on average, by 25% across assessments, indicating reduced cognitive workload while using the MPL, over the nine week study. Significance. In this case study, we demonstrate that an onboard system to monitor prosthesis usage enables better understanding of how prostheses are incorporated into daily life. That knowledge can support the long-term goal of completely restoring independence and quality of life to individuals living with upper limb amputation.

The experimental measurement of biomechanical responses that correlate with blast-induced traumatic brain injury (bTBI) has proven challenging. These data are critical for both the development and validation of computational and physical head models, which are used to quantify the biomechanical response to blast as well as to assess fidelity of injury mitigation strategies, such as personal protective equipment. Therefore, foundational postmortem human surrogate (PMHS) experimental data capturing the biomechanical response are necessary for human model development. Prior studies have measured short-duration pressure transmission to the brain (Kinetic phase), but have failed to reproduce and measure the longer-duration inertial loading that can occur (Kinematic phase). Four fully instrumented PMHS were subjected to short-duration dynamic overpressure in front-facing and rear-facing orientations, where intracranial pressure (ICP), global head kinematics, and brain motion (as measured by high-speed X-ray) with respect to the skull were recorded. Peak ICP results generally increased with increased dose, and a mirrored pressure response was seen when comparing the polarity of frontal bone versus occipital bone ICP sensors. The head kinematics were delayed when compared to the pressure response and showed higher peak angles for front-facing tests as compared to rear-facing. Brain displacements were approximately 2–6 mm, and magnitudes did not change appreciably between front- and rear-facing tests. These data will be used to inform and validate models used to assess bTBI.

Revolutionizing Prosthetics is a government-sponsored program focused on maturing the many foundational technologies that comprise neural prosthetic systems. Targeting the needs of amputees and movement-impaired individuals, the program focused on technological advancements in areas such as advanced neural recording devices, neural decoding and encoding algorithms, and upper limb prosthetic systems. A primary objective of the program was to support technological advancement of wearable prosthetic devices at the upper limb and hand level. The Modular Prosthetic Limb (MPL) is a representation of the vision for a highly anthropometric prosthetic limb. With 26 articulating joints, 17 actuators, and hundreds of internal sensors for feedback, the vision of the MPL was to replicate the dexterity, speed, and strength of the human hand to an extent never realized in a prosthetic device. Here we describe the MPL’s evolution over the past 13 years and describe the system in entirety, focusing on the fundamental characteristics of the system from hardware to software and controls. Additionally, we briefly touch upon some clinical applications and alternative use cases for the system to date.

ObjectiveA major challenge for controlling a prosthetic arm is communication between the device and the user’s phantom limb. We show the ability to enhance amputees’ phantom limb perception and improve movement decoding through targeted transcutaneous electrical nerve stimulation (tTENS).ApproachTranscutaneous nerve stimulation experiments were performed with four amputee participants to map phantom limb perception. We measured myoelectric signals during phantom hand movements before and after amputees received sensory stimulation. Using electroencephalogram (EEG) monitoring, we measure the neural activity in sensorimotor regions during phantom movements and stimulation. In one participant, we also tracked sensory mapping over 2 years and movement decoding performance over 1 year.Main resultsResults show improvements in the amputees’ ability to perceive and move the phantom hand as a result of sensory stimulation, which leads to improved movement decoding. In the extended study with one amputee, we found that sensory mapping remains stable over 2 years. Remarkably, sensory stimulation improves within-day movement decoding while performance remains stable over 1 year. From the EEG, we observed cortical correlates of sensorimotor integration and increased motor-related neural activity as a result of enhanced phantom limb perception.SignificanceThis work demonstrates that phantom limb perception influences prosthesis control and can benefit from targeted nerve stimulation. These findings have implications for improving prosthesis usability and function due to a heightened sense of the phantom hand.

Background: Despite advances in prosthetic development and neurorehabilitation, individuals with upper extremity (UE) loss continue to face functional and psychosocial challenges following amputation. Recent advanced myoelectric prostheses offer intuitive control over multiple, simultaneous degrees of motion and promise sensory feedback integration, but require complex training to effectively manipulate. We explored whether a virtual reality simulator could be used to teach dexterous prosthetic control paradigms to individuals with UE loss. Methods: Thirteen active-duty military personnel with UE loss (14 limbs) completed twenty, 30-min passive motor training sessions over 1–2 months. Participants were asked to follow the motions of a virtual avatar using residual and phantom limbs, and electrical activity from the residual limb was recorded using surface electromyography. Eight participants (nine limbs), also completed twenty, 30-min active motor training sessions. Participants controlled a virtual avatar through three motion sets of increasing complexity (Basic, Advanced, and Digit) and were scored on how accurately they performed requested motions. Score trajectory was assessed as a function of time using longitudinal mixed effects linear regression. Results: Mean classification accuracy for passive motor training was 43.8 ± 10.7% (14 limbs, 277 passive sessions). In active motor sessions, >95% classification accuracy (which we used as the threshold for prosthetic acceptance) was achieved by all participants for Basic sets and by 50% of participants in Advanced and Digit sets. Significant improvement in active motor scores over time was observed in Basic and Advanced sets (per additional session: β-coefficient 0.125, p = 0.022; β-coefficient 0.45, p = 0.001, respectively), and trended toward significance for Digit sets (β-coefficient 0.594, p = 0.077). Conclusions: These results offer robust evidence that a virtual reality training platform can be used to quickly and efficiently train individuals with UE loss to operate advanced prosthetic control paradigms. Participants can be trained to generate muscle contraction patterns in residual limbs that are interpreted with high accuracy by computer software as distinct active motion commands. These results support the potential viability of advanced myoelectric prostheses relying on pattern recognition feedback or similar controls systems.

This chapter presents a biomechanical guidance navigation system for performing periacetabular osteotomy (PAO) to treat developmental dysplasia of the hip. The main motivation of the biomechanical guidance system (BGS) is to plan and track the osteotomized fragment in real time during PAO while simplifying this challenging procedure. The BGS computes the three-dimensional position of the osteotomized fragment in terms of conventional anatomical angles and simulates biomechanical states of the joint. This chapter describes the BGS structure and its application using two different navigation approaches including optical tracking of the fragment and x-ray-based navigation. Both cadaver studies and preliminary clinical studies showed that the biomechanical planning is consistent with traditional PAO planning techniques and that the additional information provided by accurate 3D positioning of the fragment does not adversely impact the surgery.

Underbody Blast (UBB) events subject vehicle occupants to large accelerations that often result in severe lumbar spine injury. Little knowledge exists on the intervertebral disc response during high-rate vertical accelerative loading. To address this gap, the current study investigates intradiscal pressures under UBB loading utilizing biomechanical testing from: 1) isolated Post Mortem Human Surrogate (PMHS) lumbar spine motion segments (LMS) in a custom-designed drop tower fixture; and 2) whole body (WHBO) PMHS in a custom-designed Vertically Accelerated Load Transfer System. During testing, intradiscal pressures were comparable between the LMS and WHBO tests, with non-fracture cases producing higher average peak pressures than fractured tests. Additionally, WHBO testing demonstrated that upper body posture can influence lumbar pressure responses. The current study evaluates lumbar intradiscal pressure transduction as it relates to vertebral fracture in both component and whole body experiments.Copyright © 2016 by ASME

This report describes the development, testing, and finite element model (FEM) of the Warrior Injury Assessment Manikin (WIAMan) Anthropomorphic Test Device (ATD) Lumbar Spine Materials Demonstrator. A primary objective of this work was to generate experimental data for FEM validation and to create lumbar spine demonstrators that were used to characterize candidate materials to assess the effect of material type and hardness for the lumbar spine ATD component. Several rubber chemistries and hardnesses were used for the compliant elements of the lumbar spine demonstrators. The material demonstrators were tested under dynamic loading using the Medical College of Wisconsin vertical accelerator test machine. The responses of the different lumbar spine demonstrators were compared with the biofidelic response corridors to assess the levels of biofidelity of the WIAMan ATD lumbar spine design.

Background: Researchers have found it difficult to recreate a Lauge-Hansen supination-external rotation-type ankle fracture in experimental settings. We hypothesized that a pronation-external rotation mechanism could cause both distal, short oblique and high fibular fractures and that the fracture type would be affected by associated, laterally directed forces applied to the foot. Methlods: Twenty-three cadaver ankles were subjected to fracture loading that replicated the Lauge-Hansen pronation-external rotation mechanism with or without applying an external lateral force. In Phase I, an axial load was applied to fifteen specimens mounted on a materials testing machine. Each foot was rotated externally to failure. In Phase II, eight specimens were tested according to the Phase-I protocol, but external forces were applied laterally at the foot to increase the abduction moment at the ankle. Load and position versus time curves were recorded and were correlated with video image data to establish the sequence of failure of specific anatomic structures. Results: Eight specimens tested in Phase I sustained an oblique fracture of the distal end of the fibula with both medial and posterior injuries that occurred after the fibular fracture. Increasing the external lateral force and hence the abduction moment within the ankle (Phase II) resulted in three of eight specimens sustaining a high fibular fracture with a reversed fracture line (anterosuperior to posteroinferior) and/or a comminuted high fibular fracture. The distribution of traditional pronation-external rotation-type fractures differed significantly between Phase I and Phase II (p = 0.032). Conclusions: This study generated counterexamples to the Lauge-Hansen classification system by showing that a short oblique fracture of the distal end of the fibula can occur with the foot in the pronated position. Furthermore, a high fibular fracture was recreated by increasing the abduction moment at the ankle. Clinical Relevance: The pattern of ankle fracture is related directly to the applied loads, including specifically the combination of the external rotational moment and the abduction moment. The results of the current study could provide the basis for a more straightforward classification of ankle fractures based on applied loads.

Our goal was to quantify and visualize the three-dimensional loading relationship between the ligaments and articular surfaces of the ankle to identify and determine the stabilizing roles of these anatomical structures during the stance phase of gait.We applied discrete element analysis to computationally model the three-dimensional contact characteristics and ligament loading of the ankle joint. Physiologic loads approximating those at five positions in the stance phase of a normal walk cycle were applied. We analyzed joint contact pressures and periankle ligament tension concurrently.Most ankle joint loading during the stance phase occurred across the articular surfaces of the joint, and the amount of ligament tension was small. The tibiotalar articulation showed full congruency throughout most of the stance phase, with peak pressure developing anteriorly toward the toe-off frame. Of the periankle ligaments, the deep deltoid ligament transferred the most force during the stance phase (57.2%); the superficial deltoid ligament transferred the second-most force (26.1%). The anterior talofibular ligament transferred force between the talus and fibula continuously, whereas the calcaneofibular ligament did not carry force during gait. The distal tibiofibular ligaments and the interosseous membrane were loaded throughout the stance phase.Force transmission through the ankle joint during the stance phase is predominantly through the articular surfaces, and the periankle ligaments do not play a major stabilizing role in constraining ankle motion. The medial ligaments have a more important role than do the lateral ligaments in stabilizing the ankle joint.In addition to ligament insufficiency, other factors, such as varus tilt of the tibial plafond, may be important in the development of recurrent instability. Continuous loading of syndesmosis ligaments provides a theoretical basis for evidence of syndesmosis screw breakage or loosening. The analysis method has potential applications for clarifying ankle joint function and providing a basis for comparison between normal and abnormal joint conditions.

Background and purpose Because of the varying structure of dysplastic hips, the optimal realignment of the joint during periacetabular osteotomy (PAO) may differ between patients. Three-dimensional (3D) mechanical and radiological analysis possibly accounts better for patient-specific morphology, and may improve and automate optimal joint realignment. Patients and methods We evaluated the 10-year outcomes of 12 patients following PAO. We compared 3D mechanical analysis results to both radiological and clinical measurements. A 3D discrete-element analysis algorithm was used to calculate the pre- and postoperative contact pressure profile within the hip. Radiological angles describing the coverage of the joint were measured using a computerized approach at actual and theoretical orientations of the acetabular cup. Quantitative results were compared using postoperative clinical evaluation scores (Harris score), and patient-completed outcome surveys (q-score) done at 2 and 10 years. Results The 3D mechanical analysis indicated that peak joint contact pressure was reduced by an average factor of 1.7 subsequent to PAO. Lateral coverage of the femoral head increased in all patients; however, it did not proportionally reduce the maximum contact pressure and, in 1 case, the pressure increased. This patient had the lowest 10-year q-score (70 out of 100) of the cohort. Another hip was converted to hip arthroplasty after 3 years because of increasing osteoarthritis. Interpretation The 3D analysis showed that a reduction in contact pressure was theoretically possible for all patients in this cohort, but this could not be achieved in every case during surgery. While intraoperative factors may affect the actual surgical outcome, the results show that 3D contact pressure analysis is consistent with traditional PAO planning techniques (more so than 2D analysis) and may be a valuable addition to preoperative planning and intraoperative assessment of joint realignment.

Objective. We used native sensorimotor representations of fingers in a brain–machine interface (BMI) to achieve immediate online control of individual prosthetic fingers. Approach. Using high gamma responses recorded with a high-density electrocorticography (ECoG) array, we rapidly mapped the functional anatomy of cued finger movements. We used these cortical maps to select ECoG electrodes for a hierarchical linear discriminant analysis classification scheme to predict: (1) if any finger was moving, and, if so, (2) which digit was moving. To account for sensory feedback, we also mapped the spatiotemporal activation elicited by vibrotactile stimulation. Finally, we used this prediction framework to provide immediate online control over individual fingers of the Johns Hopkins University Applied Physics Laboratory modular prosthetic limb. Main results. The balanced classification accuracy for detection of movements during the online control session was 92% (chance: 50%). At the onset of movement, finger classification was 76% (chance: 20%), and 88% (chance: 25%) if the pinky and ring finger movements were coupled. Balanced accuracy of fully flexing the cued finger was 64%, and 77% had we combined pinky and ring commands. Offline decoding yielded a peak finger decoding accuracy of 96.5% (chance: 20%) when using an optimized selection of electrodes. Offline analysis demonstrated significant finger-specific activations throughout sensorimotor cortex. Activations either prior to movement onset or during sensory feedback led to discriminable finger control. Significance. Our results demonstrate the ability of ECoG-based BMIs to leverage the native functional anatomy of sensorimotor cortical populations to immediately control individual finger movements in real time.

Effective user control of highly dexterous and robotic assistive devices requires intuitive and natural modalities. Although surgically implanted brain-computer interfaces (BCIs) strive to achieve this, a number of non-invasive engineering solutions may provide a quicker path to patient use by eliminating surgical implantation. We present the development of a semi-autonomous control system that utilizes computer vision, prosthesis feedback, effector centric device control, smooth movement trajectories, and appropriate hand conformations to interact with objects of interest. Users can direct a prosthetic limb through an intuitive graphical user interface to complete multi-stage tasks using patient appropriate combinations of control inputs such as eye tracking, conventional prosthetic controls/joysticks, surface electromyography (sEMG) signals, and neural interfaces (ECoG, EEG). Aligned with activities of daily living (ADL), these tasks include directing the prosthetic to specific locations or objects, grasping of objects by modulating hand conformation, and action upon grasped objects such as self-feeding. This Hybrid Augmented Reality Multimodal Operation Neural Integration Environment (HARMONIE) semi-autonomous control system lowers the user's cognitive load, leaving the bulk of command and control of the device to the computer. This flexible and intuitive control system could serve patient populations ranging from wheelchair-bound quadriplegics to upper-limb amputees.

We explored the use of the Virtual Integrated Environment (VIE), developed by the Johns Hopkins University Applied Physics Lab (JHU/APL), in treating phantom limb pain in seven upper-extremity amputees. Further, we tested pattern recognition control of a virtual avatar using surface electromyography signals captured from subjects' residual limbs. The majority of patients responded to treatment, reporting decreased pain intensity and symptoms. Six of seven subjects showed greater than eighty percent classification accuracies for at least seven motion classes. After successfully operating the VIE, one subject underwent preliminary testing with an advanced myoelectric prosthesis, the Modular Prosthetic Limb, also developed by JHU/APL.

This paper details a method for tracking 3D kinematics of the skull and brain deformation in post-mortem human subjects (PMHS) using 2D cineradiographic images during a high-rate loading event. Brain displacement and resulting strain due to blast loading is a metric for Traumatic Brain Injury (TBI), however physically measuring brain motion experimentally is a significant challenge. A shock tube, used to simulate blast exposure, created skull and brain motion tracked using implanted radio-opaque markers and high-speed X-ray images. These images were registered to a computed tomography (CT) scan using intensity-based 2D-3D registration techniques. To register the 2D images to the 3D scan, digitally reconstructed radiographs were generated from the CT scan, and then compared to the recorded x-ray frames by maximizing similarity metrics between the images using a Covariance Matrix Adaptation Evolution Strategy. As compared to pure 2D tracking, 2D-3D registration provides out-of-plane kinematics by fully leveraging information in the x-ray projection image and prior information from the 3D CT scan. Data generated with these techniques are critical for physically understanding the mechanisms associated with blast exposure that may lead to TBI, and can be used for human computational model validation.

Traumatic Brain Injury (TBI) has been the termed the “signature injury” in wounded soldiers in recent military operations [1]. Evidence has shown a strong association between TBI and blast loading to the head due to exposure to explosive events [2, 3]. Head injury mechanisms in a primary blast environment remain elusive and are the subject of much speculation and hypotheses. However, brain injury mechanisms have traditionally been attributed to either a direct impact or a rapid head acceleration or deceleration. Extensive research has been performed regarding the effects of blunt trauma and inertial loading on head injuries [4, 5]. Direct impacts to the head can largely be described based on linear acceleration measurements that correlate to skull fracture and focal brain injuries [6]. Computational head modeling of blunt impact events has shown that the linear acceleration response correlates well with increases in brain pressure [7]. Intracranial pressure, therefore, has been one of the major quantities investigated for correlation to blast induced TBI injury mechanisms [8–14].Copyright © 2013 by ASME

Split Hopkinson Pressure Bars are used to study dynamic material response in uniaxial compression, tension or torsion. Modifications of traditional test techniques have permitted the successful measurement of highly elastic soft biological tissue properties. Testing biological materials, specifically brain material, using the modified Split Hopkinson Pressure Bar method is effective in characterizing the tissue response at strain levels and strain rates that are greater than traditional tissue testing modalities. The high strain rate material properties are of particular interest for use in constitutive models that govern material response and injury predictions for computational models of the human body exposed to dynamic impact events. Since the use of viable brain material is critical, and the viability largely depends on post mortem interval, harvesting fresh, non-frozen brain tissue is critical. In this paper, we present the shear response of fresh human brain tissue under high rate loading. The investigated strain rates ranged from 25 to 248 strain/s. Specimen were prepared from various orientations and locations within the brain across two specimen. The average elastic modulus was 13.0 ± 10 kPa computed across all trials. The response was also characterized based on specimen, loading rate, and strain level to analyze contributing factors. This information is critical for targeting surrogate material properties and generating parameters for computational model constitutive equations.

Patients face two major difficulties following limb loss: phantom limb pain (PLP) in the residual limb and limited functionality in the prosthetic limb. Many studies have focused on decreasing PLP with mirror therapy, yet few have examined the same visual ameliorating effect with a virtual or prosthetic limb. Our study addresses the following key questions: (1) does PLP decrease through observation of a 3D limb in a virtual integration environment (VIE) and (2) can consistent surface electromyography (sEMG) signals from the VIE drive an advanced modular prosthetic limb (MPL)? Recorded signals from the residual limb were correlated to the desired motion of the phantom limb, and changes in PLP were scored during each VIE session. Preliminary results show an overall reduction in PLP and a trend toward improvement in signal-to-motion accuracy over time. These signals allowed MPL users to perform a wide range of hand motions.

Under-Body Blast (UBB) has emerged as the predominant threat to ground vehicles and Warfighter survivability. The force transference from the vehicle structure to the human body has resulted in serious injuries, with the thoracolumbar spine frequently damaged. Computational models of the human body are being generated to model human response and develop injury mitigation strategies. To effectively model the spine mechanics, the thoracolumbar ligaments, which serve varying roles in contributing to spine stability, must be characterized at relevant strains and strain rates. Adaptation of cervical spine testing methods has allowed for testing of isolated spinal ligaments including the Anterior Longitudinal Ligament (ALL), Posterior Longitudinal Ligament (PLL), and Ligamentum Flavum (LF). A high-rate servo-hydraulic test machine was used to execute a tensile test protocol for 24 complexes with loading rates ranging from 240 - 2800 mm/s and displacements of 25%, 50%, 75%, 100%, and 300% of the measured ligament length. Non-contact strain field measurements were recorded to produce a three dimensional strain field of the ligament surface. In order to provide the ligament data in a form which can be incorporated in the human computational models, analytical methods for modeling the ligament response are being investigated. Ultimately, this model will be optimized to be utilized in computational models of the lumbar spine.

Predicting spinal injury under high rates of vertical loading is of interest, but the success of computational models in modeling this type of loading scenario is highly dependent on the material models employed. Understanding the response of these biological materials at high strain rates is critical to accurately model mechanical response of tissue and predict injury. While data exists at lower strain rates, there is a lack of the high strain rate material data that are needed to develop constitutive models. The Split Hopkinson Pressure Bar (SHPB) has been used for many years to obtain properties of various materials at high strain rates. However, this apparatus has mainly been used for characterizing metals and ceramics and is difficult to apply to softer materials such as biological tissue. Recently, studies have shown that modifications to the traditional SHPB setup allow for the successful characterization of mechanical properties of biological materials at strain rates and peak strain values that exceed alternate soft tissue testing techniques. In this paper, the previously-reported modified SHPB technique is applied to characterize human intervertebral disc material under simple shear. The strain rates achieved range from 5 to 250 strain s-1. The results demonstrate the sensitivity to the disc composition and structure, with the nucleus pulposus and annulus fibrosus exhibiting different behavior under shear loading. Shear tangent moduli are approximated at varying strain levels from 5 to 20% strain. This data and technique facilitates determination of mechanical properties of intervertebral disc materials under shear loading, for eventual use in constitutive models.

Intraoperative patient registration may significantly affect the outcome of image-guided surgery (IGS). Image-based registration approaches have several advantages over the currently dominant point-based direct contact methods and are used in some industry solutions in image-guided radiation therapy with fixed X-ray gantries. However, technical challenges including geometric calibration and computational cost have precluded their use with mobile C-arms for IGS. We propose a 2D/3D registration framework for intraoperative patient registration using a conventional mobile X-ray imager combining fiducial-based C-arm tracking and graphics processing unit (GPU)-acceleration. The two-stage framework 1) acquires X-ray images and estimates relative pose between the images using a custom-made in-image fiducial, and 2) estimates the patient pose using intensity-based 2D/3D registration. Experimental validations using a publicly available gold standard dataset, a plastic bone phantom and cadaveric specimens have been conducted. The mean target registration error (mTRE) was 0.34 ± 0.04 mm (success rate: 100%, registration time: 14.2 s) for the phantom with two images 90° apart, and 0.99 ± 0.41 mm (81%, 16.3 s) for the cadaveric specimen with images 58.5° apart. The experimental results showed the feasibility of the proposed registration framework as a practical alternative for IGS routines.

Robotic telemanipulation can be used to project human capabilities and accomplish tasks that may not otherwise be practical or safe for direct human involvement. Examples include work in inhospitable environments, the completion of dangerous tasks where the risk to human life is to be avoided such as explosive disablement, remote task completion when personnel transportation is not practical or desired, and completion of tasks that may be accomplished more successfully by human operated robots than by humans alone. These tasks would benefit from highly dexterous robotic telemanipulation capabilities with intuitive control and haptic feedback for the operator. A novel haptic feedback system that incorporates kinesthetic, vibratory, and tactile feedback has been proposed and is in development for use with a highly dexterous robotic platform to achieve human capabilities projection. This paper presents a novel wearable fingertip tactile feedback device that integrates with a commercially available haptic feedback system to provide multi-modal feedback for teleoperation of an highly dexterous anthropomorphic robotic manipulator.

Osteotomies around hip acetabulum have become a routine surgical intervention in cases with constant pain without joint degeneration in adult dysplasia. However, it remains a challenge to plan and realign optimally the joint after osteotomy to reach best function and longevity in the clinical outcome. Tool tracking navigation systems have been available for many years but they have not become popular among surgeons because they extend operation time, require preoperative CT scan and, on the other hand, produce only marginal advantage in hands of an experienced surgeon. Real-time biomechanical assessment, based on computer analysis using preoperative CT-scanning, has become an interesting means to adjust the acetabular reorientation during surgery according to the patient’s individual structure and loading conditions. Further, real-time feedback allows the surgeon to foresee radiographic angles while performing fixation of the osteotomized fragment. Assessment of peak pressure and potential weight bearing area in real-time allows prospective and retrospective systematic biomechanical studies of patient outcomes. To conclude, a major development in navigation software is under way and we have so far seen a spectrum of new features like loading condition assessment in real time for osteotomies. This is, however, merely the start of a revolutionary change in operative planning in orthopaedics with the help of computer aided guiding and bioengineering.

The Revolutionizing Prosthetics 2009 program conducted by the Defense Advanced Research Projects Agency (DARPA) has resulted in a Virtual Integration Environment (VIE) that provides a common development platform for researchers and clinicians that design, model and build prosthetic limbs and then integrate and test them with patients. One clinical need that arose during the VIE development was a feature to easily create and model animations that represent patient activities of daily living (ADLs) and simultaneously capture real-time surface EMG activity from the residual limb corresponding to the ADLs. An application of this feature is being made by the Walter Reed Military Amputee Research Program (MARP) where they are utilizing the VIE to investigate methods of reducing upper extremity amputee phantom limb pain (PLP).

We have developed a hardware and software platform, the WiiEMG, for controlling the Wii™ video game console with surface electromyography (EMG). WiiEMG is intended to assist with training and performance assessment of myoelectric control of upper arm prostheses. For this application, a player wears skin surface electrodes over myoelectric control sites. A real-time signal analysis system acquires amplified EMG signals and classifies the activity patterns associated with different motions. In addition, the amplitude of this pattern is used as a velocity signal, which is differentiated to give acceleration. Finally, a scaled version of this acceleration value is input as an analog voltage into a modified Wiimote™ in place of the normal accelerometer, and the Wiimote communicates the data to the console. To evaluate the system's performance, six able-bodied subjects were used to test the WiiEMG by playing the game Wii Tennis™ using myoelectric control. Results are reported that show how users develop improved EMG control after only a few brief trials. Improved muscle and EMG control has the potential to benefit myoelectric limb use as well as motor skills rehabilitation.