Kinematic effects on gait of a newly designed ankle-foot orthosis with oil damper resistance: a case series of 2 patients with hemiplegia

Effects of ankle-foot orthosis on gait pattern and spatiotemporal indices during treadmill walking in hemiparetic stroke

Ankle-foot orthosis (AFO) is known to correct abnormal gait patterns and improve walking stability and speed in patients with hemiparesis. To quantify these benefits in post-stroke gait, a three-dimensional motion analysis of gait pattern was conducted. Forty patients with hemiparesis were enrolled. A three-dimensional motion analysis system was used to analyze patients' treadmill walking with/without an AFO. Outcome measures were 12 abnormal gait indices (forefoot contact, knee extensor thrust, retropulsion of the hip, flexed-knee gait, medial whip in the stance phase, circumduction gait, hip hiking, insufficient knee flexion during the swing phase, excessive lateral shifting of the trunk, contralateral vaulting, excessive hip external rotation, and posterior pelvic tilt), calculated using kinematic data and spatiotemporal indices, and the symmetry index of double-stance and single-stance time and step length. Forefoot contact (without AFO vs. with AFO: 71.0 vs. 65.8, P < 0.001), circumduction gait (65.0 vs. 57.9, P < 0.001), and contralateral vaulting (78.2 vs. 72.2, P = 0.003) were significantly reduced, whereas excessive hip external rotation (53.7 vs. 62.8, P = 0.003) significantly increased during walking with an AFO. Hip hiking (77.1 vs. 71.7) showed marginal reduction with the use of AFO ( P = 0.096). The absolute symmetry index of double-stance time (21.9 vs. 16.1, P = 0.014) significantly decreased during walking with an AFO. AFO effectively mitigates abnormal gait patterns typical of hemiparetic gait. A 3D motion analysis system with clinically oriented indices can help assess intervention efficacy for gait abnormalities.

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.

Passive Articulated and Non-Articulated Ankle-Foot Orthoses for Gait Rehabilitation: A Narrative Review

The aim of this work was to study the different types of passive articulated and non-articulated ankle-foot orthoses for gait rehabilitation in terms of working principles, control mechanisms, features, and limitations, along with the recent clinical trials on AFOs. An additional aim was to categorize them to help engineers and orthotists to develop novel designs based on this research. Based on selected keywords and their composition, a search was performed on the ISI Web of Knowledge, Google Scholar, Scopus, and PubMed databases from 1990 to 2022. Forty-two studies met the eligibility criteria, which highlighted the commonly used types and recent development of passive articulated and non-articulated ankle-foot orthoses for foot drop. Orthotists and engineers may benefit from the information obtained from this review article by enhancing their understanding of the challenges in developing an AFO that meets all the requirements in terms of ease of use, freedom of movement, and high performance at a relatively low cost.

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.

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.

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.

Optimized Design of a Variable Viscosity Link for Robotic AFO

Herein we present the development of a novel Ankle Foot Orthosis for gait support of people with foot-drop symptoms. The developed AFO uses an elastic link mechanism to brake the ankle joint during initial contact, thus mitigating foot-slap, and an integrated energy store-and-release mechanism to support toe lift in the swing phase, thus mitigating toe-drag. This paper presents improvements in the braking-holding power of the elastic link mechanism over its previous version, the torque-angle characteristics of the developed AFO with the renewed elastic link, and a pilot test with one person with foot-drop symptoms to verify the proposed functions of the developed AFO.

Major patterns of plantar flexion resistive torque during the gait cycle in healthy young adults wearing ankle foot orthoses with a plantar flexion stop: a pilot study

[Purpose] The Gait Judge System measures the plantar flexion resistive torque acting on the angle of the ankle joint, as well as the ankle joint itself, of the ankle-foot orthosis using a 1,000 Hz sampling frequency. This pilot study aimed to determine the characteristics of plantar flexion resistive torque acting on the double Klenzak ankle joint of the ankle-foot orthoses worn by healthy individuals. [Participants and Methods] Participants were eight healthy young adults (3 male, 5 female; mean age, 26.8 years old; mean height, 165 cm.; mean body weight, 56.3 kg). Plantar flexion resistive torques and angles of the ankle joint in gait cycles were measured with the Gait Judge System. Speed of gait was calculated using a ruler attached on the floor and the Gait Judge System video. We classified waveforms according to the existence of second peaks in the gait cycle. The correlations between parameters related to the plantar flexion resistive torque and the speed of gait were evaluated using Pearson's simple correlation analysis. [Results] The plantar flexion resistive torque showed two peaks: the first peak was at the loading response, measured at 17.4 Nm, and the second peak was at the pre-swing phase, measured at 10.9 Nm. However, the second peak was absent in three of the participants. The normalized second peak and the second peak/first peak ratio had a strong, positive correlation with the speed of gait. [Conclusion] The Gait Judge System revealed typical waveforms according to the parameters set in this study.

Study on the design development of a multi joint ankle foot orthosis

[Purpose] The purpose of this study was to investigate the effects of a newly designed multi joint ankle-foot orthosis on the gait and dynamic balance of stroke patients having foot drop. [Participants and Methods] This study was investigated 10 participants who were diagnosed with stroke. Patients were evaluated based on a 10-meter walk test, timed up and go test and Berg balance scale after each participant wore a plastic ankle-foot orthosis and a multi joint ankle-foot orthosis (AFO) that consisted of orthosis joints (having poster-stop joint and Klenzak joint functions). [Results] The 10-meter walk test, timed up and go test and Berg balance scale showed significant differences in the orthosis with the Klenzak joint function. [Conclusion] The appropriate use of Klenzak AFO of the newly designed multi joint AFO is expected to have a positive effect on improving the gait and balancing ability of stroke patients having foot drop.

The impact of ankle-foot orthoses on toe clearance strategy in hemiparetic gait: a cross-sectional study

BACKGROUND

Ankle-foot orthoses (AFOs) are frequently used to improve gait stability, toe clearance, and gait efficiency in individuals with hemiparesis. During the swing phase, AFOs enhance lower limb advancement by facilitating the improvement of toe clearance and the reduction of compensatory movements. Clinical monitoring via kinematic analysis would further clarify the changes in biomechanical factors that lead to the beneficial effects of AFOs. The purpose of this study was to investigate the actual impact of AFOs on toe clearance, and determine the best strategy to achieve toe clearance (including compensatory movements) during the swing phase.

METHODS

This study included 24 patients with hemiparesis due to stroke. The gait performance of these patients with and without AFOs was compared using three-dimensional treadmill gait analysis. A kinematic analysis of the paretic limb was performed to quantify the contribution of the extent of lower limb shortening and compensatory movements (such as hip elevation and circumduction) to toe clearance. The impact of each movement related to toe clearance was assessed by analyzing the change in the vertical direction.

RESULTS

Using AFOs significantly increased toe clearance (p = 0.038). The quantified limb shortening and pelvic obliquity significantly differed between gaits performed with versus without AFOs. Among the movement indices related to toe clearance, limb shortening was increased by the use of AFOs (p < 0.0001), while hip elevation due to pelvic obliquity (representing compensatory strategies) was diminished by the use of AFOs (p = 0.003). The toe clearance strategy was not significantly affected by the stage of the hemiparetic condition (acute versus chronic) or the type of AFO (thermoplastic AFOs versus adjustable posterior strut AFOs).

CONCLUSIONS

Simplified three-dimensional gait analysis was successfully used to quantify and visualize the impact of AFOs on the toe clearance strategy of hemiparetic patients. AFO use increased the extent of toe clearance and limb shortening during the swing phase, while reducing compensatory movements. This approach to visualization of the gait strategy possibly contributes to clinical decision-making in the real clinical settings.

TRIAL REGISTRATION

UMIN000028946 . Registered 31 August 2017 (retrospectively registered).

Effect of different designs of ankle-foot orthoses on gait in patients with stroke: A systematic review

BACKGROUND

Ankle foot orthoses (AFOs) are used to improve the gait of patients with stroke.

RESEARCH QUESTION

The current review aimed at evaluating the efficacy of different designs of AFOs and comparison between them on the gait parameters of individuals with hemiplegic stroke.

METHODS

The search strategy was based on the population intervention comparison outcome (PICO) method. A search was performed in PubMed, ISI Web of Knowledge, Scopus, Science Direct, and Google Scholar databases.

RESULTS

A total of 27 articles were found for the final evaluation. All types of AFOs had positive effects on ankle kinematic in the first rocker and swing phases, but not on knee kinematics in the swing phase, hip kinematics or the third rocker function. All trials, except two, assessed immediate or short-term effects only. The articulated passive AFO compared with the non-articulated passive AFO had better effects on some aspects of the gait of patients with hemiplegia following stroke, more investigations are needed in this regard though.

SIGNIFICANCE

An ankle-foot orthosis can immediately improve the dropped foot in the stance and swing phases. The effects of long-term usage and comparison among the different types of AFOs need to be evaluated.

The effect of newly designed multi joint ankle foot orthosis on the gait and dynamic balance of stroke patients with foot drop

[Purpose] The purpose of this study is to investigate the effect of the newly designed multi joint ankle-foot orthosis on the gait and dynamic balance of stroke patients having foot drop. [Subjects and Methods] This study was conducted with 15 subjects who were diagnosed with stroke. 10-meter walk test, functional reaching test and timed up and go test were measured after each subjects wore a plastic ankle-foot orthosis and a multi joint ankle-foot orthosis that consists of orthosis joints (having free joint, anterior-stop joint, poster-stop joint, and Klenzak joint functions). In the case of the newly developed multi joint ankle-foot orthosis, the experiments were performed using posterior-stop joint and Klenzak joint. [Results] 10-meter walk test, functional reaching test and timed up and go test showed significant differences in the orthosis using posterior joint-stop function and Klenzak joint function. [Conclusion] The appropriate use of the four functions of the newly designed multi joint ankle-foot orthosis is expected to have a positive effect on improving the gait and balancing ability of stroke patients having foot drop.

The effect of newly designed multi joint ankle foot orthosis on the gait and dynamic balance of stroke patients with foot drop

[Purpose] The purpose of this study is to investigate the effect of the newly designed multi joint ankle-foot orthosis on the gait and dynamic balance of stroke patients having foot drop. [Subjects and Methods] This study was conducted with 15 subjects who were diagnosed with stroke. 10-meter walk test, functional reaching test and timed up and go test were measured after each subjects wore a plastic ankle-foot orthosis and a multi joint ankle-foot orthosis that consists of orthosis joints (having free joint, anterior-stop joint, poster-stop joint, and Klenzak joint functions). In the case of the newly developed multi joint ankle-foot orthosis, the experiments were performed using posterior-stop joint and Klenzak joint. [Results] 10-meter walk test, functional reaching test and timed up and go test showed significant differences in the orthosis using posterior joint-stop function and Klenzak joint function. [Conclusion] The appropriate use of the four functions of the newly designed multi joint ankle-foot orthosis is expected to have a positive effect on improving the gait and balancing ability of stroke patients having foot drop.

Plantarflexor training affects propulsive force generation during gait in children with spastic hemiplegic cerebral palsy: a pilot study

[Purpose] The purpose of this preliminary study was to assess the trade-off relationship between the hip and ankle joints after plantarflexor training in children with spastic hemiplegic cerebral palsy (CP). [Subjects and Methods] Three boys aged 9, 10, and 13 years with spastic hemiplegic CP participated in the study. Gait analysis was performed using a three-dimensional motion analysis device and a floor reaction force detection device before and after plantarflexor training. Data on gait speed and stride length for both sides were collected. Peak hip and ankle powers in the sagittal plane and ankle-to-hip power ratio (A2/H3 ratio) were calculated. Plantarflexor training comprised heel raises and exercise band resistance at the participant’s home (3 times/week for 12 weeks). [Results] The A2/H3 ratio increased significantly on both sides in two of three subjects after training. Peak A2 power increased significantly on both sides in subject 3 and on the affected side of subject 2. Peak H3 power decreased significantly on the non-affected side of subjects 1 and 2. [Conclusion] This study confirmed that two of three subjects demonstrated a trade-off relationship between the hip and ankle joints during gait after plantarflexor training.

Changes in angular kinematics of the paretic lower limb at different orthotic angles of plantar flexion limitation of an ankle-foot-orthosis for stroke patients

[Purpose] An ankle-foot-orthosis (AFO) is an assistive brace that allows stroke patients to achieve an independent gait. Therefore, we examined whether or not the orthotic angle for plantar flexion limitation affects the kinematic parameters of the hip and knee joints on the affected side of patients with stroke. [Subjects and Methods] Fifteen patients with chronic hemiplegia were recruited for this study. Kinematic three-dimensional data was acquired, while patients walked along a walkway wearing AFOs under five different conditions of 0°, 5°, 10°, 15°, and 20° of plantar stop limitation angle in the orthotic joint. Peak angles of the hip and knee joints on the affected side were analyzed. [Results] At the peak angle of the knee joint, statistically significant differences were found only at mid-stance in the sagittal plane and the horizontal plane. However, no significant differences were observed among any of the orthotic limitation angles in the frontal plane. [Conclusion] According to the results, an orthotic limitation angle of more than 10° elicits changes in the knee joint angle at mid-stance in the sagittal and horizontal planes. This study provided basic data on postural changes of patients with stroke.

Immediate-term effects of use of an ankle-foot orthosis with an oil damper on the gait of stroke patients when walking without the device

BACKGROUND

An ankle-foot orthosis using an oil damper is designed to enable natural movement of the ankle joint. Wearing an ankle-foot orthosis using an oil damper has been demonstrated to assist the first rocker in stroke patients, but its effect on their gait when not wearing it is unclear.

OBJECTIVES

To determine the effect of use of ankle-foot orthosis using an oil damper on the gait of stroke patients with hemiparesis when not wearing the ankle-foot orthosis.

STUDY DESIGN

Crossover study.

METHODS

The gait of eight stroke patients in the chronic phase when not wearing an ankle-foot orthosis was measured, using a three-dimensional motion analysis system, before using the ankle-foot orthosis using an oil damper and then without and with using the ankle-foot orthosis using an oil damper after 3 weeks of use. Differences in gait were compared between the three measurement conditions.

RESULTS

Use of ankle-foot orthosis using an oil damper significantly decreased preswing time and significantly increased the positive ankle joint power in stance when not wearing the ankle-foot orthosis using an oil damper.

CONCLUSIONS

These changes indicate the promising therapeutic effects of ankle-foot orthosis using an oil damper use and suggest the ankle-foot orthosis using an oil damper's potential as a therapeutic device.

CLINICAL RELEVANCE

After 3 weeks of use of an ankle-foot orthosis using an oil damper, which assists the first rocker, the gait of stroke patients in the chronic phase when not wearing the ankle-foot orthosis using an oil damper was improved. Preswing time was significantly decreased and positive ankle joint power was significantly increased. The ankle-foot orthosis using an oil damper, which assists the first rocker function with natural movement of the ankle joint during gait, has the potential to improve the gait of stroke patients after immediate-term use.

The influence of ankle-foot orthosis stiffness on walking performance in individuals with lower-limb impairments

BACKGROUND

Passive-dynamic ankle-foot orthoses utilize stiffness to improve gait performance through elastic energy storage and return. However, the influence of ankle-foot orthosis stiffness on gait performance has not been systematically investigated, largely due to the difficulty of manufacturing devices with precisely controlled stiffness levels. Additive manufacturing techniques such as selective laser sintering have been used to successfully manufacture ankle-foot orthoses with controlled stiffness levels. The purpose of this study was to use passive-dynamic ankle-foot orthoses manufactured with selective laser sintering to identify the influence of orthosis stiffness on walking performance in patients with lower-limb neuromuscular and musculoskeletal impairments.

METHODS

Thirteen subjects with unilateral impairments were enrolled in this study. For each subject, one passive-dynamic ankle-foot orthosis with stiffness equivalent to the subject's clinically prescribed carbon fiber orthosis, one 20% more compliant and one 20% more stiff, were manufactured using selective laser sintering. Three-dimensional kinematic and kinetic data and electromyographic data were collected from each subject while they walked overground with each orthosis at their self-selected velocity and a controlled velocity.

FINDINGS

As the orthosis stiffness decreased, ankle range of motion and medial gastrocnemius activity increased while the knee became more extended throughout stance. Minimal changes in other kinematic, kinetic and electromyographic quantities were observed.

INTERPRETATION

Subjects effectively compensated for changes in ankle-foot orthosis stiffness with altered gastrocnemius activity, and the stiffness levels analyzed in this study had a minimal effect on overall walking performance.

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

Robotic technologies are being employed increasingly in the treatment of lower limb disabilities. Individuals suffering from stroke and other neurological disorders often experience inadequate dorsiflexion during swing phase of the gait cycle due to dorsiflexor muscle weakness. This type of pathological gait, mostly known as drop-foot gait, has two major complications, foot-slap during loading response and toe-drag during swing. Ankle foot orthotic (AFO) devices are mostly prescribed to resolve these complications. Existing AFOs are designed with or without articulated joint with various motion control elements like springs, dampers, four-bar mechanism, series elastic actuator, and so forth. This paper examines various AFO designs for drop-foot, discusses the mechanism, and identifies limitations and remaining design challenges. Along with two commercially available AFOs some designs possess promising prospective to be used as daily-wear device. However, the design and mechanism of AFO must ensure compactness, light weight, low noise, and high efficiency. These entailments present significant engineering challenges to develop a new design with wide consumer adoption.

Effects of plantar flexion resistive moment generated by an ankle-foot orthosis with an oil damper on the gait of stroke patients: a pilot study

BACKGROUND

An ankle-foot orthosis with an oil damper was previously developed to assist the first rocker function during gait, but the effects of the amount of resistive moment generated on gait have not been clarified.

OBJECTIVES

To measure the amount of resistive moment generated by the ankle-foot orthosis with an oil damper during gait and determine its effect on the gait of patients with stroke.

STUDY DESIGN

Preliminary cross-sectional study.

METHODS

The gait of four patients with stroke in the chronic phase was measured in four conditions: without an ankle-foot orthosis and with the ankle-foot orthosis with an oil damper generating three different amounts of resistive moment. Measurements were taken with a three-dimensional motion analysis system and a specially designed device to determine the resistive moment.

RESULTS

The resistive moment was observed in the former half in stance of the paretic limb, and its magnitude was less than 10 N m. Some gait parameters related to terminal stance and preswing were affected by the amount of resistive moment. The forward component of floor reaction force and the shank vertical angle showed peak values when the patients reported feeling most comfortable during gait.

CONCLUSION

Although the resistive moment generated by the ankle-foot orthosis with an oil damper was small, it was sufficient to alter gait.

CLINICAL RELEVANCE

To maximize the effectiveness of ankle-foot orthoses, it is necessary to know the effects of resistive moment on the gait of patients with stroke. The ankle-foot orthosis with an oil damper assists the first rocker function in gait and also affects the gait in a later phase in stance. The peak values of some gait parameters coincided with patients reporting gait to be most comfortable. It is important to know that ankle-foot orthosis with an oil damper assistance in the first rocker alters the weight acceptance on the paretic limb and affects the gait parameters related to propulsion ability in stance.

Experimental evaluation of a portable powered ankle-foot orthosis

Ankle-foot orthoses (AFOs) ameliorate the impact of impairments to the lower limb neuromuscular motor system that affect gait. Emerging technologies provide a vision for fully powered, untethered AFOs. The portable powered AFO (PPAFO) provides both plantarflexor and dorsiflexor torque assistance via a bi-directional pneumatic rotary actuator. The system uses a portable pneumatic power source (bottle of compressed CO(2)) and embedded electronics to control foot motion during level walking. Experimental data were collected to demonstrate functionality from two subjects with bilateral impairments to the lower legs. These data demonstrated the PPAFO's ability to provide functional assistance during gait. The stringent design requirements of light weight, small size, high efficiency and low noise make the creation of daily wear assist devices challenging; but once such devices appear, they will present new opportunities for clinical treatment of gait abnormalities.

Change of rocker function in the gait of stroke patients using an ankle foot orthosis with an oil damper: immediate changes and the short-term effects

BACKGROUND

An ankle foot orthosis (AFO) using an oil damper (AFO-OD) to assist the first rocker during gait was previously developed but the effect on the other rocker functions has not been clarified.

OBJECTIVES

The immediate and short-term effects on the gait of stroke patients with the AFO-OD were investigated from the viewpoint of the rocker function.

STUDY DESIGN

Crossover study.

METHODS

The gait of eight stroke patients in chronic phase without an AFO, with the AFO-OD, and the gait with AFO-OD after three weeks of continuous use and gait training were measured by 3D motion analysis.

RESULTS

Immediate changes observed on use of the AFO-OD were improvements in walking speed, the spatiotemporal parameters, and the angular change of dorsiflexion of the ankle joint. Three weeks of continuous AFO-OD use and gait training showed further improvements in walking speed and the spatiotemporal parameters as well as an increase in dorsiflexion angle and plantar flexor moment of the ankle joint of the paretic limb in stance.

CONCLUSIONS

These changes produced improvement of the second rocker function, but improvement of the third rocker was insufficient. Results show the importance of gait training to take full advantage of an AFO.

Effect of early compensation of distal motor deficiency by the Chignon ankle-foot orthosis on gait in hemiplegic patients: a randomized pilot study

Objective: To compare the effect of the Chignon ankle-foot orthosis on gait versus a standard ankle-foot orthosis.

Method: A multicentre randomized study was conducted in seven rehabilitation centres. Hemiplegic patients were recruited after unilateral stroke lasting less than six months. Exclusion criteria were: impossibility to stand for 10 seconds; ankle passive dorsiflexion <5 degrees with knee flexed to 90 degrees; triceps spasticity ≥3/4 on the Ashworth modified scale; diseases that might impair active participation in the study. Thirteen patients were randomized to the Chignon group and 15 to the control group. Included patients were given a standard ankle-foot orthosis or Chignon ankle-foot orthosis. The Chignon ankle-foot orthosis is an articulated double-stopped custom-made orthosis with elements to assist dorsiflexion and plantar flexion. Gait speed improvement (ten-metre test), kinematic assessment, and functional scales were assessed.

Results: Gain ratio of walking speed with the orthosis increased significantly more in the Chignon group than in the control group at day 0 (27.2  ±  36% versus −0.8  ±  17%; P = 0.006), day 30 (39.9  ±  19% versus 7.5  ±  17%; P = 0.0004) and day 90 (44.6  ±  27% versus 17.1  ±  0.3%; P = 0.04). There was also a significant improvement in kinematic parameters and spasticity in the Chignon group.

Conclusion: Early compensation of distal motor deficiency by the Chignon ankle-foot orthosis improves the immediate gait of hemiplegics more than the standard ankle-foot orthosis and seems to modify motor recovery processes in the legs after stroke.

Effects of an ankle-foot orthosis with oil damper on muscle activity in adults after stroke

BACKGROUND AND OBJECTIVE

An ankle-foot orthosis with an oil damper (AFO-OD) was developed to resist plantarflexion motion, thereby improving hemiplegic gait performance. The purpose of this study was to determine the effect of AFO-OD on muscle activity during the gait cycle in individuals affected by stroke.

METHODS

Electromyography (EMG) was used to assess gait at a self-selected speed while wearing an AFO-OD or an AFO with a plantarflexion stop (AFO-PS) worn on the affected side in 11 stroke survivors and on the right side in 11 age-matched healthy adults. EMG signals were obtained from the tibialis anterior (TA), gastrocnemius (GAS), and soleus (SOL) muscles. In addition, the ankle joint angle under both braces and the plantarflexion resistance torque (PFRT) under AFO-OD were monitored.

RESULTS

Peak PFRT under AFO-OD was observed during the loading response phase (LRP) in both groups. AFO-OD promoted adequate plantarflexion during LRP in the stroke group, whereas AFO-PS did not. Compared with the AFO-PS, the AFO-OD significantly reduced GAS EMG amplitude during LRP in the stroke group, which was significantly correlated with peak PFRT during LRP.

CONCLUSION

AFO-OD assisted the "heel rocker function" and reduced GAS muscle EMG amplitude during LRP.

Gait improvement of hemiplegic patients using an ankle-foot orthosis with assistance of heel rocker function

The ankle-foot orthosis (AFO) with oil damper, GaitSolution (GS), was previously developed to make heel rocker function possible during the gait of hemiplegic patients. To clarify the characteristics of patients who show adaptation to GS use, a questionnaire was completed by the clinicians responsible for 99 patients with hemiplegia who participated in this study. Clinicians completed items concerning gait data of patients without AFO use and with GS use, adaptation to the use of GS, and patient opinion of GS use. Approximately 60% of patients achieved heel rocker function during the loading response of the paretic limb and improved gait when using GS. A comparison of the patients whose gaits were improved by GS more than by other AFOs revealed the use of GS was well suited to the gait of patients with a relatively higher Brunnstrom stage and a slightly flexed knee joint during the stance phase. Approximately 60% of patients reported feeling comfortable using GS, although patient comfort did not necessarily coincide with the results of gait assessment by clinicians. Patient comfort mainly depended on trunk posture and hip joint outward rotation; hip joint outward rotation could be improved using GS in the recovery phase but not in the maintenance phase. This result implies the importance of gait training in the early stage of rehabilitation.

A pneumatic power harvesting ankle-foot orthosis to prevent foot-drop

Background

A self-contained, self-controlled, pneumatic power harvesting ankle-foot orthosis (PhAFO) to manage foot-drop was developed and tested. Foot-drop is due to a disruption of the motor control pathway and may occur in numerous pathologies such as stroke, spinal cord injury, multiple sclerosis, and cerebral palsy. The objectives for the prototype PhAFO are to provide toe clearance during swing, permit free ankle motion during stance, and harvest the needed power with an underfoot bellow pump pressurized during the stance phase of walking.

Methods

The PhAFO was constructed from a two-part (tibia and foot) carbon composite structure with an articulating ankle joint. Ankle motion control was accomplished through a cam-follower locking mechanism actuated via a pneumatic circuit connected to the bellow pump and embedded in the foam sole. Biomechanical performance of the prototype orthosis was assessed during multiple trials of treadmill walking of an able-bodied control subject (n = 1). Motion capture and pressure measurements were used to investigate the effect of the PhAFO on lower limb joint behavior and the capacity of the bellow pump to repeatedly generate the required pneumatic pressure for toe clearance.

Results

Toe clearance during swing was successfully achieved during all trials; average clearance 44 ± 5 mm. Free ankle motion was observed during stance and plantarflexion was blocked during swing. In addition, the bellow component repeatedly generated an average of 169 kPa per step of pressure during ten minutes of walking.

Conclusion

This study demonstrated that fluid power could be harvested with a pneumatic circuit built into an AFO, and used to operate an actuated cam-lock mechanism that controls ankle-foot motion at specific periods of the gait cycle.

Effect of ankle-foot orthosis alignment and foot-plate length on the gait of adults with poststroke hemiplegia

OBJECTIVE

To investigate the effect of ankle-foot orthosis (AFO) alignment and foot-plate length on sagittal plane knee kinematics and kinetics during gait in adults with poststroke hemiplegia.

DESIGN

Repeated measures, quasi-experimental study.

SETTING

Motion analysis laboratory.

PARTICIPANTS

Volunteer sample of adults with poststroke hemiplegia (n=16) and able-bodied adults (n=12) of similar age.

INTERVENTIONS

Subjects with hemiplegia were measured walking with standardized footwear in 4 conditions: (1) no AFO (shoes only); (2) articulated AFO with 90 degrees plantar flexion stop and full-length foot-plate-conventionally aligned AFO (CAFO); (3) the same AFO realigned with the tibia vertical in the shoe-heel-height compensated AFO (HHCAFO); and (4) the same AFO (tibia vertical) with 3/4 length foot-plate-3/4 AFO. Gait of able-bodied control subjects was measured on a single occasion to provide a normal reference.

MAIN OUTCOME MEASURES

Sagittal plane ankle and knee kinematics and kinetics.

RESULTS

In adults with hemiplegia, walking speed was unaffected by the different conditions (P=.095). Compared with the no AFO condition, all AFOs decreased plantar flexion at initial contact and mid-swing (P<.001) and changed the peak knee moment in early stance from flexor to extensor (P<.000). Both AFOs with full-length foot-plates significantly increased the peak stance phase plantar flexor moment compared with no AFO and resulted in a peak knee extensor moment in early stance that was significantly greater than control subjects, whereas the AFO with three-quarter length foot-plate resulted in ankle dorsiflexion during stance and swing that was significantly less than control subjects.

CONCLUSIONS

These findings suggest that when an articulated AFO is to be used, a full-length foot-plate in conjunction with a plantar flexion stop may be considered to improve early stance knee moments for people with poststroke hemiplegia.