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There are no manually propelled wheelchairs on the market that are mobile in both seated and standing positions. In response to this product gap, our group formerly designed a mobile manual standing wheelchair (MMSW) and gathered stakeholder feedback. The purpose of this study was to refine the MMSW based on feedback, including weight and width reduction, and evaluate its performance.The MMSW was subjected to ANSI/RESNA stability testing, and three male participants completed a subset of the wheelchair skills test, including a 100-m roll test in the MMSW (seated and standing) and in their ultralight wheelchair.The MMSW met ANSI/RESNA stability safety standards. During the 100-m roll test, participants reached speeds with the MMSW in both the standing and sitting postures similar or greater than those typical of moving in the home environment (1.11 m/s seated; 0.79 m/s standing). Mobility speeds in the MMSW in the standing position were about three times faster than average walking speeds in exoskeletons (0.26 m/s exoskeletons). With the addition of chain drive bracing to the MMSW, one user was able to reach speeds in the standing position similar to average neurotypical walking speeds indicating the possibility for wheelchair users to be able to move in pace with family and friends.All participants expressed interest in the MMSW to facilitate improved quality of life. Further work is needed to test the utility of the MMSW in home and community settings, and its potential effects on standing time and health outcomes.Implications for rehabilitationManual standing wheelchairs with standing mobility may increase functional utility and length of standing time for manual wheelchair usersIncreased standing time may lead to several health benefits for manual wheelchair users.

Objective To describe how using a supine arm cycle ergometer can safely reduce deconditioning experienced by patients with spinal cord injury or disorder (SCI/D) during their four to six weeks of complete bed rest after surgery to close a stage 4 pressure injury. Design This pilot project used a newly designed arm cycle ergometer (known as the M-PACE) that extends over the bed, allowing a patient to lie completely supine while exercising. Setting The M-PACE was designed and built at the Minneapolis Veterans Affairs Health Care System (MVAHCS) and pilot tested at the MVAHCS SCI/D Center. Participants Patients with SCI/D, recovering from flap surgery and deemed appropriate to use the arm cycle ergometer were enrolled in the pilot study (n = 47). Outcome measures A pre-post six-minute arm test (6MAT), a proxy for conditioning, was conducted on a subset (n = 15) of participants before and after the supine cycling exercise training program. Participants' rating of perceived exertion (RPE) scores were collected at cessation of each 6MAT. Participants gave feedback on their perception of using the M-PACE. Results/conclusions The 6MAT RPE was significantly reduced after training with the M-PACE while on bed rest (P = 0.003). Also, significantly more rotations were performed after completing the training program (P = 0.02). Further, study participants who accessed the M-PACE found using it helped offset the tedium of laying supine during flap surgery recovery. The differences in the 6MAT pre- to post measures indicate the M-PACE should be further studied for offsetting the normal deconditioning that occurs with extended bedrest.

There exist limited data to guide the development of methodologies for evaluating impact resilience of prosthetic ankle–foot systems, particularly regarding human-device interaction in ecologically valid scenarios. The purpose of this study was to biomechanically characterize foot–ground interactions during drop-landings among Service members with and without unilateral transtibial limb loss. Seven males with, and seven males without, unilateral transtibial limb loss completed six drop-landing conditions consisting of all combinations of three heights (20 cm, 40 cm, 60 cm) and two loads (with and without a 22.2 kg weighted vest). Peak ground reaction forces (GRF), vertical GRF loading rate and impulse, as well as ankle–foot, knee, and hip joint negative (absorption) powers and work were compared across groups (i.e., contralateral side and prosthetic side vs. uninjured controls) by height and load conditions. Loading occurred primarily in the vertical direction, and increased with increasing drop height and/or with added load. Vertical GRFs were overall ~ 15% smaller on the prosthetic side (vs. controls) with similar loading rates across limbs/groups. From the most challenging condition (i.e., 60 cm with 22 kg load), ankle–foot absorption energies on the prosthetic side were 64.6 (7.2) J; corresponding values were 187.4 (8.9) J for the contralateral limb and 161.2 (6.7) J among uninjured controls. Better understanding biomechanical responses to drop-landings in ecological scenarios will help inform future iterations of mechanical testing methodologies for evaluating impact resilience of prosthetic ankle–foot systems (enhancing prescription criteria and return-to-activity considerations) as well as identifying and mitigating risk factors for long-term secondary complications within the contralateral limb (e.g., joint degeneration).

Individuals with lower limb loss often wear a gel liner and enclosed socket for connecting to a terminal prosthetic device. Historically, a significant limitation to traditional liners and sockets is that they are thermal insulators, thereby trapping heat and moisture within, which can lead to numerous deleterious issues, including loss of suspension and residual limb skin problems, and, in turn, reductions in mobility, function, and overall quality of life. To mitigate these issues, new approaches are therefore needed to enhance the residual limb climate (e.g. breathability and air permeability), allowing the dispersal of heat and moisture from within the liner and socket.In this study, a multidisciplinary team sought to establish the feasibility of an innovative prosthetic liner-socket system, designed to improve residual limb climate by capitalizing on passive (i.e. nonpowered) ventilation to reduce temperature/moisture and improve socket comfort for persons with transtibial amputations. Focus group meetings, along with an iterative design approach, were implemented to establish innovative design and development concepts that led to a passively ventilated liner-socket system.Ex vivo design has supported the feasibility of developing a passively ventilated liner-socket. To build on these successes, future development and human subjects testing are needed to finalize a commercially viable system. Implementing a passively ventilated liner-socket system that improves residual limb health and comfort, without compromising function or mobility of the user, into standard clinical care may encourage a more active lifestyle and enhance the quality of life for individuals after lower limb loss.

During post-amputation recovery or rapid body mass change, residual limb volume can change quickly, requiring frequent adjustments or replacement of the socket to maintain fit. The aim of this pilot test was to evaluate the feasibility of using a three-dimensional-printed insert to extend the service life of a prosthetic socket after substantial residual limb volume loss.One research subject with a well-fitting transtibial prosthetic socket had an oversized socket fabricated to simulate substantial limb volume loss. The digital shapes of the oversized and well-fitting sockets were used to create a three-dimensional-printed insert to restore fit.Two-minute walk test distance decreased when using the oversized socket without the insert, but not when using the socket with the insert. Socket comfort score was 8+ under all conditions. These results suggest that three-dimensional-printed inserts may be an effective method of extending the service life of prosthetic sockets when rapid limb volume loss occurs.Three-dimensional (3D) printing gives prosthetists a new tool to manage large volume changes without refabricating entire sockets. Sockets can be fabricated in anticipation of volume gain/loss, using replaceable 3D-printed inserts to maintain fit and comfort.

Men and women with lower limb amputations struggle with managing the balance between prosthesis alignment and shoe heel rise. A novel prosthetic ankle-feet system is being developed to support a wider range of footwear options for men and women with lower limb amputations. Each rigid foot is customized to fit the footwear of choice and can be rapidly attached to (or released from) an ankle unit which remains attached to the prosthesis. The ankle unit has a mass of 318g and is small enough to fit in the design volume of a 22cm foot across a range of heel rises. The ankle uses elastomeric bumpers arranged in a wiper design to maximize space efficiency. Structural testing has shown that the 3D printed custom Nylon 12 feet withstood 4584N of forefoot loading without failure based on the ISO 10328 loading parameters, indicating suitable strength to support safe human use in the laboratory. The feet have a mass of 446g. Feedback from two women Veterans with lower limb amputations reinforced the importance of improving access to shoes with different heel rises. Future activities will include cyclic fatigue testing, additional weight reduction, and incorporating suggested design refinements.

A novel ankle-foot prosthesis with adjustable range-of-motion limits was developed to support implementation of gradual training protocols in the physical therapy of new amputees. Stakeholder interviews drove design requirements that guided the development. Our first prototype did not pass structural strength testing, but with minor revisions to some components, our second prototype was able to pass structural strength testing to the P6 load level (125kg user) of the ISO 10328 standard for prosthetic feet. The system is ready for laboratory testing with prosthesis users and clinicians to generate further insight for future design iterations.

Current manual standing wheelchairs are not mobile in the standing position. The addition of standing mobility may lead to improved health and function for the user and may increase utilization of standing wheelchairs. In this project, a chain drive system was fitted to a manual standing wheelchair, adding mobility in the standing position. The hand rims are accessible from both seated and standing positions. The prototype uses 16-inch drive wheels in front with casters in the rear. Additional anterior casters are elevated when seated for navigating obstacles and then descend when standing to create a six-wheeled base with extended anterior support. Stability testing shows the center of pressure remains within the base of support when leaning to the sides or front in both seated and standing positions. Four veterans with spinal cord injury provided feedback on the design and reported that mobility during standing was very important or extremely important to them. The veterans liked the perceived stability and mobility of the prototype and provided feedback for future refinements. For example, reducing the overall width (width from hand rim to hand rim) and weight could make this system more functional for users.

Previous work suggests that to restore postural stability for individuals with lower-limb amputation, ankle-foot prostheses should be designed with a flat effective rocker shape for standing. However, most commercially available ankle-foot prostheses are designed with a curved effective rocker shape for walking. To address the demands of both standing and walking, we designed a novel bimodal ankle-foot prosthesis that can accommodate both functional modes using a rigid foot plate and an ankle that can lock and unlock. The primary objective of this study was to determine if the bimodal ankle-foot system could improve various aspects of standing balance (static, dynamic, and functional) and mobility in a group of Veterans with lower-limb amputation (n = 18). Standing balance was assessed while subjects completed a series of tests on a NeuroCom Clinical Research System (NeuroCom, a Division of Natus, Clackamas, OR), including a Sensory Organization Test, a Limits of Stability Test, and a modified Motor Control Test. Few statistically significant differences were observed between the locked and unlocked ankle conditions while subjects completed these tests. However, in the absence of visual feedback, the locked bimodal ankle appeared to improve static balance in a group of experienced lower-limb prosthesis users whose PLUS-M mobility rating was higher than approximately 73% of the sample population used to develop the PLUS-M survey. Given the statistically significant increase in mean equilibrium scores between the unlocked and locked conditions (p = 0.004), future testing of this system should focus on new amputees and lower mobility users (e.g., Medicare Functional Classification Level K1 and K2 prosthesis users). Furthermore, commercial implementation of the bimodal ankle-foot system should include a robust control system that can automatically switch between modes based on the user’s activity.

Many Service members and Veterans with lower-limb amputations have the potential for high function and the desire to resume physically demanding occupations that require them to carry heavy loads (e.g., military service, firefighters, farmers, ranchers, construction workers). However, it is currently unclear which prosthetic feet best accommodate heavy load carriage while also providing good overall function and mobility during unweighted activities. The main objective of this study was to investigate the ability of currently available prosthetic ankle-foot systems to accommodate weighted walking by examining the mechanical characteristics (i.e., forefoot stiffness) and dynamic function (i.e., rocker radius, effective foot length ratio, and late-stance energy return) of prosthetic feet designed for high activity users. Load versus deflection curves were obtained for nine prosthetic ankle-foot systems using a servohydraulic test frame and load cell. Effective roll-over shape characteristics and late-stance energy return measures were then obtained using quantitative gait analysis for three users with unilateral, transtibial amputation. Results from mechanical and dynamic testing showed that although forefoot stiffness varied across the nine feet investigated in this study, changes measured in roll-over shape radius and effective foot length ratio were relatively small in response to weighted walking. At the same time, prosthetic feet with more compliant forefoot keel structures appeared to provide more late-stance energy return compared to feet with stiffer forefoot keel structures. These results suggest that prosthetic ankle-foot systems with compliant forefoot keel structures may better accommodate weighted walking by reducing the metabolic cost of physically demanding activities. However, to more fully understand the biomechanical and functional implications of these results, other factors, such as the residual-limb strength of the user and the overall stiffness profile of the prosthetic foot, should also be considered.

Most commercially available lower-limb prostheses are designed for walking, not for standing. The Minneapolis VA Health Care System has developed a bimodal prosthetic ankle-foot system with distinct modes for walking and standing [1]. With this device, a prosthesis user can select standing or walking mode in order to maximize standing stability or walking functionality, depending on the activity and context. Additionally, the prosthesis was designed to allow for an “automatic mode” to switch between standing and walking modes based on readings from an onboard Inertial Measurement Unit (IMU) without requiring user interaction to manually switch modes. A smartphone app was also developed to facilitate changing between walking, standing and automatic modes. The prosthesis described in [1] was used in a pilot study with 18 Veterans with lower-limb amputations to test static, dynamic, and functional postural stability. As part of the study, 17 Veterans were asked for qualitative feedback on the bimodal ankle-foot system (Table 1). The majority of participants (82%) expressed an interest in having an automatic mode. The participants also indicated that the automatic mode would need to reach walking mode on their first step and to lock the ankle quickly once the standing position was achieved. When asked about how they wanted to control the modes of the prosthesis, 82% wanted to use a physical switch and only 12% wanted to use a smartphone app. The results indicated that the following major design changes would be needed: 1) A fast and accurate automatic mode 2) A physical switch for mode changes This paper describes the use of machine learning algorithms to create an improved automatic mode and the use of stakeholder feedback to design a physical switch for the bimodal ankle-foot system.

In recent years, numerous prosthetic ankle-foot devices have been developed to address the demands of sloped walking for individuals with lower-limb amputation. The goal of this study was to compare the performance of a passive, hydraulic ankle-foot prosthesis to two related, non-hydraulic ankles based on their ability to minimize the socket reaction moments of individuals with transtibial amputation during a range of sloped walking tasks. After a two-week accommodation period, kinematic data were collected on seven subjects with a transtibial amputation walking on an instrumented treadmill set at various slopes. Overall, this study was unable to find significant differences in the torque at the distal end of the prosthetic socket between an ankle-foot prosthesis with a hydraulic range-of-motion and other related ankle-foot prosthesis designs (rigid ankle, multiaxial ankle) during the single-support phase of walking. In addition, socket comfort and perceived exertion were not significantly different for any of the ankle-foot prostheses tested in this study. These results suggest the need for further work to determine if more advanced designs (e.g., those with microprocessor control of hydraulic features, powered ankle-foot designs) can provide more biomimetic function to prosthesis users.

Previous studies have shown that the effective rocker shape of the physiologic ankle-foot system during standing and fore-aft swaying is much flatter than that used during walking, which indicates a more stable base of support for the standing/swaying activity. Previous work suggests that flat regions within the effective rocker shapes of prosthetic ankle-foot systems could provide enhanced stability for standing balance tasks. An experimental prosthetic foot was altered to provide three different flat region lengths within its effective rocker shape. It was hypothesized that longer flat regions of the effective rocker shape would lead to improved standing balance outcomes and reduced walking performance for unilateral transtibial prosthesis users. However, no significant changes were seen in the balance and mobility outcomes of 12 unilateral transtibial prosthesis users when using the three prosthetic foot conditions. Subjects in the study significantly preferred prosthetic feet with relatively low to moderate flat regions over those with long flat regions. All the subjects without loss of light touch or vibratory sensation selected the prosthetic foot with the shortest flat region. More work is needed to investigate the effects of prosthetic foot properties on balance and mobility of prosthesis users.

We study two-photon absorption (2PA) in two series of new free-base porphyrins with 4-(diphenylamino)stilbene or 4,4'-bis-(diphenylamino)stilbene (BDPAS) attached via pi-conjugating linkers at the porphyrin meso-position. We show that this new substitution modality increases the 2PA cross section in the Soret band region (excitation wavelength 750-900 nm) of the core porphyrin by nearly 2 orders of magnitude, from sigma(2) approximately 10 GM for the meso-phenyl-substituted analogue to sigma(2) approximately 10(3) GM for the ethynyl-linked BDPAS-porphyrin dyad. The 2PA properties are quantitatively described by considering two different and interfering 2PA quantum transition pathways. The first path involves virtual transition via intermediate one-photon resonance. The second path bypasses the intermediate resonance and occurs due to a large permanent dipole moment difference between the ground and the final electronic states. To our best knowledge, this is the first experimental observation of the combined effect of these two pathways on one particular two-photon transition, resulting in quantum-interference-modulated 2PA strength.

We demonstrate efficient generation of singlet oxygen upon two-photon excitation with 150-fs 780-nm laser pulses of a new porphyrin photosensitizer molecule whose two-photon absorption cross section has been considerably enhanced by chemical design.

INTRODUCTION When nondisabled persons walk on sloped or uneven surfaces, they make adjustments to the kinematics and kinetics of their gait patterns [1-4]. According to Hansen et al., the net result of kinematic changes can be viewed as a change in ankle alignment to account for the change in surface slope [1]. Furthermore, in nondisabled persons, the first step on a different surface is adapted to that surface [5-6]. But without direct neural control, persons with lower-limb amputations do not have the ability to adjust their prosthesis for every step. Failure to adapt to terrain can lead to increased peak loading in the socket, discomfort, and tissue damage on the residual limb [7] and may contribute to falls when an unexpected new surface is encountered. To realize a truly adaptive prosthesis, the alignment of the ankle must be set independently for each step based only on the mechanics of that step and the surface encountered. There are some nonadaptive lower-limb prostheses that are tolerant of terrain variance through the use of multiaxial deflecting elements or ranges of hydraulic damping placed in series with high stiffness foot plates or keels (e.g., Epirus and Echelon feet from Endolite; Miamisburg, Ohio). The physical stops at the end of the range of motion of these features still engage the high stiffness property at the same ankle angle regardless of surface slope, so the ankle torque-angle relationship for the high stiffness element remains at a single equilibrium point. Some microprocessor-controlled lower-limb prostheses are capable of changing alignment automatically, yet these systems often require incremental adjustments over several steps before adaptation is completed. Although these prostheses do adapt their alignment to surface slopes, they are not able to adjust for the first step on a new surface or for an uneven surface that is constantly changing slope. Some historical prosthetic foot-ankle systems were developed that provide first-step adaptation; however, these devices were not clinically viable. For example, Hans Mauch developed a passive mechanical prosthetic ankle that adapted to sloped surfaces [8]. The mechanism relied on gravity to hold a ball at the nadir of a track such that when the shank reached vertical the ball closed a port, essentially "locking" the ankle. This approach was well received by the test users; however, rotary hydraulic systems are difficult to seal properly and the device was discontinued because of hydraulic fluid leakage and the need for frequent maintenance. Hansen et al. have also developed two prototype foot-ankle systems that adapt on each step of walking based on nondisabled walking characteristics [9]. Williams et al. used a weight-activated knurled cam clutch to engage a high stiffness rubber bumper at foot flat [10]. The proof-of-concept prototype successfully demonstrated the plausibility of the concept, yet many improvements were needed, including refinement of the cam clutch mechanism and clutch engagement mechanism. Nickel et al. used a releasable wrap spring clutch mechanism to engage a high-stiffness rubber bumper at foot flat [11]. The prototype showed evidence of changing the equilibrium point in response to walking on sloped surfaces, but the clutch did not support sufficient torque. Our goal for the present work was to refine the design by Williams et al. and bring the concept closer to a clinically viable device. The refinements were aimed at (1) reducing engagement/disengagement noise by using a smooth cam surface instead of the knurled cam, (2) simplifying the engagement/disengagement mechanism by using a hinge instead of a telescoping slider, (3) redesigning the system to fit within a commercially available cosmetic foot shell, and (4) general design enhancements for structural strength, reduced weight, and reliable performance. METHODS Prototype Design The ankle-foot prototype of the present work (Figure 1) is designed to provide a step-specific equilibrium point, or set-point, setting the dorsiflexion-plantarflexion alignment (zero-torque angle) on each step based on the surface slope encountered. …

The human ankle-foot system conforms to a circular effective rocker shape for walking, but to a much flatter effective shape for standing and swaying. Many persons with lower limb amputations have impaired balance and reduced balance confidence, and may benefit from prostheses designed to provide flatter effective rocker shapes during standing and swaying tasks. This paper describes the development and testing of an ankle-foot prosthesis prototype that provides distinctly different mechanical properties for walking and standing/swaying. The prototype developed was a single-axis prosthetic foot with a lockable ankle for added stability during standing and swaying. The bimodal ankle-foot prosthesis prototype was tested on pseudoprostheses (walking boots with prosthetic feet beneath) for walking and standing/swaying loads, and was compared to an Otto Bock single-axis prosthetic foot and to able-bodied data collected in a previous study. The height-normalized radius of the effective rocker shape for walking with the bimodal ankle-foot prototype was equal to that found earlier for able-bodied persons (0.17); the standing and swaying effective shape had a lower height-normalized radius (0.70) compared with that previously found for able-bodied persons (1.11). The bimodal ankle-foot prosthesis prototype had a similar radius as the Otto Bock single-axis prosthetic foot for the effective rocker shape for walking (0.17 for both), but had a much larger radius for standing and swaying (0.70 for bimodal, 0.34 for single-axis). The results suggest that the bimodal ankle-foot prosthesis prototype provides two distinct modes, including a biomimetic effective rocker shape for walking and an inherently stable base for standing and swaying. The radius of the prototype's effective rocker shape for standing/swaying suggests that it may provide inherent mechanical stability to a prosthesis user, since the radius is larger than the typical body center of mass’s distance from the floor (between 50–60% of height). Future testing is warranted to determine if the bimodal ankle-foot prosthesis will increase balance and balance confidence in prosthesis users.

This article describes an inexpensive elastic head support for persons with amyotrophic lateral sclerosis (ALS) and neck muscle weakness and also presents a case series to examine its effectiveness. The device offers support to the head while the user is seated, standing, and walking, providing support for persons in various stages of ALS. The head support system was tested in seven male patients with ALS. Before and after the 2 wk trial, the subjects answered questions related to their communication efficacy, difficulty swallowing, level of neck discomfort, number of hours being upright before neck discomfort, comfort in social settings, and rating of perceived dyspnea. Subjects also answered specific questions related to the elastic head support after the 2 wk trial. The results suggested that the elastic head support is useful for some, but not all, patients.

The anatomical ankle is capable of providing adaptation to sloped surfaces, a function that is not available in most traditional lower limb prostheses. Commercial prostheses that are claimed to adapt to slopes are limited by high cost, delay in response, reduced stability, and loss of energy through damping. The purpose of the present work was to develop a prototypical prosthetic ankle unit that adapts to sloped surfaces and is sufficiently durable for short-term take-home trials. The prototype switches between low and high rotational impedances by means of a wrap spring clutch mechanism. The clutch is held in a disengaged position when unloaded and deflection of a compressible pylon under axial load rotates a control collar and engages the clutch. The prototype was subjected to 100,000 cycles of mechanical endurance testing based on ISO 10328 standards to determine the suitability for two-week take-home testing. Three persons with unilateral transtibial amputations were recruited to test the prototype in the laboratory, providing subjective feedback through a survey and participating in a motion analysis study to confirm the performance of the slope adaptation function. Translation of the ankle moment-angle curves for all subjects along the ankle angle axis demonstrated a change of the ankle alignment when subjects walked with the adaptable ankle on surfaces of different slopes. The ankle moment-angle curves had a lower slope than the subjects’ usual prostheses, and some subjects had distinct flat regions in the moment-angle curves when using the adaptable ankle. The arbors of the clutch demonstrated significant wear when tested to 100,000 cycles based on ISO 10328 standards, yet the adaptable ankle continued to hold testing loads. The alignment change observed for sloped surfaces suggests the prototype was providing slope adaptation. The flat regions on the ankle moment-angle curves suggest the clutch may have been slipping. Refinement of the clutch engagement mechanism and continued development to reduce the weight and size of the prototype is needed prior to take-home testing.