The neuromuscular control for lower limb exoskeleton- a 50-year perspective.

Historically, impaired lower limb function has resulted in heavy health burden and large economic loss in society. Although experts from various fields have put large amounts of effort into overcoming this challenge, there is still not a single standard treatment that can completely restore the lost limb function. During the past half century, with the advancing understanding of human biomechanics and engineering technologies, exoskeletons have achieved certain degrees of success in assisting and rehabilitating patients with loss of limb function, and therefore has been spotlighted in both the medical and engineering fields. In this article, we review the development milestones of lower limb exoskeletons as well as the neuromuscular interactions between the device and wearer throughout the past 50 years. Fifty years ago, the lower-limb exoskeletons just started to be devised. We review several prototypes and present their designs in terms of structure, sensor and control systems. Subsequently, we introduce the development milestones of modern lower limb exoskeletons and discuss the pros and cons of these differentiated devices. In addition, we summarize current important neuromuscular control systems and sensors; and discuss current evidence demonstrating how the exoskeletons may affect neuromuscular control of wearers. In conclusion, based on our review, we point out the possible future direction of combining multiple current technologies to build lower limb exoskeletons that can serve multiple aims.

Additional Vitamin and Mineral Support for Patients with Severe Burns: A Nationwide Experience from a Catastrophic Color-Dust Explosion Event in Taiwan.

Major burn injuries, which encompass ≥20% of the total body surface area (TBSA), are the most severe form of trauma because of the stress response they provoke, which includes hypermetabolism, muscle wasting, and stress-induced diabetes. In 2015, a color-dust explosion disaster occurred in the Formosa Fun Coast of Taiwan and injured 499 people, who were transferred via a nationwide emergency delivery system. Some recommendations are currently available regarding vitamin and mineral support for wound healing and recovery in severe burns, but there is a lack of evidence to confirm the benefits. Thus, the current study aimed to investigate the effects of additional vitamin and mineral support for patients with severe burn injuries. Sixty-one hospitalized individuals with major burns (full thickness and ≥20% TBSA) were classified into the supplement (n = 30) and control (n = 31) groups, according to whether they received supplementation with additional vitamins, calcium, and magnesium. There were significant differences between the supplement and control groups in the incidence of wound infection (30.0% vs. 77.4%, p < 0.001), sepsis (13.3% vs. 41.9%, p = 0.021), and hospitalization days (51.80 vs. 76.81, p = 0.025). After adjustment, logistic regression analysis revealed that, compared to those in the control group, patients in the supplement group had a lower risk for wound infection (OR 0.11; 95% CI 0.03⁻0.43; p = 0.002) and sepsis (OR 0.09; 95% CI 0.01⁻0.61; p = 0.014). Supplementation of multiple vitamins, calcium, and magnesium reduced the risk of wound infection and sepsis, shortened the time of hospitalization, and can be considered for use in major burns.

A digital assessment system for evaluating kinetic tremor in essential tremor and Parkinson's disease.

BACKGROUND: Spiral drawing on papers is a common tremor evaluation tool for diagnosing patients with essential tremor (ET) or Parkinson's disease (PD). No standard drawing methods and parameters that use graphic tablets are yet available for objective evaluation. METHODS: This study established a tremor assessment system for tremor severity by using graphic tablets. Twelve patients with ET and twelve patients with PD were tested to establish system algorithms, and six additional patients were tested with the developed system to evaluate its performance. The patients also performed spiral drawing with three guiding paradigms on a graphic tablet: traced along a given spiral (S1), performed freehand drawing (S2), and traced along a guiding point (S3). Three parameters were calculated to quantify tremor severity: the means of radial difference per radian (|dr/dθ|), the means of radial difference per second (|dr/dt|), and the area under curve (AUC) of the frequency spectrum of the velocity. Each patient's drawing was also evaluated using a visual rating scale (VRS) by experienced physicians. The interrater reliability was examined to identify the most consistent test paradigm. RESULTS: The parameter |dr/dθ| and AUC correlated well with the VRS (R > 0.8) in S1, S2 and S3 tests. The S1 test presented the best interrater reliability (Weighted Kappa coefficient, k = 0.80) among three tests. The Weighted Kappa coefficients are 0.67 and 0.71 in S2 and S3 tests, respectively. CONCLUSIONS: We developed three different guiding paradigms for spiral drawing on a digital graphic tablet for clinical tests. Three parameters were calculated to represent the tremor severity in spiral drawing and used to quantify temporal and spatial characteristics of tremor, and provided good correlation with current clinical assessments. The test "traced along a given spiral" is recommended due to its good interrater reliability.

The difference in visuomotor feedback velocity control during spiral drawing between Parkinson's disease and essential tremor.

In a spiral task, the accuracy of the spiral trajectory, which is affected by tracing or tracking ability, differs between patients with Parkinson's disease (PD) and essential tremor (ET). However, not many studies have analyzed velocity differences between the groups during this task. This study aimed to examine differences between the groups related to this characteristic using a tablet. Fourteen PD, 12 ET, and 12 control group participants performed two tasks: tracing a given spiral (T1) and following a guiding point (T2). A digitized tablet was used to record movements and trajectory. Effects of direct visual feedback on intergroup and intragroup velocity were measured. Although PD patients had a significantly lower T1 velocity than the control group (p < 0.05), they could match the velocity of the guiding point (3.0 cm/s) in T2. There was no significant difference in the average T1 velocity between ET and the control groups (p = 0.26); however, the T2 velocity of ET patients was significantly higher than the control group (p < 0.05). They were also unable to adjust the velocity to match the guiding point, indicating that ET patients have a poorer ability to follow dynamic guidance. When both groups of patients have similar action tremor severity, their ability to follow dynamic guidance was still significantly different. Our study combined visual feedback with spiral drawing and demonstrated differences in the following-velocity distribution in PD and ET. This method may be used to distinguish the tremor presentation of both diseases, and thus, provide accurate diagnosis.

Local hemostatic matrix for endoscope-assisted removal of intracerebral hemorrhage is safe and effective.

BACKGROUND/PURPOSE: Minimally invasive endoscope-assisted (MIE) evacuation of spontaneous intracerebral hemorrhage (ICH) is simple and effective, but the limited working space may hinder meticulous hemostasis and might lead to rebleeding. Management of intraoperative hemorrhage is therefore a critical issue of this study. This study presents experience in the treatment of patients with various types of ICH by MIE evacuation followed by direct local injection of FloSeal Hemostatic Matrix (Baxter Healthcare Corp, Fremont, CA, USA) for hemostasis. METHODS: The retrospective nonrandomized clinical and radiology-based analysis enrolled 42 patients treated with MIE evacuation of ICH followed by direct local injection of FloSeal Hemostatic Matrix. Rebleeding, morbidity, and mortality were the primary endpoints. The percentage of hematoma evacuated was calculated from the pre- and postoperative brain computed tomography (CT) scans. Extended Glasgow Outcome Scale (GOSE) was evaluated at 6 months postoperatively. RESULTS: Forty-two ICH patients were included in this study, among these, 23 patients were putaminal hemorrhage, 16 were thalamic ICH, and the other three were subcortical type. Surgery-related mortality was 2.4%. The average percentage of hematoma evacuated was 80.8%, and the rebleeding rate was 4.8%. The mean operative time was 102.7 minutes and the average blood loss was 84.9 mL. The mean postoperative GOSE score was 4.55 at 6-months' follow-up. CONCLUSION: This study shows that local application of FloSeal Hemostatic Matrix is safe and effective for hemostasis during MIE evacuation of ICH. In our experience, this shortens the operation time, especially in cases with intraoperative bleeding. A large, prospective, randomized trial is needed to confirm the findings.

User experience of lower-limb orthosis.

If an assistive device is not acceptable to the user, it will not achieve efficacy and would be resource-wasting. This study employed in-depth interviews to understand what users' individual activities of daily living, problems of using orthoses, and considerations for selecting orthoses are. We conducted qualitative interviews with 35 lower-limb orthosis users, and semi-structured interviews were applied in this study. We analyzed the interview data from transcripts, through coding and concepts, to theories based on grounded theory. The results showed that problems of using orthoses are mostly related to activities of daily living of the user and user's expectation. Therefore, in order to enhance its efficacy and use intention, the design and prescribing process of orthoses need to address the problems in the light of activities of daily living and user education.

Development of method for quantifying essential tremor using a small optical device.

BACKGROUND: Clinical assessment scales are the most common means used by physicians to assess tremor severity. Some scientific tools that may be able to replace these scales to objectively assess the severity, such as accelerometers, digital tablets, electromyography (EMG) measurement devices, and motion capture cameras, are currently available. However, most of the operational modes of these tools are relatively complex or are only able to capture part of the clinical information; furthermore, using these tools is sometimes time consuming. Currently, there is no tool available for automatically quantifying tremor severity in clinical environments. NEW METHOD: We aimed to develop a rapid, objective, and quantitative system for measuring the severity of finger tremor using a small portable optical device (Leap Motion). RESULTS: A single test took 15s to conduct, and three algorithms were proposed to quantify the severity of finger tremor. The system was tested with four patients diagnosed with essential tremor. COMPARISON WITH EXISTING METHOD: The proposed algorithms were able to quantify different characteristics of tremor in clinical environments, and could be used as references for future clinical assessments. CONCLUSIONS: A portable, easy-to-use, small-sized, and noncontact device (Leap Motion) was used to clinically detect and record finger movement, and three algorithms were proposed to describe tremor amplitudes.

A study of Fitts' law on goal-directed aiming task with moving targets.

Most research based on Fitts' law define a log-linear relationship between temporal and spatial accuracy in goal-directed aiming tasks using stationary targets. Whether this relationship holds or not when the targets have varying velocities, and how the behavioral strategies and physical activities may change accordingly are of interest. The aim of this study was to investigate the relationship between temporal and spatial accuracy in goal-directed aiming tasks with moving targets. Participants were asked to aim at two target widths using a joystick. Results demonstrated that in a goal-directed aiming task there was a negative effect on performance when target velocity was increased or target width was decreased. Participants moved faster and then made more systematic errors in a high-velocity target condition. Results may be applicable to the complex perceptual-motor behavior of people who perform tasks using computers.

Effect of practice on stepping movements onto laterally compliant raised structures: age differences in healthy males.

OBJECTIVE: The aim of this study was to examine effects of practice and age on step-up movements onto raised structures. BACKGROUND: Falls from laterally compliant structures, such as stepladders, often cause injuries in elderly persons. Although age differences in step-up movements onto raised structures with unexpected structural compliance have been reported, practice effects of such movement control have not been investigated. METHOD: Movement behavior of 20 healthy adults (10 young and 10 older males) was measured while they stepped up onto a raised structure with no compliance (i.e., rigid) (C0), a small amount of mediolateral compliance (C1), or greater mediolateral compliance (C2). The conditions C0, C1, and C2 were presented in three sets of six fixed-order trials with step-up movements performed at a comfortable speed. Practice effects in step-up behavior were examined by comparing data within each trial block with the use of repeated-measures ANOVA. RESULTS: Practice significantly reduced the stepping duration (Ts) needed to complete the step-up movement (p < .001). With practice, older males reduced their lateral oscillations 26% to 40% for C1 and C2, whereas the corresponding results for young males lay between 8% and 17%, respectively. The age difference in Ts decreased across six consecutive trials but remained significant, especially on the structure with greater compliance. CONCLUSION: With practice, both young and elderly men adapted their stepping behavior to the presence of lateral structural compliance, but it is noteworthy from a fall-injury prevention perspective that the elderly men required more trials to do so. APPLICATION: Designers and users of raised structures, such as stepladders, should be aware of the age difference of people using such structures and should minimize the structure compliance when designing them.

Use of self-selected postures to regulate multi-joint stiffness during unconstrained tasks.

BACKGROUND: The human motor system is highly redundant, having more kinematic degrees of freedom than necessary to complete a given task. Understanding how kinematic redundancies are utilized in different tasks remains a fundamental question in motor control. One possibility is that they can be used to tune the mechanical properties of a limb to the specific requirements of a task. For example, many tasks such as tool usage compromise arm stability along specific directions. These tasks only can be completed if the nervous system adapts the mechanical properties of the arm such that the arm, coupled to the tool, remains stable. The purpose of this study was to determine if posture selection is a critical component of endpoint stiffness regulation during unconstrained tasks. METHODOLOGY/PRINCIPAL FINDINGS: Three-dimensional (3D) estimates of endpoint stiffness were used to quantify limb mechanics. Most previous studies examining endpoint stiffness adaptation were completed in 2D using constrained postures to maintain a non-redundant mapping between joint angles and hand location. Our hypothesis was that during unconstrained conditions, subjects would select arm postures that matched endpoint stiffness to the functional requirements of the task. The hypothesis was tested during endpoint tracking tasks in which subjects interacted with unstable haptic environments, simulated using a 3D robotic manipulator. We found that arm posture had a significant effect on endpoint tracking accuracy and that subjects selected postures that improved tracking performance. For environments in which arm posture had a large effect on tracking accuracy, the self-selected postures oriented the direction of maximal endpoint stiffness towards the direction of the unstable haptic environment. CONCLUSIONS/SIGNIFICANCE: These results demonstrate how changes in arm posture can have a dramatic effect on task performance and suggest that postural selection is a fundamental mechanism by which kinematic redundancies can be exploited to regulate arm stiffness in unconstrained tasks.

Stepping onto raised, laterally compliant structures: a biomechanical study of age and gender effects in healthy adults.

OBJECTIVE: To investigate the effects of gender and age on the kinematics and kinetics associated with stepping onto, and balancing on, a raised structure with lateral compliance. BACKGROUND: Falls from a stepladder tipping sideways are associated with considerable socioeconomic costs. METHOD: Ten young women (YF) and 10 young men (YM), aged 23 to 29 years, and 10 older men (OM) aged 66 to 75 years were asked to step up onto one of two raised structures with increasing lateral compliance (C1 and C2), presented in sets of six trials separated by up to 12 rigid (C0) structure trials. RESULTS: Structural compliance (C1 or C2) significantly affected step duration (p < .05) and lateral weight transfer velocity (p < .01). Significant age (p < .001) and gender (p < .05) differences were found in step duration and center of mass adjustments: With increasing structural compliance, participants required more time (YM: 15%; YF ranged from 33% to 45%; OM 35%-37%) to complete the step-up movement. CONCLUSION: Increasing age and structural compliance were both associated with larger and longer-lasting structural oscillations that increase the risk for a lateral fall. APPLICATION: Older adults, in particular, should not hurry their movements on raised structures. Actual or potential applications of this research include additional safety instructions for ladder users and considerations of structural compliance for designers and authors of national or international standards for raised structures.

Factors affecting stepladder stability during a lateral weight transfer: a study in healthy young adults.

A fall from a stepladder is often initiated by a loss of lateral stability. An inverted pendulum model of the human, validated by experiment, was used to determine the feasible range of whole-body center of mass (COM) states for which weight can be transferred laterally on a ladder tread without a ladder rail losing contact with the ground ("no lift-off" stability region). The results show that the size of the feasible no lift-off region was inversely proportional to the height of the tread above the ground, the distance of the stance foot from the ipsilateral rail, and lateral ground inclination angle. For given initial COM kinematics on a tread height equal to 40% human body height, a stance-foot location equal to one-eighth tread width and a 3.5 degrees ground inclination had approximately equivalent effects on the no lift-off region size. Ladder stability was three times more sensitive to tread height than to foot location. Laterally-exerted impulsive hand-tool forces should generally be limited to 8% body weight. These findings can lead to improved ladder designs and safety instructions for stepladder users.