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For individuals with spinal cord injuries (SCIs) above the midthoracic level, a common complication is the partial or complete loss of trunk stability in the seated position. Functional neuromuscular stimulation (FNS) can restore seated posture and other motor functions after paralysis by applying small electrical currents to the peripheral motor nerves. In particular, the Networked Neuroprosthesis (NNP) is a fully implanted, modular FNS system that is also capable of capturing information from embedded accelerometers for measuring trunk tilt for feedback control of stimulation. The NNP modules containing the accelerometers are located in the body based on surgical constraints. As such, their exact orientations are generally unknown and cannot be easily assessed. In this study, a method for estimating trunk tilt that employed the Gram–Schmidt method to reorient acceleration signals to the anatomical axes of the body was developed and deployed in individuals with SCI using the implanted NNP system. An anatomically realistic model of a human trunk and five accelerometer sensors was developed to verify the accuracy of the reorientation algorithm. Correlation coefficients and root mean square errors (RMSEs) were calculated to compare target trunk tilt estimates and tilt estimates derived from simulated accelerometer signals under a variety of conditions. Simulated trunk tilt estimates with correlation coefficients above 0.92 and RMSEs below 5° were achieved. The algorithm was then applied to accelerometer signals from implanted sensors installed in three NNP recipients. Error analysis was performed by comparing the correlation coefficients and RMSEs derived from trunk tilt estimates calculated from implanted sensor signals to those calculated via motion capture data, which served as the gold standard. NNP-derived trunk tilt estimates exhibited correlation coefficients between 0.80 and 0.95 and RMSEs below 13° for both pitch and roll in most cases. These findings suggest that the algorithm is effective at estimating trunk tilt with the implanted sensors of the NNP system, which implies that the method may be appropriate for extracting feedback signals for control systems for seated stability with NNP technology for individuals who have reduced control of their trunk due to paralysis.

Feedback control of functional neuromuscular stimulation has the potential to improve daily function for individuals with spinal cord injuries (SCIs) by enhancing seated stability. Our fully implanted networked neuroprosthesis (NNP) can provide real-time feedback signals for controlling the trunk through accelerometers embedded in modules distributed throughout the trunk. Typically, inertial sensors are aligned with the relevant body segment. However, NNP implanted modules are placed according to surgical constraints and their precise locations and orientations are generally unknown. We have developed a method for calibrating multiple randomly oriented accelerometers and fusing their signals into a measure of trunk orientation. Six accelerometers were externally attached in random orientations to the trunks of six individuals with SCI. Calibration with an optical motion capture system resulted in RMSE below 5° and correlation coefficients above 0.97. Calibration with a handheld goniometer resulted in RMSE of 7° and correlation coefficients above 0.93. Our method can obtain trunk orientation from a network of sensors without a priori knowledge of their relationships to the body anatomical axes. The results of this study will be invaluable in the design of feedback control systems for stabilizing the trunk of individuals with SCI in combination with the NNP implanted technology.

Background Restoring or improving seated stability after spinal cord injury (SCI) can improve the ability to perform activities of daily living by providing a dynamic, yet stable, base for upper extremity motion. Seated stability can be obtained with activation of the otherwise paralyzed trunk and hip musculature with neural stimulation, which has been shown to extend upper limb reach and improve seated posture. Methods We implemented a proportional, integral, derivative (PID) controller to maintain upright seated posture by simultaneously modulating both forward flexion and lateral bending with functional neuromuscular stimulation. The controller was tested with a functional reaching task meant to require trunk movements and impart internal perturbations through rapid changes in inertia due to acquiring, moving, and replacing objects with one upper extremity. Five subjects with SCI at various injury levels who had received implanted stimulators targeting their trunk and hip muscles participated in the study. Each subject was asked to move a weighted jar radially from a center home station to one of three target stations. The task was performed with the controller active, inactive, or with a constant low level of neural stimulation. Trunk pitch (flexion) and roll (lateral bending) angles were measured with motion capture and plotted against each other to generate elliptical movement profiles for each task and condition. Postural sway was quantified by calculating the ellipse area. Additionally, the mean effective reach (distance between the shoulder and wrist) and the time required to return to an upright posture was determined during reaching movements. Results Postural sway was reduced by the controller in two of the subjects, and mean effective reach was increased in three subjects and decreased for one. Analysis of the major direction of motion showed return to upright movements were quickened by 0.17 to 0.32 s. A 15 to 25% improvement over low/no stimulation was observed for four subjects. Conclusion These results suggest that feedback control of neural stimulation is a viable way to maintain upright seated posture by facilitating trunk movements necessary to complete reaching tasks in individuals with SCI. Replication of these findings on a larger number of subjects would be necessary for generalization to the various segments of the SCI population.

Borno state in north-eastern Nigeria is the epicentre of the >10 years’ insurgency activities that have affected the region since 2009, resulting in the destruction of health facilities, killing of health workers, massive population displacement and lack of access to populations to provide health services. This article demonstrates how the involvement of community informants from insecure areas (CIIA) to conduct polio surveillance in security-challenged settlements of Borno state contributed to the expansion of polio surveillance reach beyond polio vaccination reach. In each of the 19 security compromised Local Government areas (LGAs) with community informants from insecure areas, Android phones enabled with Vaccination Tracking System (VTS) technology and Open Data Kit (ODK) mobile application were provided to capture geo-coordinates as evidence (geo evidence) for polio surveillance activity conducted. These geo evidence captured were uploaded and mapped to show insecure settlements reached with polio surveillance and those yet to be reached. A total of 3183 security compromised settlements were reached for polio surveillance between March 2018 and October 2019 with valid geo evidence, 542 of these security-compromised settlements had not been previously reached by any other intervention for polio surveillance or polio vaccination. The capturing of geo-coordinates as a proxy indicator of polio surveillance activity conducted by informants provided significant evidence of settlements reached for sustained polio surveillance even when a case of Acute Flaccid Paralysis (AFP) had not been reported from these settlements. Using the geo evidence captured by CIIA in insecure settlements, we have demonstrated the expansion of polio surveillance reach beyond polio vaccination reach in Borno state.

A two-part simulation process was developed to investigate the facilitation of vertical patient lifts with functional neuromuscular stimulation (FNS) in individuals with spinal cord injury (SCI). First, external lifting forces representing caregiver assistance were applied to a 3D musculoskeletal model representing the patient and optimized to enforce a specific lifting trajectory during a forward dynamic simulation. The process was repeated with and without the activation of the knee, hip, and trunk extensor muscles of the patient model to represent contractions of the paralyzed muscles generated via FNS. Secondly, the spinal compression experienced by a caregiver at the L5/S1 joint while generating these external lifting forces was estimated using a second musculoskeletal model representing the caregiver. Simulation without muscle activation predicted spinal compression in the caregiver model approximately 1.3 × the National Institute for Occupational Safety and Health (NIOSH) recommended “Action Limit.” Comparatively, simulations with two unique patterns of muscle activation both predicted caregiver spinal compressions below NIOSH recommendations. These simulation results support the hypothesis that FNS activation of a patient’s otherwise paralyzed muscles would lower the force output required of a caregiver during a dependent transfer, thus lowering the spinal compression and risk of injury experienced by a caregiver. Graphical abstract

Functional neuromuscular stimulation is a technique for restoring mobility impaired by spinal cord injury, including stepping. Typically, functional neuromuscular stimulation patterns are determined by manually tuning stimulation timing and charge applied to peripheral nerves by modulating constant current pulse amplitude, width, or frequency. Manual tuning is time consuming and suboptimal; we propose an in silico alternative relying on optimal control for developing temporal patterns of stimulation that can be implemented in real-life functional neuromuscular stimulation systems. The functional neuromuscular stimulation system user model includes only those muscles available for activation with an existing functional neuromuscular stimulation system; optimal control goals and constraints emphasize simplicity to allow solutions to differ from neurotypical neuromuscular behavior. Reduction of stimulation levels and upper extremity effort during stepping are prioritized in the optimal control problem. A single study participant with incomplete spinal cord injury walked with both model-optimized and manually tuned functional neuromuscular stimulation patterns to determine the relative benefits of each. The optimized pattern reduced charge delivery by an average of 58% (35%–80% for eight of nine muscles) and improved the comfortability of left side muscle contractions. Relative to the manually tuned pattern, the model-optimized stimulation decreased upper extremity effort by 10.5% during left swing. Participant-informed modeling combined with optimal control could lead to efficient, personalized stimulation patterns.

Background Functional neuromuscular stimulation, lower limb orthosis, powered lower limb exoskeleton, and hybrid neuroprosthesis (HNP) technologies can restore stepping in individuals with paraplegia due to spinal cord injury (SCI). However, a self-contained muscle-driven controllable exoskeleton approach based on an implanted neural stimulator to restore walking has not been previously demonstrated, which could potentially result in system use outside the laboratory and viable for long term use or clinical testing. In this work, we designed and evaluated an untethered muscle-driven controllable exoskeleton to restore stepping in three individuals with paralysis from SCI. Methods The self-contained HNP combined neural stimulation to activate the paralyzed muscles and generate joint torques for limb movements with a controllable lower limb exoskeleton to stabilize and support the user. An onboard controller processed exoskeleton sensor signals, determined appropriate exoskeletal constraints and stimulation commands for a finite state machine (FSM), and transmitted data over Bluetooth to an off-board computer for real-time monitoring and data recording. The FSM coordinated stimulation and exoskeletal constraints to enable functions, selected with a wireless finger switch user interface, for standing up, standing, stepping, or sitting down. In the stepping function, the FSM used a sensor-based gait event detector to determine transitions between gait phases of double stance, early swing, late swing, and weight acceptance. Results The HNP restored stepping in three individuals with motor complete paralysis due to SCI. The controller appropriately coordinated stimulation and exoskeletal constraints using the sensor-based FSM for subjects with different stimulation systems. The average range of motion at hip and knee joints during walking were 8.5°–20.8° and 14.0°–43.6°, respectively. Walking speeds varied from 0.03 to 0.06 m/s, and cadences from 10 to 20 steps/min. Conclusions A self-contained muscle-driven exoskeleton was a feasible intervention to restore stepping in individuals with paraplegia due to SCI. The untethered hybrid system was capable of adjusting to different individuals’ needs to appropriately coordinate exoskeletal constraints with muscle activation using a sensor-driven FSM for stepping. Further improvements for out-of-the-laboratory use should include implantation of plantar flexor muscles to improve walking speed and power assist as needed at the hips and knees to maintain walking as muscles fatigue.

Functional neuromuscular stimulation (FNS) can be used to restore seated trunk function in individuals paralyzed due to spinal cord injury (SCI). Musculoskeletal models allow for the design and tuning of controllers for use with FNS; however, these models often use aggregated estimates for parameters of the musculotendon elements, the most significant of which is maximum isometric force (MIF). Stimulated MIF for individuals with SCI is typically assumed to be approximately 50% of the values exhibited by able-bodied muscles, which itself varies between studies and individuals. A method for estimating subject-specific MIF during dynamic motions in individuals with SCI produced by electrical stimulation has been developed to test this assumption and obtained more accurate estimates for biomechanical analysis and controller design. A simple on-off controller was applied to individuals with SCI seated in the workspace of a motion capture system to record joint angles of three types of trunk motions: forward flexion, left and right lateral bending followed by returning, un-aided, to upright posture via neural stimulation delivered to activate the muscles of the hips and trunk. System identification was used with a musculoskeletal model to find the optimal MIF values that reproduced the experimentally observed motions. Experiments with five volunteers with SCI indicate that an MIF of the 50% able-bodied values commonly used is significantly lower than the identified estimates in 33 of 44 muscle groups tested. This suggests that the strengths of paralyzed muscles when stimulated with FNS have been underestimated in many situations and their true force outputs may be higher than the values suggested for use in simulation studies with musculoskeletal models. These findings indicate that subject-specific musculoskeletal models can more closely mimic the motions of subjects by using individualized estimates of MIF, which may allow the design and tuning of controllers while reducing the time spent with subjects in the loop.

This study explores the feasibility of a hybrid system of exoskeletal bracing and multichannel functional electrical stimulation (FES) to facilitate standing, walking, and stair climbing after spinal cord injury (SCI). The orthotic components consist of electromechanical joints that lock and unlock automatically to provide upright stability and free movement powered by FES. Preliminary results from a prototype device on nondisabled and SCI volunteers are presented. A novel variable coupling hip-reciprocating mechanism either acts as a standard reciprocating gait orthosis or allows each hip to independently lock or rotate freely. Rotary actuators at each hip are configured in a closed hydraulic circuit and regulated by a finite state postural controller based on real-time sensor information. The knee mechanism locks during stance to prevent collapse and unlocks during swing, while the ankle is constrained to move in the sagittal plane under FES-only control. The trunk is fixed in a rigid corset, and new ankle and trunk mechanisms are under development. Because the exoskeletal control mechanisms were built from off-the-shelf components, weight and cosmesis specifications for clinical use have not been met, although the power requirements are low enough to provide more than 4 hours of continuous operation with standard camcorder batteries.

Background From January to May 2019, large measles outbreaks affected Nigeria. Borno state was the most affected, recording 15,237 suspected cases with the state capital of Maiduguri having 1125 cases investigated and line-listed by March 2019. In Borno state, 22 of the 27 Local Government Areas (LGAs or Districts), including 37 internally displaced persons (IDPs) camps were affected . In response to the situation, an outbreak response immunization (ORI) campaign was conducted in the 13 most affected LGAs. In addition to conventional vaccination teams, special teams were deployed in security compromised areas, areas with migrants, and for nomadic and IDPs. Here we describe the outbreak and the ORI campaign. We also assess the measles-containing vaccine (MCV) coverage and vaccine effectiveness (VE) in order to quantify the population-level impact. Methods We reviewed the ORI activities, and conducted an analysis of the surveillance and the outbreak investigation reports. We assessed VE of MCV by applying the screening-method. Sensitivity analyses were also conducted to assess the effect of final classification of cases on the VE of MCV. The MCV coverage was assessed by a post-campaign coverage survey after completion of the ORI through a quantitative survey in the 12 LGAs that were accessible. Results Of the total 15,237 reported measles cases, 2002 cases were line-listed and investigated, and 737 were confirmed for measles by week 9 of 2019. Of the investigated cases 67.3% ( n  = 1348) were between 9 and 59 months of age. Among the 737 confirmed cases, only 9% ( n  = 64) stated being vaccinated with at least 1 dose of MCV. The overall VE for MCV was 98.4% (95%CI: 97.8–98.8). No significant differences were observed in the VE estimates of lab-confirmed and epi-linked cases when compared to the original estimates. The aggregated weighted vaccination coverage was 85.7% (95% CI: 79.6–90.1). Conclusion The experience in Borno demonstrates that adequate VE can be obtained in conflict-affected areas. In complex emergencies affected by measles outbreaks, health authorities may consider integration with other health strategies and the engagement of security personnel as part of the ORI activities.