Mechanism and design analysis of articulated ankle foot orthoses for drop-foot

Effects of 3D-printed ankle-foot orthoses on gait: a systematic review

This systematic review aimed to explore comprehensive evidence on the efficacy of the 3D-printed ankle-foot orthoses (AFOs) on gait parameters in individuals with neuromuscular and/or musculoskeletal ankle impairments. Electronic databases including PubMed, Scopus, Web of Science, Embase, ProQuest, Cochrane, and EBSCOhost were searched from inception to August 2023. Ten studies that had participants with ankle impairments, as a result of stroke, cerebral palsy, mechanical trauma, muscle weakness, or Charcot-Marie-Tooth disease, investigated the immediate effects of the 3D-printed AFOs on gait parameters were included. Methodological rigor was evaluated using the modified Downs & Black index. The gait parameters included lower extremity joint angles, moments, and work/power, plantar pressures, spatiotemporal measures, and patient satisfaction were improved with the 3D-printed AFOs when compared to the no-AFO (i.e. barefoot, or shoe-only) conditions. 3D-printed AFOs revealed similar functional efficacy as conventional AFOs. Notably, the level of patient satisfaction regarding fitting and comfort was higher with the 3D-printed AFOs. Although the study on the effects of the 3D-printed AFOs are limited, emerging evidence indicates their effectiveness in improving gait biomechanics and functions. To further confirm their effects, rigorous randomized control studies with larger sample sizes and longer follow-ups on the effects are warranted in the future.

The efficacy of the Novel Hybrid Passive Spring Damper Ankle Foot Orthosis regard to kinetic and kinematic parameters of patients with Multiple Sclerosis: An intervention study

Drop foot is a common consequence of Multiple Sclerosis (MS), which may be improved somewhat by an ankle-foot orthosis (AFO). This study aimed to examine the immediate effect of using the recently developed Novel Hybrid Passive Spring Damper AFO (the novel HPSDAFO) on the kinetic and kinematic parameters of patients with MS (PwMS) in the sagittal plane. Twelve PwMS who suffered a unilateral drop foot participated in this study and fitted with the novel HPSDAFO. They walked with the novel HPSDAFO on the affected side and shoe on the affected side at a self-selected speed. Walking by the novel HPSDAFO, the symmetry of all of the evaluated sagittal kinetic and kinematic parameters improved noticeably. The range of ankle plantarflexion and knee flexion increased significantly at the stance phase. Power generation increased at all three joints. The peak of ankle dorsiflexion at early stances and the first peak of knee extension moments increased significantly but decreased at the hip joint. Changes in sagittal ROM, moment, and power generation in the plane and the improved symmetry revealed a more normal walking by using the novel HPSDAFO on the affected limb of PwMS.

Enhancing walking performance in patients with peripheral arterial disease: An intervention with ankle-foot orthosis

Lower extremity peripheral artery disease (PAD) is a cardiovascular condition manifesting from narrowed or blocked arteries supplying the legs. Gait is impaired in patients with PAD. Recent evidence suggests that walking with carbon fiber ankle foot orthoses (AFOs) can improve patient mobility and delay claudication time. This study aimed to employ advanced biomechanical gait analysis to evaluate the impact of AFO intervention on gait performance among patients with PAD. Patients with claudication had hip, knee, and ankle joint kinetics and kinematics assessed using a cross-over intervention design. Participants walked over the force platforms with and without AFOs while kinematic data was recorded with motion analysis cameras. Kinetics and kinematics were combined to quantify torques and powers during the stance period of the gait cycle. The AFOs effectively reduced the excessive ankle plantar flexion and knee extension angles, bringing the patients' joint motions closer to those observed in healthy individuals. After 3 months of the AFO intervention, the hip range of motion decreased, likely due to changes occurring within the ankle chain. With the assistance of the AFOs, the biological power generation required from the ankle and hip during the push-off phase of walking decreased. Wearing AFOs resulted in increased knee flexor torque during the loading response phase of the gait. Based on this study, AFOs may allow patients with PAD to maintain or improve gait performance. More investigation is needed to fully understand and improve the potential benefits of ankle assistive devices.

Effects of ankle-foot orthoses on gait parameters in post-stroke patients with different Brunnstrom stages of the lower limb: a single-center crossover trial

BACKGROUND

Ankle-foot orthoses (AFO) can improve gait posture and walking ability in post-stroke patients. However, the effect of AFO on gait parameters in post-stroke patients according to the Brunnstrom stage of stroke recovery of the lower limbs remains unclear. The study aimed to investigate whether stroke patients with different Brunnstrom stages benefit from wearing AFO.

METHODS

Twenty-five post-stroke participants included 18 men (50 ± 13 years) and 7 women (60 ± 15 years). The patients were divided based on Brunnstrom stage III or IV of the lower limbs. All patients underwent the gait and timed up and go (TUG) test using a gait analysis system while walking barefoot or with an AFO. The spatiotemporal and asymmetric parameters were analyzed.

RESULTS

All 25 patients completed the study. Significant differences were observed between barefoot and AFO use in TUG time (P < 0.001) but not walking velocity (P > 0.05). The main effect of the swing time ratio was significant in both groups (P < 0.05); however, the main effects of stride length, stance time, and gait asymmetry ratio were nonsignificant (P > 0.05). For barefoot versus AFO, the main effects of stride length (P < 0.05) and swing time (P < 0.01) ratios were significant, whereas those of stance time and gait asymmetry ratio were nonsignificant (P > 0.05).

CONCLUSIONS

Post-stroke patients with lower Brunnstrom stages benefitted more from AFO, particularly in gait asymmetry.

Adaptive state restricted barrier Lyapunov-based control of a Stewart platform used as ankle-controlled mobilizer

In this research project, a closed-chain robotic active ankle orthosis with six degrees of freedom is designed, constructed, numerically valued, instrumented, and experimentally validated. The mechanical arrangement to implement the orthosis corresponds to a six-legged Stewart platform. An adaptive gain control strategy with state constraints based on a state-dependent gains control (that behaves as a diverging function as the states approach the state restrictions) operates the device's motion. The convergence to an invariant positive set centered at the origin of the tracking error space is validated using the stability analysis based on the second method of Lyapunov, with the implementation of a state barrier Lyapunov-like function. The ultimate boundedness of the tracking error is proven with an endorsed gains adjustment method leading to a reachable minimum size of the ultimate bound. Hence, the impact of the state constraints and the formal reason for applying the controller on the suggested orthosis are all established. The orthosis is also controlled using a conventional state feedback strategy to assess the tracking error for an external disturbance and contrast its performance with the proposed control approach. The technology is tested on a few carefully chosen volunteers, successfully limiting the range of motion within a pre-defined region based on the scope of movement reported by patients with ankle illnesses discovered in the literature. Based on a unique mechatronic device, the created system offers a fresh approach to treating this class of impairments.

NSF DARE-transforming modeling in neurorehabilitation: a patient-in-the-loop framework

In 2023, the National Science Foundation (NSF) and the National Institute of Health (NIH) brought together engineers, scientists, and clinicians by sponsoring a conference on computational modelling in neurorehabiilitation. To facilitate multidisciplinary collaborations and improve patient care, in this perspective piece we identify where and how computational modelling can support neurorehabilitation. To address the where, we developed a patient-in-the-loop framework that uses multiple and/or continual measurements to update diagnostic and treatment model parameters, treatment type, and treatment prescription, with the goal of maximizing clinically-relevant functional outcomes. This patient-in-the-loop framework has several key features: (i) it includes diagnostic and treatment models, (ii) it is clinically-grounded with the International Classification of Functioning, Disability and Health (ICF) and patient involvement, (iii) it uses multiple or continual data measurements over time, and (iv) it is applicable to a range of neurological and neurodevelopmental conditions. To address the how, we identify state-of-the-art and highlight promising avenues of future research across the realms of sensorimotor adaptation, neuroplasticity, musculoskeletal, and sensory & pain computational modelling. We also discuss both the importance of and how to perform model validation, as well as challenges to overcome when implementing computational models within a clinical setting. The patient-in-the-loop approach offers a unifying framework to guide multidisciplinary collaboration between computational and clinical stakeholders in the field of neurorehabilitation.

Effects of ankle-foot orthoses on step activities in the community: a systematic review

PURPOSE

To determine the effects of ankle-foot orthoses (AFO) on step-based physical activities in individuals with neurological, orthopaedic, or cardiovascular disorders.

METHODS

Electronic searches of databases such as Scopus, PubMed, Web of Science, Embase, ProQuest, Cochrane Library, and EBSCO were conducted. Two evaluators independently searched with keywords focusing on step-based physical activities, and either articulated or non-articulated AFO. Study quality was assessed using a modified Downs and Black quality scale.

RESULTS

Eleven studies that met the inclusion criteria were selected, including four being classified as good, four as fair, and three as poor in quality. The majority of these trials found no significant effects of AFO on step activities. Only a few studies reported improvements in step counts and active times in step activity with a limited to moderate level of evidence. Subjective evaluations such as user satisfaction, and physical functionality during step activity, on the other hand, showed substantial changes with the use of AFO interventions, although there was no evidence of improvement in the quality of life.

CONCLUSIONS

Although the AFO did not seem to have a substantial effect on step activity, it appeared to play a vital role in improving the patient satisfaction level of step activity.IMPLICATIONS FOR REHABILITATIONAnkle-foot orthoses (AFO) may not significantly affect the step activity of individuals with impaired ankle-foot complex.AFO may enhance patient-reported satisfaction, physical functioning, participation, and fatigue level during step activity.The patient's perception that the AFO is beneficial is in contrast to objective data showing no significant increase in real-world activity.

Design and characterization of a variable-stiffness ankle-foot orthosis

BACKGROUND

Ankle-foot orthoses (AFOs) are a type of assistive device that can improve the walking ability of individuals with neurological disorders. Adjusting stiffness is a common way to customize settings according to individuals' impairment.

OBJECTIVE

This study aims to design a variable-stiffness AFO by stiffness module and characterize the AFO stiffness range to provide subject-specific settings for the users.

METHODS

We modeled AFO using bending beams with varying fulcrum positions to adjust the stiffness. To characterize the stiffness range and profile, we used the superposition method to generate the theoretical model to analyze the AFO numerically. The intrinsic deformation of the bending beam in the AFO is considered a combination of 2 bending deformations to replicate actual bending conditions. The corresponding experiments in different fulcrum positions were performed to compare with and optimize the theoretical model. The curve fitting method was applied to tune the theoretical model by adding a fulcrum position-related coefficient.

RESULTS

The AFO stiffness increased as the fulcrum moved to the proximal position. The maximum stiffness obtained was 1.77 Nm/° at a 6-cm fulcrum position, and the minimum stiffness was 0.82 Nm/° at a 0.5-cm fulcrum position with a 0.43-cm thick fiberglass beam. The corresponding theoretical model had maximum and minimum stiffness of 1.71 and 0.80 Nm/°, respectively. The theoretical model had a 4.08% difference compared with experimental values.

CONCLUSIONS

The stiffness module can provide adjustable stiffness with the fulcrum position and different kinds of fiberglass bars, especially the thickness and material of the beam. The theoretical model with different fulcrum positions can be used to profile the real-time stiffness of the AFO in a dynamic motion and to determine the appropriate dimensions of the bending beam.

Sciatic and tibial neuropathies

The sciatic nerve is the body's largest peripheral nerve. Along with their two terminal divisions (tibial and fibular), their anatomic location makes them particularly vulnerable to trauma and iatrogenic injuries. A thorough understanding of the functional anatomy is required to adequately localize lesions in this lengthy neural pathway. Proximal disorders of the nerve can be challenging to precisely localize among a range of possibilities including lumbosacral pathology, radiculopathy, or piriformis syndrome. A correct diagnosis is based upon a thorough history and physical examination, which will then appropriately direct adjunctive investigations such as imaging and electrodiagnostic testing. Disorders of the sciatic nerve and its terminal branches are disabling for patients, and expert assessment by rehabilitation professionals is important in limiting their impact. Applying techniques established in the upper extremity, surgical reconstruction of lower extremity nerve dysfunction is rapidly improving and evolving. These new techniques, such as nerve transfers, require electrodiagnostic assessment of both the injured nerve(s) as well as healthy, potential donor nerves as part of a complete neurophysiological examination.

Design and Evaluation of Hybrid Passive Spring Damper Ankle Foot Orthosis for Gait Performance in Drop Foot Patients: A Feasibility Study

Passive and hybrid passive Ankle foot orthoses (AFOs) are the prevalent prescription in drop foot patients to prevent toe dragging during the swing phase. While, these AFOs have some limitations like inability to overcome foot slap, limitation in forward propulsion and inappropriate power generate at the push off. The aim of this study was to design a novel spring damper and evaluate the immediate effects of this AFO on improving the ankle kinetic and kinematic in drop foot patients. This AFO was generated from carbon composite frame and foot section with posterior hinge and spring damper actuator that controlled plantar flexion resistance at the early stance, freely dorsi flexion movement with the ability to store energy during mid-stance movement as well as restore this energy at the pre swing phase. This AFO was assessed on ten drop foot patients who used Posterior Leaf Spring AFO conditions and walked at their self-comfortable walking speed. Then the ankle kinetic and kinematic data in two conditions of with PLS (Posterior Leaf Spring) AFO, and novel spring damper AFO were assessed. Results showed a significant improve in the immediate effect of the kinetic and kinematic parameters. In conclusion, spring damper AFO improved all ankle angles in entire gait cycle as well as the ankle moments and power. Therefore, this AFO should be consider as a selective AFO in drop foot patients.

Advances on mechanical designs for assistive ankle-foot orthoses

Assistive ankle-foot orthoses (AAFOs) are powerful solutions to assist or rehabilitate gait on humans. Existing AAFO technologies include passive, quasi-passive, and active principles to provide assistance to the users, and their mechanical configuration and control depend on the eventual support they aim for within the gait pattern. In this research we analyze the state-of-the-art of AAFO and classify the different approaches into clusters, describing their basis and working principles. Additionally, we reviewed the purpose and experimental validation of the devices, providing the reader with a better view of the technology readiness level. Finally, the reviewed designs, limitations, and future steps in the field are summarized and discussed.

Comparison between a novel helical and a posterior ankle-foot orthosis on gait in people with unilateral foot drop: a randomised crossover trial

BACKGROUND

Neuromuscular disease and peripheral neuropathy may cause drop foot with or without evertor weakness. We developed a helical-shaped, non-articulated ankle-foot orthosis (AFO) to provide medial-lateral stability while allowing mobility, to improve gait capacity. Our aim was to evaluate the effect of the helical AFO (hAFO) on functional gait capacity (6-min walk test) in people with peripheral neuropathy or neuromuscular disease (NMD) causing unilateral drop foot and compare with a posterior leaf spring AFO (plsAFO). Secondary aims were to compare functional mobility, 3D kinematic and kinetic gait variables and satisfaction between the AFOs.

METHODS

Single centre, randomised crossover trial from January to July 2017 in 20 individuals (14 with peripheral neuropathy and 6 with NMD, 12 females, mean age 55.6 years, SD 15.3); 10 wore the hAFO for the first week and 10 wore the plsAFO before switching for the second week. The 6-min walk test (6MWT), Timed Up and Go (TUG) test and 3D gait analysis were evaluated with the hAFO, the plsAFO and shoes only (noAFO) at inclusion and 1 week after wearing each orthosis. Satisfaction was evaluated with the Quebec user evaluation of satisfaction with assistive technology (QUEST).

RESULTS

Median [interquartile range] 6MWT distance was greater with the hAFO (444 m [79]) than the plsAFO (389 m [135], P < 0.001, Hedge's g = 0.6) and noAFO (337 m [91], P < 0.001, g = 0.88). TUG time was shorter with the hAFO (8.1 s [2.8]) than the plsAFO (9.5 s [2.6], P < 0.001, g = - 0.5) and noAFO (10.0 s [2.6]), P < 0.001, g = - 0.6). The plsAFO limited plantarflexion during the loading response (plsAFO - 7.5 deg [6.0] vs. noAFO -13.0 deg [10.0], P = 0.0007, g = - 1.0) but the hAFO did not (- 11.0 deg [5.1] vs. noAFO, P = 0.05, g = - 0.5). Quasi-stiffness was lower for the hAFO than plsAFO (P = 0.009, g = - 0.7). The dimensionless eversion moment was higher (though not significantly) with the hAFO than noAFO. Neither orthosis reduced ankle power (P = 0.34). Median total QUEST score was higher for the hAFO (4.7 [0.7]) than the plsAFO (3.6 [0.8]) (P < 0.001, g = 1.9).

CONCLUSIONS

The helical orthosis significantly and considerably improved functional gait performance, did not limit ankle mobility, increased lateral stability, though not significantly, and was associated with greater patient satisfaction than the posterior leaf spring orthosis. Trial registration The trial began before registration was mandatory.

Perspectives on ankle-foot technology for improving gait performance of children with Cerebral Palsy in daily-life: requirements, needs and wishes

BACKGROUND

Ankle-foot orthoses (AFOs) are extensively used as a primary management method to assist ambulation of children with Cerebral Palsy (CP). However, there are certain barriers that hinder their prescription as well as their use as a mobility device in all kinds of daily-life activities. This exploratory research attempts to further understand the existing limitations of current AFOs to promote a better personalization of new design solutions.

METHODS

Stakeholders' (professionals in CP and end-users with CP) perspectives on AFO technology were collected by two online surveys. Respondents evaluated the limitations of current assistive solutions and assessment methods, provided their expectations for a new AFO design, and analyzed the importance of different design features and metrics to enrich the gait performance of these patients in daily-life. Quantitative responses were rated and compared with respect to their perceived importance. Qualitative responses were classified into themes by using content analysis.

RESULTS

130 survey responses from ten countries were analyzed, 94 from professionals and 36 from end-users with CP. The most highly rated design features by both stakeholder groups were the comfort and the ease of putting on and taking off the assistive device. In general, professionals preferred new features to enrich the independence of the patient by improving gait at functional levels. End-users also considered their social acceptance and participation. Health care professionals reported a lack of confidence concerning decision-making about AFO prescription. To some degree, this may be due to the reported inconsistent understanding of the type of assistance required for each pathological gait. Thus, they indicated that more information about patients' day-to-day walking performance would be beneficial to assess patients' capabilities.

CONCLUSION

This study emphasizes the importance of developing new approaches to assess and treat CP gait in daily-life situations. The stakeholders' needs and criteria reported here may serve as insights for the design of future assistive devices and for the follow-up monitoring of these patients.

Recent advances in wearable actuated ankle-foot orthoses: Medical effects, design, and control

This paper presents a survey on recent advances of wearable actuated ankle-foot orthoses (AAFOs). First of all, their medical functions are investigated. From the short-term aspect, they lead to rectification of pathological gaits, reduction of metabolic cost, and improvement of gait performance. After AAFO-based walking training with sufficient time, free walking performance can be enhanced. Then, key design factors are studied. First, primary design parameters are investigated. Second, common actuators are analysed. Third, human-robot interaction (HRI), ergonomics, safety, and application places, are considered. In the following section, control technologies are reviewed from the aspects of rehabilitation stages, gait feature quantities, and controller characteristics. Finally, existing problems are discussed; development trends are prospected.

Effects of powered ankle-foot orthoses mass distribution on lower limb muscle forces-a simulation study

This simulation study aimed to explore the effects of mass and mass distribution of powered ankle-foot orthoses, on net joint moments and individual muscle forces throughout the lower limb. Using OpenSim inverse kinematics, dynamics, and static optimization tools, the gait cycles of ten subjects were analyzed. The biomechanical models of these subjects were appended with ideal powered ankle-foot orthoses of different masses and actuator positions, as to determine the effect that these design factors had on the subject's kinetics during normal walking. It was found that when the mass of the device was distributed more distally and posteriorly on the leg, both the net joint moments and overall lower limb muscle forces were more negatively impacted. However, individual muscle forces were found to have varying results which were attributed to the flow-on effect of the orthosis, the antagonistic pairing of muscles, and how the activity of individual muscles affect each other. It was found that mass and mass distribution of powered ankle-foot orthoses could be optimized as to more accurately mimic natural kinetics, reducing net joint moments and overall muscle forces of the lower limb, and must consider individual muscles as to reduce potentially detrimental muscle fatigue or muscular disuse. OpenSim modelling method to explore the effect of mass and mass distribution on muscle forces and joint moments, showing potential mass positioning and the effects of these positions, mass, and actuation on the muscle force integral.

Effect of ankle-foot orthoses on functional outcome measurements in individuals with stroke: a systematic review and meta-analysis

PURPOSE

To determine and compare the effect of ankle-foot orthosis (AFOs) types on functional outcome measurements in individuals with (sub)acute or chronic stroke impairments.

METHODS

PubMed, Web of Knowledge, Embase, Scopus, ProQuest, and Cochrane were searched from inception until September 2020. Methodological quality assessment of 30 studies was conducted based on the Downs and Black checklist. Functional indices were pooled according to their standardized mean difference (SMD) and 95% confidence intervals (CI) in a random-effect model. A narrative analysis was performed where data pooling was not feasible.

RESULTS

Overall pooled results indicated improvements in favor of AFOs versus without for the Berg Balance Scale (SMD: 0.54, CI: 0.19-0.88), timed-up and go test (SMD: -0.45, CI: -0.67 to -0.24), Functional Ambulatory Categories (SMD: 1.72, CI: 1.25-2.19), 6-Minute Walking Test (SMD: 0.91, CI: 0.53-1.28), Timed Up-Stairs (SMD: -0.35, CI: -0.64 to 0.05), and Motricity Index (SMD: 0.65, CI: 0.38-0.92). Heterogeneity was non-significant for all outcomes (I² < 50%, p > 0.05) except the Berg Balance Scale and Functional Ambulatory Categories. Additionally, there was not sufficient evidence to determine the effectiveness of specific orthotic designs over others.

CONCLUSIONS

An AFO can improve ambulatory function in stroke survivors. Future studies should explore the long-term effects of rehabilitation using AFOs and compare differences in orthotic designs.IMPLICATIONS FOR REHABILITATIONAn AFO can improve functional performance and ambulation in survivors of strokes.Wearing an AFO in rehabilitation care during the subacute phase post stroke may have beneficial effects on functional outcomes measured.There was no evidence as to the effectiveness of specific AFO designs over others.

Robotic ankle control can provide appropriate assistance throughout the gait cycle in healthy adults

Ankle foot orthoses are mainly applied to provide stability in the stance phase and adequate foot clearance in the swing phase; however, they do not sufficiently assist during the entire gait cycle. On the other hand, robotic-controlled orthoses can provide mechanical assistance throughout the phases of the gait cycle. This study investigated the effect of ankle control throughout the gait cycle using an ankle joint walking assistive device under five different robotic assistance conditions: uncontrolled, dorsiflexion, and plantar flexion controlled at high and low speeds in the initial loading phase. Compared with the no-control condition, the plantar flexion condition enhanced knee extension and delayed the timing of ankle dorsiflexion in the stance phase; however, the opposite effect occurred under the dorsiflexion condition. Significant differences in the trailing limb angle and minimum toe clearance were also observed, although the same assistance was applied from the mid-stance phase to the initial swing phase. Ankle assistance in the initial loading phase affected the knee extension and ankle dorsiflexion angle during the stance phase. The smooth weight shift obtained might have a positive effect on lifting the limb during the swing phase. Robotic ankle control may provide appropriate assistance throughout the gait cycle according to individual gait ability.

Research and Development of Ankle-Foot Orthoses: A Review

The ankle joint is one of the important joints of the human body to maintain the ability to walk. Diseases such as stroke and ankle osteoarthritis could weaken the body's ability to control joints, causing people's gait to be out of balance. Ankle-foot orthoses can assist users with neuro/muscular or ankle injuries to restore their natural gait. Currently, passive ankle-foot orthoses are mostly designed to fix the ankle joint and provide support for walking. With the development of materials, sensing, and control science, semi-active orthoses that release mechanical energy to assist walking when needed and can store the energy generated by body movement in elastic units, as well as active ankle-foot orthoses that use external energy to transmit enhanced torque to the ankle, have received increasing attention. This article reviews the development process of ankle-foot orthoses and proposes that the integration of new ankle-foot orthoses with rehabilitation technologies such as monitoring or myoelectric stimulation will play an important role in reducing the walking energy consumption of patients in the study of human-in-the-loop models and promoting neuro/muscular rehabilitation.

Development and Evaluation of Dorsiflexion Support Unit Using Elastomer Embedded Flexible Joint

In our previous study, we developed a walking support shoe with an elastomer-embedded flexible joint (EEFJ) to assist the function of tibialis anterior (TA) in initial stances (IC) and swing phases (SW). However, its usability and supporting effect have not been sufficiently evaluated. Therefore, in this study, we developed a dorsiflexion support unit (DSU) using the EEFJs with consideration on the usability for frail persons. Their needs were investigated in hearings at community centers. With reference to their comments, we proposed a three-phased scenario in which pre- / post-activities were considered as important factors of its product design of the DSU. We designed the DSU for better usability in the pre- / post-activities. Its basic function and mechanical properties were also investigated in experiments. According to the mechanical tests, the supporting torque was around 10% of the activation of TA in IC. In addition, the results of gait tests show reductions of ankle rotations by 17% and 11% in IC and SW, respectively, without significant increases of TA activations.

Evaluation and Management of Adult Footdrop

Footdrop is a common musculoskeletal condition defined by weakness in ankle joint dorsiflexion. Although the etiology varies, footdrop is characterized by specific clinical and gait abnormalities used by the patient to overcome the loss of active ankle dorsiflexion. The condition is often associated with deformity because soft-tissue structures may become contracted if not addressed. Patients may require the use of special braces or need surgical treatment to address the notable level of physical dysfunction. Surgical treatment involving deformity correction to recreate a plantigrade foot along with tendon transfers has been used with notable success to restore a near-normal gait. However, limitations and postoperative dorsiflexion weakness have prompted investigation in nerve transfer as a possible alternative surgical treatment.

Therapeutic effect of gait training with two types of ankle-foot orthoses on the gait of the stroke patients in the recovery phase

Objectives

This study aimed to demonstrate the therapeutic effect of gait training using ankle-foot orthoses (AFOs) on the gait of stroke patients when not wearing AFOs with two different types of AFO, an AFO with an oil damper (AFO-OD) that resists plantarflexion and an AFO with a plantarflexion stop (AFO-PS), and to display the possible differences between the AFO types.

Patients and methods

Forty-two patients (38 males, 4 males, mean age: 59.7±10.9; range, 38 to 81 years) with subacute stroke were randomized to either an AFO-PS or an AFO-OD group. Participants were given gait training in a two-week period by physiotherapists wearing their allocated AFO. Nineteen patients were assigned to the AFO-PS group and 20 to the AFO-OD group. Patients' gait without an AFO before gait training and then after two weeks of training wearing allocated AFOs was recorded through a three-dimensional movement capture system.

Results

A therapeutic effect through two weeks of continuous use of AFOs and gait training was found in both AFO groups (main effect of time) in the spatiotemporal factors, ankle joint moments, ankle power generation, shank-to-vertical angle, and center of gravity velocity throughout the stance phase, pre-swing knee angular velocity, and hip flexion moment in pre-swing. The results did not show a large interaction between two AFOs group.

Conclusion

These findings reveal that both AFOs had significant therapeutic effects on stroke gait. There was no significant difference between the two AFO groups. Further studies with a control group representing the effects of gait training without wearing an AFO are needed.

Investigating the effects of conventional thermoplastic ankle-foot and the neoprene ankle-foot orthoses on the kinetics and kinematics of gait in people with foot drop following traumatic injury of the peroneal nerve: A pilot study

BACKGROUND

Adopting compensatory walking mechanisms by people with foot drop due to traumatic injury of the peroneal nerve costs altered gait kinetics and kinematics. Therefore, orthoses are generally recommended to minimize the deployment of compensatory gait mechanisms.

OBJECTIVES

To investigate the immediate effects of a low-cost, Neoprene Ankle-Foot Orthosis (NAFO) and the thermoplastic ankle-foot orthosis (AFO) with the shoe-only condition on kinematics and kinetics of gait of people with foot drop following peroneal nerve traumatic injury.

METHODS

Seven people with foot drop due to traumatic injury of the peroneal nerve were included in this study. The gait kinematics and kinetics of the participants were investigated in three different conditions: shoe-only, AFO + shoe, and NAFO + shoe using a six-camera, motion-analysis system, and a force platform. A Friedman two-way ANOVA by ranks model was employed to compare different testing conditions.

RESULTS

The ankle angle at the initial contact was significantly different between shoe-only condition and AFO (p < 0.00). The plantarflexion angle in both orthotic designs was reduced significantly compared to the shoe-only condition (p < 0.00). The maximum ankle dorsiflexion angle during the stance phase and maximum knee flexion angle during the stance and swing phases were not statistically significant for all testing conditions (p > 0.00). A significant difference was observed for the 1st-rise of the ground reaction force's vertical component between the NAFO and the AFO (p < 0.00). Likewise, a significant difference was observed for the 2nd-rise of the ground reaction force's vertical component between the NAFB and the AFO (p < 0.00).

CONCLUSION

Both orthotic interventions could control the ankle-foot complex during the gait and reduce the employment of compensatory gait mechanisms.

Commonly Used Types and Recent Development of Ankle-Foot Orthosis: A Narrative Review

(1) Background: ankle-foot orthosis (AFO) is the most commonly prescribed orthosis to patients with foot drop, and ankle and foot problems. In this study, we aimed to review the commonly used types of AFO and introduce the recent development of AFO. (2) Methods: narrative review. (3) Results: AFO prevents the foot from being dragged, provides a clearance between the foot and the ground in the swinging phase of gait, and maintains a stable posture by allowing heel contact with the ground during the stance phase. In clinical practice, the most commonly used AFO include plastic AFO, walking boot, UD-Flex, and carbon fiber AFO. In addition, for compensating the demerits of these conventional AFOs, new types of AFOs, including AF Servo, TurboMed, three-dimensionally printed AFO, and AFO made from kenaf composites, were developed. (4) Conclusions: we think that our review can guide clinicians in selecting and prescribing the appropriate AFO for each patient in accordance with their specific physical conditions.

Effect of Ankle Torque on the Ankle-Foot Orthosis Joint Design Sustainability

The ankle joint of a powered ankle–foot orthosis (PAFO) is a prominent component, as it must withstand the dynamic loading conditions during its service time, while delivering all the functional requirements such as reducing the metabolic effort during walking, minimizing the stress on the user’s joint, and improving the gait stability of the impaired subjects. More often, the life of an AFO is limited by the performance of its joint; hence, a careful design consideration and material selection are required to increase the AFO’s service life. In the present work, a compact AFO joint was designed based on a worm gear mechanism with steel and brass counterparts due to the fact of its large torque transfer capability in a single stage, enabling a compact joint. Further, it provided an added advantage of self-locking due to the large friction that prevents backdrive, which is beneficial for drop-foot recovery. The design was verified using nonlinear finite element analysis for maximum torque situations at the ankle joint during normal walking. The results indicate stress levels within its design performance; however, it is recommended to select high-grade structural steel for the ankle shaft as the highest stresses in AFO were located on it.

Muscles Affecting Minimum Toe Clearance

The aim of this study was to investigate how the anterior and posterior muscles in the shank (Tibialis Anterior, Gastrocnemius Lateralis and Medialis), influence the level of minimum toe clearance (MTC). With aging, MTC deteriorates thus, greatly increasing the probability of falling or tripping. This could result in injury or even death. For this study, muscle activity retention taping (MART) was used on young adults, which is an accepted method of simulating a poor MTC—found in elderly gait. The subject's muscle activation was measured using surface electromyography (SEMG), and the kinematic parameters (MTC, knee and ankle joint angles) were measured using an optical motion capture system. Our results indicate that MART produces significant reductions in MTC (P < α), knee flexion (P < α) and ankle dorsiflexion (P < α), as expected. However, the muscle activity increased significantly, contrary to the expected result (elderly individuals should have lower muscle activity). This was due to the subject's muscle conditions (healthy and strong), hence the muscles worked harder to counteract the external restriction. Yet, the significant change in muscle activity (due to MART) proves that the shank muscles do play an important role in determining the level of MTC. The Tibialis Anterior had the highest overall muscle activation, making it the primary muscle active during the swing phase. With aging, the shank muscles (specifically the Tibialis Anterior) would weaken and stiffen, coupled with a reduced joint range of motion. Thus, ankle-drop would increase—leading to a reduction in MTC.

The comparison of the effect of innovative designed storing-restoring hybrid passive AFO versus posterior leaf spring AFO on ankle joint kinematic in drop foot patients: A case series using a single subject design

Background: Drop foot syndrome is a disorder characterized by foot slapping after the initial contact and foot-dragging during the swing phase. Passive and hybrid passive ankle foot orthoses (AFOs) are often prescribed in these patients; however, the effects of these AFO designs on kinematic parameters during gait are unclear. The aim of this study was to compare the effect of innovative designed storing-restoring hybrid passive AFOs versus posterior leaf spring AFO on ankle joint kinematics in drop foot patients.

Methods: The present study was a case series where a single case and 3 cases with drop foot syndrome were recruited. This study was designed in 2 phases: the baseline phase with their PLS AFOs and an intervention phase in which innovative designed AFO were assessed. Each phase included 5 measurement sessions which were performed in 5 consecutive weeks. The celeration line method was used to detect the significant differences between the phases.

Results: The results of this study showed a significant increase in the kinematic angles parameters at the initial contact, the loading response, the mid stance, terminal stance, pre swing, initial swing, mid swing, and terminal swing with the innovative designed AFO than with PLS AFO (p<0.05).

Conclusion: The results of the present study suggested that use of the innovative designed AFO may have a positive effect on ankle joint kinematics parameters in people with drop foot.

A Clinical Practice Guideline for the Use of Ankle-Foot Orthoses and Functional Electrical Stimulation Post-Stroke

BACKGROUND

Level of ambulation following stroke is a long-term predictor of participation and disability. Decreased lower extremity motor control can impact ambulation and overall mobility. The purpose of this clinical practice guideline (CPG) is to provide evidence to guide clinical decision-making for the use of either ankle-foot orthosis (AFO) or functional electrical stimulation (FES) as an intervention to improve body function and structure, activity, and participation as defined by the International Classification of Functioning, Disability and Health (ICF) for individuals with poststroke hemiplegia with decreased lower extremity motor control.

METHODS

A review of literature published through November 2019 was performed across 7 databases for all studies involving stroke and AFO or FES. Data extracted included time post-stroke, participant characteristics, device types, outcomes assessed, and intervention parameters. Outcomes were examined upon initial application and after training. Recommendations were determined on the basis of the strength of the evidence and the potential benefits, harm, risks, or costs of providing AFO or FES.

RESULTS/DISCUSSION

One-hundred twenty-two meta-analyses, systematic reviews, randomized controlled trials, and cohort studies were included. Strong evidence exists that AFO and FES can each increase gait speed, mobility, and dynamic balance. Moderate evidence exists that AFO and FES increase quality of life, walking endurance, and muscle activation, and weak evidence exists for improving gait kinematics. AFO or FES should not be used to decrease plantarflexor spasticity. Studies that directly compare AFO and FES do not indicate overall superiority of one over the other. But evidence suggests that AFO may lead to more compensatory effects while FES may lead to more therapeutic effects. Due to the potential for gains at any phase post-stroke, the most appropriate device for an individual may change, and reassessments should be completed to ensure the device is meeting the individual's needs.

LIMITATIONS

This CPG cannot address the effects of one type of AFO over another for the majority of outcomes, as studies used a variety of AFO types and rarely differentiated effects. The recommendations also do not address the severity of hemiparesis, and most studies included participants with varied baseline ambulation ability.

SUMMARY

This CPG suggests that AFO and FES both lead to improvements post-stroke. Future studies should examine timing of provision, device types, intervention duration and delivery, longer term follow-up, responders versus nonresponders, and individuals with greater impairments.

DISCLAIMER

These recommendations are intended as a guide for clinicians to optimize rehabilitation outcomes for people with poststroke hemiplegia who have decreased lower extremity motor control that impacts ambulation and overall mobility.A Video Abstract is available as supplemental digital content from the authors (available at: http://links.lww.com/JNPT/A335).

Reliability of Bi-Axial Ankle Stiffness Measurement in Older Adults

This study involves measurements of bi-axial ankle stiffness in older adults, where the ankle joint is passively moved along the talocrural and subtalar joints using a custom ankle movement trainer. A total of 15 elderly individuals participated in test-retest reliability measurements of bi-axial ankle stiffness at exactly one-week intervals for validation of the angular displacement in the device. The ankle's range of motion was also compared, along with its stiffness. The kinematic measurements significantly corresponded to results from a marker-based motion capture system (dorsi-/plantar flexion: r = 0.996; inversion/eversion: r = 0.985). Bi-axial ankle stiffness measurements showed significant intra-class correlations (ICCs) between the two visits for all ankle movements at slower (2.14°/s, ICC = 0.712) and faster (9.77°/s, ICC = 0.879) speeds. Stiffness measurements along the talocrural joint were thus shown to have significant negative correlation with active ankle range of motion (r = -0.631, p = 0.012). The ankle movement trainer, based on anatomical characteristics, was thus used to demonstrate valid and reliable bi-axial ankle stiffness measurements for movements along the talocrural and subtalar joint axes. Reliable measurements of ankle stiffness may help clinicians and researchers when designing and fabricating ankle-foot orthosis for people with upper-motor neuron disorders, such as stroke.

Effects of wearable ankle robotics for stair and over-ground training on sub-acute stroke: a randomized controlled trial

BACKGROUND

Wearable ankle robotics could potentially facilitate intensive repetitive task-specific gait training on stair environment for stroke rehabilitation. A lightweight (0.5 kg) and portable exoskeleton ankle robot was designed to facilitate over-ground and stair training either providing active assistance to move paretic ankle augmenting residual motor function (power-assisted ankle robot, PAAR), or passively support dropped foot by lock/release ankle joint for foot clearance in swing phase (swing-controlled ankle robot, SCAR). In this two-center randomized controlled trial, we hypothesized that conventional training integrated with robot-assisted gait training using either PAAR or SCAR in stair environment are more effective to enhance gait recovery and promote independency in early stroke, than conventional training alone.

METHODS

Sub-acute stroke survivors (within 2 months after stroke onset) received conventional training integrated with 20-session robot-assisted training (at least twice weekly, 30-min per session) on over-ground and stair environments, wearing PAAR (n = 14) or SCAR (n = 16), as compared to control group receiving conventional training only (CT, n = 17). Clinical assessments were performed before and after the 20-session intervention, including functional ambulatory category as primary outcome measure, along with Berg balance scale and timed 10-m walk test.

RESULTS

After the 20-session interventions, all three groups showed statistically significant and clinically meaningful within-group functional improvement in all outcome measures (p < 0.005). Between-group comparison showed SCAR had greater improvement in functional ambulatory category (mean difference + 0.6, medium effect size 0.610) with more than 56% independent walkers after training, as compared to only 29% for CT. Analysis of covariance results showed PAAR had greater improvement in walking speed than SCAR (mean difference + 0.15 m/s, large effect size 0.752), which was in line with the higher cadence and speed when wearing the robot during the 20-session robot-assisted training over-ground and on stairs.

CONCLUSIONS

Robot-assisted stair training would lead to greater functional improvement in gait independency and walking speed than conventional training in usual care. The active powered ankle assistance might facilitate users to walk more and faster with their paretic leg during stair and over-ground walking.

TRIAL REGISTRATION

ClinicalTrials.gov NCT03184259. Registered on 12 June 2017.

Positional difference of malleoli-midpoint from three-dimensional geometric centre of rotation of ankle and its effect on ankle joint kinetics

BACKGROUNDS

Joint kinetic calculations are sensitive to joint centre locations. Although geometric hip and knee joint centre/axis are generally developed, the ankle joint centre (AJC) is conventionally defined as the midpoint between the malleolus lateralis and medialis (AJC_MID) in most gait analyses.

RESEARCH QUESTION

We examined the positional difference of the AJC_MID from the geometric centre of rotation (AJC_FUN) and its effect on the ankle joint kinetics in representative human gaits.

METHODS

In the first experiment, we calculated the AJC_FUN and indicated its location on the ankle MRI in 14 (seven male and seven female) participants. In the second experiment, we compared ankle kinematics/kinetics based on AJC_FUN and AJC_MID during walking and hopping at 2.6 Hz in 17 (nine male and eight female) participants.

RESULTS

In both experiments, AJC_FUN was located at positions significantly medial (-9.2 ± 5.4 mm and -10.1 ± 4.4 mm) and anterior (17.0 ± 7.4 mm and 15.3 ± 5.2 mm) from the AJC_MID. Furthermore, the AJC_MID underestimated peak dorsiflexion (AJC_MID/AJC_FUN: 52.6 ± 17.1%) and inversion (AJC_MID/AJC_FUN: 62.2 ± 11.5%) torques and their durations in walking. Additionally, AJC_MID overestimated the plantar flexion torque in both gait modes [AJC_MID/AJC_FUN: 111.3 ± 4.8% (walking) and 112.7 ± 6.3% (hopping)].

SIGNIFICANCE

We therefore concluded that the positional difference between the geometric and landmark-based AJC definitions significantly affected ankle kinetics, thereby indicating that the functional method should be used for defining AJC for gait analysis.

Design and Preliminary Evaluation of a New Ankle Foot Orthosis on Kinetics and Kinematics parameters for Multiple Sclerosis Patients

Background:

The damage of the central nervous system due to Multiple Sclerosis (MS) leads to many walking disorders in this population. However, current ankle-foot orthoses prescribed for improving walking disorders for these patients are not clinically cost-efficient.

Objective:

This study aimed to design and fabricate a dynamic ankle foot orthosis and a new spring-damper joint mechanism that could adapt the walking problems of MS patients and evaluate the immediate effect of the new orthosis on the speed, range of motion, moment, total work and ground reaction force during walking.

Material and Methods:

In this case-series study, after the design and fabrication of a new orthosis, the kinetics and kinematics of walking of four patients with MS were assessed in a case series study.

Results:

Walking speed improved with the new orthosis in two participants. The sagittal range of motion (ROM) increased for most of the participants. The sagittal moments increased for hip, knee and ankle joints in most of the measurements. The total joint work showed noticeable difference in the ankle joint. The increased values of vertical component of the ground reaction force (VGRF) were negligible and the increase in the impulse of VGRF was noticeable for only one participant.

Conclusion:

The new orthosis had positive effects kinetic and kinematic parameters of walking such as the increased velocity by two subjects and also a more normal sagittal ROM, moment and work, suggesting the potential usefulness of the new orthotic device for MS population.

Role of the newly designed Ankle Foot Orthosis on balance related parametersin drop foot post stroke patients

BACKGROUND

Passive and hybrid passive ankle foot orthoses (AFOs) are often prescribed in post stroke drop foot; however, the effects of these AFOs on balance related parameters in these patients seem unclear. Accordingly, the aim of current study was to evaluate the role of the newly designed hybrid passive and Posterior Leaf Spring (PLS) AFOs on balance related parameters including: self-reported balance confidence (ABC), Timed Up and Go Test (TUG) and Berg Balance Scale (BBS) in post stroke drop foot patients.

METHODS

Fifteen post stroke drop foot patients were recruited in current study. Then, ABC, TUG and BBS were assessed with newly designed AFO and PLS AFO.

RESULTS

The results of this study were shown a significant improvement in ABC, TUG and BBS scores with the newly designed AFO than PLS AFO (p < 0.05).

CONCLUSION

This study suggested that the newly designed AFO was improved the balance related parameters than PLS AFO.

Design and evaluation of a modularized ankle-foot orthosis with quick release mechanism

Ankle foot orthosis (AFO) stiffness affects ankle range of motion but can also provide energy storage and return to improve mobility. To perform multiple activities during the day, a person may want to change their AFO stiffness to meet their activity's demand. Carrying multiple AFOs and changing AFOs is inconvenient and could discourage users from engaging in multiple activities. This project will develop a new quick-release mechanism (QRM) that allows users to easily change posterior strut elements to change AFO stiffness. The QRM attaches to the AFO and requires no tools to operate. The proposed QRM includes a quick-release key, weight-bearing pin, receptacle anchor, and immobilization pin. A prototype was modelled with SolidWorks and simulated with SolidWorks Simulation. The QRM was designed to have no mechanical failure during intense activities such as downhill walking and jogging. Unlike a solid screw connection, the QRM needed an additional part to eliminate unsecured motion related to clearance between the quick release key and receptacle anchor. Mechanical test results and measurement data proved no deformation on each part after mechanical testing.Clinical Relevance- The quick release AFO has the potential to improve user's activities range by tuning from stiffness free mode to high stiffness mode.

The effect of articulated AFO with hydra pneumatic damper in biomechanical characteristic of drop foot: A pilot study

Background: Ankle Foot Orthosis (AFOs) are frequently prescribed in the management of drop-foot patients. However, few studies have examined the benefits of different design of Ankle Foot Orthosis with extra elements like dampers or springs. Therefore, the objective of this study was to investigate the efficacy of articulated Ankle Foot Orthosis with Hydra pneumatic damper, in kinetic, kinematic and spatiotemporal parameters of drop foot patients. Methods: Ten drop foot patients were recruited for this study, walked at self-selected comfortable speed. A three-dimensional motion analysis, were used for obtaining kinetic, spatio-temporal and kinematic gait parameters. Results: The articulated Ankle Foot Orthosis with Hydra pneumatic damper was significantly improved speed, cadence, step length of walking (p<0.005). Furthermore, the peak and mean of moment, push off velocity and energy storing/returning were significantly improved by articulated Ankle Foot Orthosis with Hydra pneumatic damper (p<0.005). Conclusion: The newly designed articulated Ankle Foot Orthosis with Hydra pneumatic damper improved the ankle moment in at the loading response, power generation and the ankle range in drop foot patient.

Novel design for a dynamic ankle foot orthosis with motion feedback used for training in patients with hemiplegic gait: a pilot study

BACKGROUND

We designed a novel ankle foot orthosis (AFO), namely, ideal training AFO (IT-AFO), with motion feedback on the hemiparetic lower limb to improve ambulation in individuals with stroke-related hemiplegia. We, therefore sought to compare the kinematic parameters of gait between IT-AFO with and without dynamic control and conventional anterior-type AFO or no AFO.

METHODS

Gait parameters were measured using the RehaWatch® system in seven individuals with hemiplegia (mean 51.14 years). The parameters were compared across four conditions: no AFO, conventional anterior AFO, IT-AFO without dynamic control, and IT-AFO with dynamic control, with three trials of a 10-m walk test for each.

RESULTS

The dorsiflexion angle increased during the swing phase when the IT-AFO was worn, and it was larger with dynamic control. These data can confirm drop foot improvement; however, the difference between the parameters with- and without-AFO control conditions was not significant in the swing phase. The IT-AFO with or without dynamic control enhanced the loading response to a greater extent between the hemiparetic and unaffected lower limbs than conventional AFO or no AFO. The duration of the stance phase on the hemiparetic lower limb was also longer when using IT-AFO with and without dynamic control than that when using conventional AFO, which improved asymmetry. User comfort and satisfaction was greater with IT-AFO than with the other conditions.

CONCLUSIONS

The IT-AFO with dynamic control improved gait pattern and weight shifting to the hemiparetic lower limb, reducing gait asymmetry. The difference with and without dynamic control of IT-AFO is not statistically significant, and it is limited by sample size. However, this study shows the potential of IT-AFO in applying positive motion feedback with gait training.

TRIAL REGISTRATION

Taipei Medical University-Joint Institutional Review Board. N201510010 . Registered 12 February 2015. http://ohr.tmu.edu.tw/main.php .

Functional electrical stimulation of the peroneal nerve improves post-stroke gait speed when combined with physiotherapy. A systematic review and meta-analysis

BACKGROUND

Functional electrical stimulation (FES) applied to the paretic peroneal nerve has positive clinical effects on foot drop secondary to stroke.

OBJECTIVE

To evaluate the effectiveness of FES applied to the paretic peroneal nerve on gait speed, active ankle dorsiflexion mobility, balance, and functional mobility.

METHODS

Electronic databases were searched for articles published from inception to January 2020. We included randomized controlled trials or crossover trials focused on determining the effects of FES combined or not with other therapies in individuals with foot drop after stroke. Characteristics of studies, participants, comparison groups, interventions, and outcomes were extracted. Statistical heterogeneity was assessed with the I² statistic.

RESULTS

We included 14 studies providing data for 1115 participants. FES did not enhance gait speed as compared with conventional treatments (i.e., supervised/unsupervised exercises and regular activities at home). FES combined with supervised exercises (i.e., physiotherapy) was better than supervised exercises alone for improving gait speed. We found no effect of FES combined with unsupervised exercises and inconclusive effects when FES was combined with regular activities at home. When FES was compared with conventional treatments, it improved ankle dorsiflexion, balance and functional mobility, albeit with high heterogeneity for these last 2 outcomes.

CONCLUSIONS

This meta-analysis revealed low quality of evidence for positive effects of FES on gait speed when combined with physiotherapy. FES can improve ankle dorsiflexion, balance, and functional mobility. However, considering the low quality of evidence and the high heterogeneity, these results must be interpreted carefully.

Design and Evaluation of an Articulated Ankle Foot Orthosis with Plantarflexion Resistance on the Gait: a Case Series of 2 Patients with Hemiplegia

Ankle-foot orthoses (AFOs) have been described to have positive effects on the gait biomechanics in stroke patients. The plantarflexion resistance of an AFO is considered important for hemiplegic patients, but the evidence is still limited. The purpose of this case series was to design and evaluate the immediate effect of an articulated AFO on kinematics and kinetics of lower-limb joints in stroke patients. The articulated AFO with the adjustment of plantarflexion resistance was designed. The spring generates a plantarflexion resistance of the ankle joint at initial stance phase. The efficacy of orthosis was evaluated on two stroke patients in 2 conditions: without an AFO and with the AFO. Results showed the immediate improvements for walking speed, stride length and angular changes of dorsiflexion of the paretic ankle joint during a gait cycle of both subjects using the AFO compared with barefoot walking. The AFO also was able to reduce the paretic knee extension in the single-support phase of the stance and increase the vertical COM displacement during stance phase on the affected leg. In conclusion, the designed AFO affect not only the movement of the ankle joint but also the movements of the knee joint and the vertical COM height. These changes indicate improvement of the first and the second rockers and swing phase gait but not third rocker function. Further investigation is recently underway to compare its effect compared with other AFOs on the gait parameters of hemiplegic patients.

[Orthopedic services as a tool of medical rehabilitation of patients with foot drop syndrome]

OBJECTIVE

To study the features of the rehabilitation of patients with foot drop syndrome and to develop recommendations for the appointment of technical means of rehabilitation (TMR) for this pathology.

MATERIAL AND METHODS

Retrospective analysis of the survey data of 375 patients in need of lower limb orthosis was carried out. General clinical and biomechanical methods were used to study the disturbances of statodynamic function of the musculoskeletal system.

RESULTS AND CONCLUSION

The results confirm that patients with foot drop syndrome have disturbances of support, stability, symmetry and rhythmicity of walking and, as a result, a significant deterioration in the quality of life. It has been established that the patients is not fully provided with orthoses and orthopedic shoes appointed to compensate for impaired function. Practitioners and rehabilitation specialists have difficulties in substantiating the needs and recommendations of TMR for a particular patient. The presented medical and technical requirements for product designs, the methodology for determining the need for them and recommendations for the appointment of TMR will contribute to the successful rehabilitation of patients with foot drop syndrome.

Ankle-foot orthosis design between the tradition and the computerized perspectives

This study focuses on the drop foot case related to hyperthyroidism of the ankle joint resulting in the relaxation of the toes during walking. This condition requires treatment using an ankle-foot orthosis. Traditional orthosis techniques lack precision and depend on the skill of the fabricator. This research aims to make a bias in ankle-foot orthosis design and analysis methods, where a complete methodology of numerical design and testing has been proposed using advanced engineering software. A numerical model of the patient's foot was generated and used to design an ankle-foot orthosis model using SolidWorks. The designed model was mechanically analyzed by the finite element method using ANSYS Workbench 16.1 under different static and dynamic loading conditions. The ankle-foot orthosis model was numerically designed and analyzed before the manufacturing process. This is believed to reduce time and material loss and foster the use of numerical models in biomedical applications. This study suggests focusing on the design and analysis of orthoses according to the patient's measurements. This is expected to increase the comfort and raise the level of treatment. Numerical design methods also enable precise manufacturing using computerized devices such as three-dimensional printers.

Control Reference Parameter for Stance Assistance Using a Passive Controlled Ankle Foot Orthosis—A Preliminary Study

This paper aims to present a preliminary study of control reference parameters for stance assistance among different subjects and walking speeds using a passive-controlled ankle foot orthosis. Four young male able-bodied subjects with varying body mass indexes (23.842 ± 4.827) walked in three walking speeds of 1, 3, and 5 km/h. Two control references, average ankle torque (aMa), and ankle angular velocity (aω), which can be implemented using a magnetorheological brake, were measured. Regression analysis was conducted to identify suitable control references in the three different phases of the stance. The results showed that aω has greater correlation (p) with body mass index and walking speed compared to aMa in the whole stance phase (p1(aω) = 0.666 > p1(aMa) = 0.560, p2(aω) = 0.837 > p2(aMa) = 0.277, and p3(aω) = 0.839 > p3(aMa) = 0.369). The estimation standard error (Se) of the aMa was found to be generally higher than of aω (Se1(aMa) = 2.251 > Se1(aω) = 0.786, Se2(aMa) = 1.236 > Se2(aω) = 0.231, Se3(aMa) = 0.696 < Se3(aω) = 0.755). Future studies should perform aω estimation based on body mass index and walking speed, as suggested by the higher correlation and lower standard error as compared to aMa. The number of subjects and walking speed scenarios should also be increased to reduce the standard error of control reference parameters estimation.

Wearable Ankle Robots in Post-stroke Rehabilitation of Gait: A Systematic Review

Background: Stroke causes weak functional mobility in survivors and affects the ability to perform activities of daily living. Wearable ankle robots are a potential intervention for gait rehabilitation post-stroke. Objective: The aim of this study is to provide a systematic review of wearable ankle robots, focusing on the overview, classification and comparison of actuators, gait event detection, control strategies, and performance evaluation. Method: Only English-language studies published from December 1995 to July 2018 were searched in the following databases: PubMed, EMBASE, Web of Science, Scopus, IEEE Xplore, Science Direct, SAGE journals. Result: A total of 48 articles were selected and 97 stroke survivors participated in these trials. Findings showed that few comparative trials were conducted among different actuators or control strategies. Moreover, mixed sensing technology which combines kinematic with kinetic information was effective in detecting motion intention of stroke survivors. Furthermore, all the selected clinical studies showed an improvement in the peak dorsiflexion degree of the swing phase, propulsion on the paretic side during push-off, and further enhanced walking speed after a period of robot-assisted ankle rehabilitation training. Conclusions: Preliminary findings suggest that wearable ankle robots have certain clinical benefits for the treatment of hemiplegic gait post-stroke. In the near future, a multicenter randomized controlled clinical trial is extremely necessary to enhance the clinical effectiveness of wearable ankle robots.

Design of a Low Profile, Unpowered Ankle Exoskeleton That Fits Under Clothes: Overcoming Practical Barriers to Widespread Societal Adoption

Here, we present the design of a novel unpowered ankle exoskeleton that is low profile, lightweight, quiet, and low cost to manufacture, intrinsically adapts to different walking speeds, and does not restrict non-sagittal joint motion; while still providing assistive ankle torque that can reduce demands on the biological calf musculature. This paper is an extension of the previously-successful ankle exoskeleton concept by Collins, Wiggin, and Sawicki. We created a device that blends the torque assistance of the prior exoskeleton with the form-factor benefits of clothing. Our design integrates a low profile under-the-foot clutch and a soft conformal shank interface, coupled by an ankle assistance spring that operates in parallel with the user's calf muscles. We fabricated and characterized technical performance of a prototype through benchtop testing and then validated device functionality in two gait analysis case studies. To our knowledge, this is the first ankle plantarflexion assistance exoskeleton that could be feasibly worn under typical daily clothing, without restricting ankle motion, and without components protruding substantially from the shoe, leg, waist, or back. Our new design highlights the potential for performance-enhancing exoskeletons that are inexpensive, unobtrusive, and can be used on a wide scale to benefit a broad range of individuals throughout society, such as the elderly, individuals with impaired plantarflexor muscle strength, or recreational users. In summary, this paper demonstrates how an unpowered ankle exoskeleton could be redesigned to more seamlessly integrate into daily life, while still providing performance benefits for common locomotion tasks.

A Review on the Control of the Mechanical Properties of Ankle Foot Orthosis for Gait Assistance

In the past decade, advanced technologies in robotics have been explored to enhance the rehabilitation of post-stroke patients. Previous works have shown that gait assistance for post-stroke patients can be provided through the use of robotics technology in ancillary equipment, such as Ankle Foot Orthosis (AFO). An AFO is usually used to assist patients with spasticity or foot drop problems. There are several types of AFOs, depending on the flexibility of the joint, such as rigid, flexible rigid, and articulated AFOs. A rigid AFO has a fixed joint, and a flexible rigid AFO has a more flexible joint, while the articulated AFO has a freely rotating ankle joint, where the mechanical properties of the AFO are more controllable compared to the other two types of AFOs. This paper reviews the control of the mechanical properties of existing AFOs for gait assistance in post-stroke patients. Several aspects that affect the control of the mechanical properties of an AFO, such as the controller input, number of gait phases, controller output reference, and controller performance evaluation are discussed and compared. Thus, this paper will be of interest to AFO researchers or developers who would like to design their own AFOs with the most suitable mechanical properties based on their application. The controller input and the number of gait phases are discussed first. Then, the discussion moves forward to the methods of estimating the controller output reference, which is the main focus of this study. Based on the estimation method, the gait control strategies can be classified into subject-oriented estimations and phase-oriented estimations. Finally, suggestions for future studies are addressed, one of which is the application of the adaptive controller output reference to maximize the benefits of the AFO to users.

External neurolysis as a treatment for foot drop secondary to weight loss: a retrospective analysis of 200 cases

BACKGROUND

Peroneal nerve entrapment is the most common peripheral mononeuropathy of the lower limbs. Foot drop, a common presentation, leads to an impaired eversion and dorsiflexion of the foot. An intriguing observation is the occurrence of foot drop secondary to weight loss.

METHODS

A retrospective study of patients surgically treated for peroneal nerve entrapment was performed between January 1, 1995 and December 31, 2016, at the Department of Neurosurgery, Genk, Belgium. Out of a total of 421 patients, 200 patients with foot drop secondary to weight loss were included. For each subject, motor and sensory outcomes after external neurolysis were investigated. As a primary objective, we examined the postoperative outcomes of external neurolysis as a treatment for foot drop in patients with peroneal nerve entrapment at the fibular head secondary to weight loss. As a secondary objective, we analyzed the correlation between patient characteristics and the success rate of external neurolysis.

RESULTS

When defining success as a postoperative MRC score of 4 or 5, external neurolysis has a success rate of 85% in patients with foot drop secondary to weight loss. A significant difference (P = < 0.0001) between postoperative and preoperative MRC scores indicates that external neurolysis leads to significant improvement of motor function in patients with foot drop secondary to weight loss. A multiple logistic regression model showed that "preoperative MRC scores" and "duration of symptoms" were the only variables with an impact on postoperative MRC scores. Other variables such as "age," "gender," and "side of entrapment" had no significant impact on postoperative results.

CONCLUSIONS

Statistical analysis emphasizes the important role of external neurolysis in the treatment of peripheral peroneal nerve entrapment. Therefore, external neurolysis at the fibular head should be regarded as a very effective and safe procedure in patients with foot drop secondary to weight loss.

Design of an exoskeleton ankle robot for robot-assisted gait training of stroke patients

Lower Limb Exoskeleton robot that can facilitate stair walking is a big challenge, most systems could only provide level ground walking. In this study, a lightweight (0.5kg at ankle, 0.5kg at waist for control box) and autonomous exoskeleton Ankle Robot was proposed to provide power assistance for gait training of chronic stroke patients and it can facilitate three walking conditions in real-time: (1) level walking, (2) stair ascending, and (3) stair descending. Chronic stroke patients (n=3) with drop foot gait deficit and moderate motor impairment were recruited to evaluate the system under different walking conditions (Functional Ambulatory Category: FAC=4.7±0.5 and Fugl-Meyer Assessment for lower-extremity: FMA-LE=13.7±2.9). The system consisted of a specially designed carbon fiber AFO, servomotor, gear transmission system, IMU and force sensors, and control box. The IMU sensors embedded in the shank measured acceleration and angular velocity to identify distinct features in leg tilting angle and leg angular velocity between the three walking conditions. The results showed the powered ankle dorsiflexion assistance could reduce dropped foot of the stroke patients in swing phase and provide better gait pattern. A demo of the ankle robot will be conducted in the conference.

Randomized controlled trial of robot-assisted gait training with dorsiflexion assistance on chronic stroke patients wearing ankle-foot-orthosis

BACKGROUND

Robot-assisted ankle-foot-orthosis (AFO) can provide immediate powered ankle assistance in post-stroke gait training. Our research team has developed a novel lightweight portable robot-assisted AFO which is capable of detecting walking intentions using sensor feedback of wearer's gait pattern. This study aims to investigate the therapeutic effects of robot-assisted gait training with ankle dorsiflexion assistance.

METHODS

This was a double-blinded randomized controlled trial. Nineteen chronic stroke patients with motor impairment at ankle participated in 20-session robot-assisted gait training for about five weeks, with 30-min over-ground walking and stair ambulation practices. Robot-assisted AFO either provided active powered ankle assistance during swing phase in Robotic Group (n = 9), or torque impedance at ankle joint as passive AFO in Sham Group (n = 10). Functional assessments were performed before and after the 20-session gait training with 3-month Follow-up. Primary outcome measure was gait independency assessed by Functional Ambulatory Category (FAC). Secondary outcome measures were clinical scores including Fugl-Meyer Assessment (FMA), Modified Ashworth Scale (MAS), Berg Balance Scale (BBS), Timed 10-Meter Walk Test (10MWT), Six-minute Walk Test (SMWT), supplemented by gait analysis. All outcome measures were performed in unassisted gait after patients had taken off the robot-assisted AFO. Repeated-measures analysis of covariance was conducted to test the group differences referenced to clinical scores before training.

RESULTS

After 20-session robot-assisted gait training with ankle dorsiflexion assistance, the active ankle assistance in Robotic Group induced changes in gait pattern with improved gait independency (all patients FAC ≥ 5 post-training and 3-month follow-up), motor recovery, walking speed, and greater confidence in affected side loading response (vertical ground reaction force + 1.49 N/kg, peak braking force + 0.24 N/kg) with heel strike instead of flat foot touch-down at initial contact (foot tilting + 1.91°). Sham Group reported reduction in affected leg range of motion (ankle dorsiflexion - 2.36° and knee flexion - 8.48°) during swing.

CONCLUSIONS

Robot-assisted gait training with ankle dorsiflexion assistance could improve gait independency and help stroke patients developing confidence in weight acceptance, but future development of robot-assisted AFO should consider more lightweight and custom-fit design.

TRIAL REGISTRATION

ClinicalTrials.gov NCT02471248 . Registered 15 June 2015 retrospectively registered.

Application of the Superelastic NiTi Spring in Ankle Foot Orthosis (AFO) to Create Normal Ankle Joint Behavior

Hinge-based Ankle Foot Orthosis (HAFO) is one of the most common non-surgical solutions for the foot drop. In conventional HAFOs, the ankle joint is almost locked, and plantar flexion is restricted due to the high stiffness of the hinge mechanism. This often leads to a rigid walking gate cycle, poor muscle activity, and muscle atrophy. Since the ankle torque-angle loop has a non-linear profile, the use of a superelastic NiTi spring within the hinge, due to its nonlinear behavior, could recreate a close-to-normal stiffness of the normal ankle joint, which, in turn, could create a more natural walk. The focus of this study is to evaluate the performance of a superelastic NiTi spring versus a conventional Stainless Steel spring in a hinge mechanism of a custom-fit HAFO. To this aim, a custom-fit HAFO was fabricated via the fast casting technique. Then, motion analysis was performed for two healthy subjects (Case I and Case II): (i) subjects with bare foot; (ii) subjects wearing a conventional HAFO with no spring; (iii) subjects wearing a conventional Stainless Steel-based HAFO; and (iv) subjects wearing a NiTi spring-based HAFO. The data related to the ankle angle and the amount of moment applied to the ankle during walking were recorded using Cortex software and used for the evaluations. Finally, Finite Element Analysis (FEA) was performed to evaluate the safety of the designed HAFO. The NiTi spring offers a higher range of motion (7.9 versus 4.14 degree) and an increased level of moment (0.55 versus 0.36 N·m/kg). Furthermore, a NiTi spring offers an ankle torque-angle loop closer to that of the healthy subjects.

Rigid Ankle Foot Orthosis Deteriorates Mediolateral Balance Control and Vertical Braking during Gait Initiation

Rigid ankle-foot orthoses (AFO) are commonly used for impeding foot drop during the swing phase of gait. They also reduce pain and improve gait kinematics in patients with weakness or loss of integrity of ankle-foot complex structures due to various pathological conditions. However, this comes at the price of constraining ankle joint mobility, which might affect propulsive force generation and balance control. The present study examined the effects of wearing an AFO on biomechanical variables and electromyographic activity of tibialis anterior (TA) and soleus muscles during gait initiation (GI). Nineteen healthy adults participated in the study. They initiated gait at a self-paced speed with no ankle constraint as well as wearing an AFO on the stance leg, or bilaterally. Constraining the stance leg ankle decreased TA activity ipsilaterally during the anticipatory postural adjustment (APA) of GI, and ipsilateral soleus activity during step execution. In the sagittal plane, the decrease in the stance leg TA activity reduced the backward displacement of the center of pressure (CoP) resulting in a reduction of the forward velocity of the center of mass (CoM) measured at foot contact (FC). In the frontal plane, wearing the AFO reduced the displacement of the CoP in the direction of the swing leg during the APA phase. The mediolateral velocity of the CoM increased during single-stance prompting a larger step width to recover balance. During step execution, the CoM vertical downward velocity is normally reduced in order to lessen the impact of the swing leg with the floor and facilitates the rise of the CoM that occurs during the subsequent double-support phase. The reduction in stance leg soleus activity caused by constraining the ankle weakened the vertical braking of the CoM during step execution. This caused the absolute instantaneous vertical velocity of the CoM at FC to be greater in the constrained conditions with respect to the control condition. From a rehabilitation perspective, passively- or actively-powered assistive AFOs could correct for the reduction in muscle activity and enhance balance control during GI of patients.

Investigation and management of IgM and Waldenström-associated peripheral neuropathies: recommendations from the IWWM-8 consensus panel

Paraproteinaemic neuropathies are a heterogeneous group of disorders most frequently associated with IgM monoclonal gammopathies including Waldenström macroglobulinaemia (WM). Their consequences are significant for affected patients, and their management challenging for their physicians. The variability in clinical presentation and time course hamper classification and management. The indications for invasive investigations such as cerebrospinal fluid analysis, nerve conduction tests and sensory nerve biopsies are unclear, and the optimum way to measure clinical response to treatment unknown. When to intervene and and how to treat, also present challenges to physicians. As part of its latest deliberations at the International Workshops on WM (IWWM) in London, UK (August 2014), the IWWM8 panel have proposed a consensus approach to the diagnosis and management of peripheral neuropathies associated with IgM monoclonal gammopathies, including WM. Importantly, a consensus regarding the use of clinical outcome measures and recommended models of care for this group of patients is discussed, as well as appropriate treatment interventions.