A Novel Gait Event Detection Algorithm Using a Thigh-Worn Inertial Measurement Unit and Joint Angle Information.

This paper describes the development and evaluation of a novel, threshold-based gait event detection algorithm utilizing only one thigh inertial measurement unit (IMU) and unilateral, sagittal plane hip and knee joint angles. The algorithm was designed to detect heel strike (HS) and toe off (TO) gait events, with the eventual goal of detection in a real-time exoskeletal control system. The data used in the development and evaluation of the algorithm were obtained from two gait databases, each containing synchronized IMU and ground reaction force (GRF) data. All database subjects were healthy individuals walking in either a level-ground, urban environment or a treadmill lab environment. Inertial measurements used were three-dimensional thigh accelerations and three-dimensional thigh angular velocities. Parameters for the TO algorithm were identified on a per-subject basis. The GRF data were utilized to validate the algorithm's timing accuracy and quantify the fidelity of the algorithm, measured by the F1-Score. Across all participants, the algorithm reported a mean timing error of -41±20 ms with an F1-Score of 0.988 for HS. For TO, the algorithm reported a mean timing error of -1.4±21 ms with an F1-Score of 0.991. The results of this evaluation suggest that this algorithm is a promising solution to inertial based gait event detection; however, further refinement and real-time evaluation are required for use in exoskeletal control.

Impact-Aware Foot Motion Reconstruction and Ramp/Stair Detection Using One Foot-Mounted Inertial Measurement Unit.

Motion reconstruction using wearable sensors enables broad opportunities for gait analysis outside laboratory environments. Inertial Measurement Unit (IMU)-based foot trajectory reconstruction is an essential component of estimating the foot motion and user position required for any related biomechanics metrics. However, limitations remain in the reconstruction quality due to well-known sensor noise and drift issues, and in some cases, limited sensor bandwidth and range. In this work, to reduce drift in the height direction and handle the impulsive velocity error at heel strike, we enhanced the integration reconstruction with a novel kinematic model that partitions integration velocity errors into estimates of acceleration bias and heel strike vertical velocity error. Using this model, we achieve reduced height drift in reconstruction and simultaneously accomplish reliable terrain determination among level ground, ramps, and stairs. The reconstruction performance of the proposed method is compared against the widely used Error State Kalman Filter-based Pedestrian Dead Reckoning and integration-based foot-IMU motion reconstruction method with 15 trials from six subjects, including one prosthesis user. The mean height errors per stride are 0.03±0.08 cm on level ground, 0.95±0.37 cm on ramps, and 1.27±1.22 cm on stairs. The proposed method can determine the terrain types accurately by thresholding on the model output and demonstrates great reconstruction improvement in level-ground walking and moderate improvement on ramps and stairs.

Unsupervised Gait Event Identification with a Single Wearable Accelerometer and/or Gyroscope: A Comparison of Methods across Running Speeds, Surfaces, and Foot Strike Patterns.

We evaluated 18 methods capable of identifying initial contact (IC) and terminal contact (TC) gait events during human running using data from a single wearable sensor on the shank or sacrum. We adapted or created code to automatically execute each method, then applied it to identify gait events from 74 runners across different foot strike angles, surfaces, and speeds. To quantify error, estimated gait events were compared to ground truth events from a time-synchronized force plate. Based on our findings, to identify gait events with a wearable on the shank, we recommend the Purcell or Fadillioglu method for IC (biases +17.4 and -24.3 ms; LOAs -96.8 to +131.6 and -137.0 to +88.4 ms) and the Purcell method for TC (bias +3.5 ms; LOAs -143.9 to +150.9 ms). To identify gait events with a wearable on the sacrum, we recommend the Auvinet or Reenalda method for IC (biases -30.4 and +29.0 ms; LOAs -149.2 to +88.5 and -83.3 to +141.3 ms) and the Auvinet method for TC (bias -2.8 ms; LOAs -152.7 to +147.2 ms). Finally, to identify the foot in contact with the ground when using a wearable on the sacrum, we recommend the Lee method (81.9% accuracy).

Combination of optimized tissue engineering bone implantation with heel-strike like mechanical loading to repair segmental bone defect in New Zealand rabbits.

In this study, effects of combining optimized tissue engineering bone (TEB) implantation with heel-strike like mechanical loading to repair segmental bone defect in New Zealand rabbits were investigated. Physiological characteristics of bone marrow mesenchymal stem cells (BMMSCs), compact bone cells (CBCs), and bone marrow and compact bone coculture cells (BMMSC-CBCs) were compared to select the optimal seed cells for optimized TEB construction. Rabbits with segmental bone defects were treated in different ways (cancellous bone scaffold for group A, cancellous bone scaffold and mechanical loading for group B, optimized TEB for group C, optimized TEB and mechanical loading for group D, n = 4), and the bone repair were compared. BMMSC-CBCs showed better proliferation capacity than CBCs (p < 0.01) and stronger osteogenic differentiation ability than BMMSCs (p < 0.05). Heel-strike like mechanical loading improved proliferation and osteogenic differentiation ability and expression levels of TGFß1 as well as BMP2 of seed cells in vitro (p < 0.05). At week 12 post-operation, group D showed the best bone repair, followed by groups B and C, while group A finished last (p < 0.05). During week 4 to 12 post-operation, group D peaked in terms of expression levels of TGFß1, BMP2, and OCN, followed by groups B and C, while group A finished last (p < 0.05). Thus, BMMSC-CBCs showed good proliferation and osteogenic differentiation ability, and they were thought to be better as seed cells than BMMSCs and CBCs. The optimized TEB implantation combined with heel-strike like mechanical loading had a synergistic effect on bone defect healing, and enhanced expression of TGFß1 and BMP2 played an important role in this process.

Soft tissue deformations explain most of the mechanical work variations of human walking.

Humans perform mechanical work during walking, some by leg joints actuated by muscles, and some by passive, dissipative soft tissues. Dissipative losses must be restored by active muscle work, potentially in amounts sufficient to cost substantial metabolic energy. The most dissipative, and therefore costly, walking conditions might be predictable from the pendulum-like dynamics of the legs. If this behavior is systematic, it may also predict the work distribution between active joints and passive soft tissues. We therefore tested whether the overall negative work of walking, and the fraction owing to soft tissue dissipation, are both predictable by a simple dynamic walking model across a wide range of conditions. The model predicts whole-body negative work from the leading leg's impact with the ground (termed the collision), to increase with the squared product of walking speed and step length. We experimentally tested this in humans (N=9) walking in 26 different combinations of speed (0.7-2.0 m s-1) and step length (0.5-1.1 m), with recorded motions and ground reaction forces. Whole-body negative collision work increased as predicted (R2=0.73), with a consistent fraction of approximately 63% (R2=0.88) owing to soft tissues. Soft tissue dissipation consistently accounted for approximately 56% of the variation in total whole-body negative work, across a wide range of speed and step length combinations. During typical walking, active work to restore dissipative losses could account for 31% of the net metabolic cost. Soft tissue dissipation, not included in most biomechanical studies, explains most of the variation in negative work of walking, and could account for a substantial fraction of the metabolic cost.

Effect of Heel-First Strike Gait on Knee and Ankle Mechanics.

Background and Objectives: Acquiring knowledge about the magnitude and direction of induced joint forces during modifying gait strategies is critical for proper exercise prescription. The present study aimed to evaluate whether a heel-first strike pattern during gait can affect the biomechanical characteristics of ankle and knee joints among asymptomatic people. Materials and Methods: In this cross-sectional study performed in the biomechanics laboratory, 13 professional healthy male athletes walked on an instrumented walkway under two walking conditions. For the normal condition, subjects were instructed to walk as they normally would. For the heel-first strike condition, subjects were instructed to walk with heel-first strike pattern and increase heel contact duration as much as possible. Then, knee and ankle joint range of motions and moments, as well as vertical ground reaction force was measured by the Kistler force plate and Vicon motion analysis system. Results: Knee flexion angle at the initial contact and during stance phase was significantly lower when increasing the heel strike pattern. In addition, the mean values of the knee external rotation and adductor moments during heel strike condition were lower than those in normal walking. Further, the ankle dorsiflexion range of motion (ROM) during mid-stance increased significantly during heel-first strike pattern compared to the value in normal gait pattern. Conclusions: The modification of gait pattern including heel-first strike pattern can reduce the mechanical load applied to the knee, while improving the extensibility of gastro-soleus muscle complex.

Mechanics of heel-strike plantigrady in African apes.

The initiation of a walking step with a heel strike is a defining characteristic of humans and great apes but is rarely found in other mammals. Despite the considerable importance of heel strike to an understanding of human locomotor evolution, no one has explicitly tested the fundamental mechanical question of why great apes use a heel strike. In this report, we test two hypotheses (1) that heel strike is a function of hip protraction and/or knee extension and (2) that short-legged apes with a midfoot that dorsiflexes at heel lift and long digits for whom digitigrady is not an option use heel-strike plantigrady. This strategy increases hip translation while potentially moderating the cost of redirecting the center of mass ('collisional costs') during stance via rollover along the full foot from the heel to toes. We quantified hind limb kinematics and relative hip translation in ten species of primates, including lemurs, terrestrial and arboreal monkeys, chimpanzees, and gorillas. Chimpanzees and gorillas walked with relatively extended knees but only with moderately protracted hips or hind limbs, partially rejecting the first hypothesis. Nonetheless, chimpanzees attained relative hip translations comparable with those of digitigrade primates. Heel-strike plantigrady may be a natural result of a need for increased hip translations when forelimbs are relatively long and digitigrady is morphologically restricted. In addition, foot rollover from the heel to toe in large, short-legged apes may reduce energetic costs of redirecting the center of mass at the step-to-step transition as it appears to do in humans. Heel strike appears to have been an important mechanism for increasing hip translation, and possibly reducing energetic costs, in early hominins and was fundamental to the evolution of the modern human foot and human bipedalism.

Lower extremity joint loads in habitual rearfoot and mid/forefoot strike runners with normal and shortened stride lengths.

Our purpose was to compare joint loads between habitual rearfoot (hRF) and habitual mid/forefoot strikers (hFF), rearfoot (RFS) and mid/forefoot strike (FFS) patterns, and shorter stride lengths (SLs). Thirty-eight hRF and hFF ran at their normal SL, 5% and 10% shorter, as well as with the opposite foot strike. Three-dimensional ankle, knee, patellofemoral (PF) and hip contact forces were calculated. Nearly all contact forces decreased with a shorter SL (1.2-14.9% relative to preferred SL). In general, hRF had higher PF (hRF-RFS: 10.8 ± 1.4, hFF-FFS: 9.9 ± 2.0 BWs) and hip loads (axial hRF-RFS: -9.9 ± 0.9, hFF-FFS: -9.6 ± 1.0 BWs) than hFF. Many loads were similar between foot strike styles for the two groups, including axial and lateral hip, PF, posterior knee and shear ankle contact forces. Lateral knee and posterior hip contact forces were greater for RFS, and axial ankle and knee contact forces were greater for FFS. The tibia may be under greater loading with a FFS because of these greater axial forces. Summarising, a particular foot strike style does not universally decrease joint contact forces. However, shortening one's SL 10% decreased nearly all lower extremity contact forces, so it may hold potential to decrease overuse injuries associated with excessive joint loads.

Combination of Heel-strike like Mechanical Loading with Deproteinized Cancellous Bone Scaffold Implantation to Repair Segmental Bone Defects in Rabbits.

Under physiological conditions bone defects often occur at mechanical load bearing sites and bone substitutes used for regeneration should be similarly subjected to mechanical loading stress. In this study, we investigated whether a novel heel-strike like mechanical loading method can be used as a complementary therapy to promote bone regeneration following bone substitute grafting. To test this, three groups of rabbits with segmental bone defects in the tibia were implanted with bovine deproteinized cancellous bone scaffold (DCBS), with one group also receiving heel-strike like mechanical loading generated by a rap stress stimulator. From weeks 4-12 post-operation X-ray and micro-CT scanning showed that rabbits receiving combination therapy had significantly more callus at the bone defect. Moreover, bone defects in the combination group were completely replaced with new bone at week 12, while the DCBS implantation alone group healed only partially and rabbits receiving neither DCBS nor mechanical loading developed only small calluses throughout the observation period. Analysis of micro-CT scanning results demonstrated that new bone density in the combination group was significantly higher than the DCBS only group at weeks 4 and 12 (p<0.05). H&E staining results also indicated a significantly higher percentage of new bone in the bone defect area and a lower percentage of residual scaffold in the combination group compared to the DCBS only group (p<0.05). Thus, this heel-strike like mechanical loading method appears to accelerate bone regeneration following substitute implantation by restoring a local mechanical loading environment in segmental bone defects.

Effects of Neuromuscular Training on the Rear-foot Angle Kinematics in Elite Women Field Hockey Players with Chronic Ankle Instability.

The aims of this study were to investigate the ankle position, the changes and persistence of ankle kinematics after neuromuscular training in athletes with chronic ankle instability (CAI). A total of 21 national women's field hockey players participated (CAI = 12, control = 9). Ankle position at heel strike (HS), midstance (MS), and toe touch (TT) in the frontal plane during walking, running and landing were measured using 3D motion analysis. A 6-week neuromuscular training program was undertaken by the CAI group. Measurements of kinematic data for both groups were measured at baseline and the changes in kinematic data for CAI group were measured at 6 and 24 weeks. The kinematic data at HS during walking and running demonstrated that the magnitude of the eversion in the CAI group (-5.00° and -4.21°) was less than in the control group (-13.45°and -9.62°). The kinematic data at MS also exhibited less ankle eversion in the CAI group (-9.36° and -8.18°) than in the control group (-18.52° and -15.88°). Ankle positions at TT during landing were comparable between groups. Following the 6-week training, the CAI participants demonstrated a less everted ankle at HS during walking and running (-1.77° and -1.76°) compared to the previous positions. They also showed less ankle eversion at MS (-5.14° and -4.19°). Ankle orientation at TT changed significantly to an inverted ankle position (from -0.26° to 4.11°). The ankle kinematics were restored back to the previous positions at 24 weeks except for landing. It appeared that athletes with unstable ankle had a relatively inverted ankle position, and that 6-week neuromuscular training had an immediate effect on changing ankle orientation toward a less everted direction. The changed ankle kinematics seemed to persist during landing but not during walking and running.

The role of plantigrady and heel-strike in the mechanics and energetics of human walking with implications for the evolution of the human foot.

Human bipedal locomotion is characterized by a habitual heel-strike (HS) plantigrade gait, yet the significance of walking foot-posture is not well understood. To date, researchers have not fully investigated the costs of non-heel-strike (NHS) walking. Therefore, we examined walking speed, walk-to-run transition speed, estimated locomotor costs (lower limb muscle volume activated during walking), impact transient (rapid increase in ground force at touchdown) and effective limb length (ELL) in subjects (n=14) who walked at self-selected speeds using HS and NHS gaits. HS walking increases ELL compared with NHS walking since the center of pressure translates anteriorly from heel touchdown to toe-off. NHS gaits led to decreased absolute walking speeds (P=0.012) and walk-to-run transition speeds (P=0.0025), and increased estimated locomotor energy costs (P<0.0001) compared with HS gaits. These differences lost significance after using the dynamic similarity hypothesis to account for the effects of foot landing posture on ELL. Thus, reduced locomotor costs and increased maximum walking speeds in HS gaits are linked to the increased ELL compared with NHS gaits. However, HS walking significantly increases impact transient values at all speeds (P<0.0001). These trade-offs may be key to understanding the functional benefits of HS walking. Given the current debate over the locomotor mechanics of early hominins and the range of foot landing postures used by nonhuman apes, we suggest the consistent use of HS gaits provides key locomotor advantages to striding bipeds and may have appeared early in hominin evolution.

A vision based proposal for classification of normal and abnormal gait using RGB camera.

Human gait is mainly related to the foot and leg movements but, obviously, the entire motor system of the human body is involved. We hypothesise that movement parameters such as dynamic balance, movement harmony of each body element (arms, head, thorax…) could enable us to finely characterise gait singularities to pinpoint potential diseases or abnormalities in advance. Since this paper deals with the preliminary problem pertaining to the classification of normal and abnormal gait, our study will revolve around the lower part of the body. Our proposal presents a functional specification of gait in which only observational kinematic aspects are discussed. The resultant specification will confidently be open enough to be applied to a variety of gait analysis problems encountered in areas connected to rehabilitation, sports, children's motor skills, and so on. To carry out our functional specification, we develop an extraction system through which we analyse image sequences to identify gait features. Our prototype not only readily lets us determine the dynamic parameters (heel strike, toe off, stride length and time) and some skeleton joints but also satisfactorily supplies us with a proper distinction between normal and abnormal gait. We have performed experiments on a dataset of 30 samples.

Estimation of Temporal Gait Events from a Single Accelerometer Through the Scale-Space Filtering Idea.

The purpose of this paper is to develop an accelerometry system capable of performing gait event demarcation and calculation of temporal parameters using a single waist-mounted device. Particularly, a mobile phone positioned over the L2 vertebra is used to acquire trunk accelerations during walking. Signals from the acceleration magnitude and the vertical acceleration are smoothed through different filters. Cut-off points between filtered signals as a result of convolving with varying levels of Gaussian filters and other robust features against temporal variation and noise are used to identify peaks that correspond to gait events. Five pre-frail older adults and five young healthy adults were recruited in an experiment. Cadence, step/stride time, step/stride CV, step asymmetry and percentages of the stance/swing and single/double support phases, among the two groups of different mobility were quantified by the system.

End-stage ankle arthritis alters dynamic stability during gait as measured by margin of stability between limbs and compared to healthy controls.

OBJECTIVE: This study aimed to assess dynamic stability in individuals with end-stage ankle arthritis compared to healthy controls by evaluating the margin of stability (MoS) during gait. DESIGN: A cohort of 50 participants with end-stage ankle arthritis (AA) and 50 matched healthy controls (HC) were analyzed from an IRB approved database. Kinematic data were collected using an eight-camera motion analysis system, and MoS was calculated based on the extrapolated center of mass (XCoM) and the base of support (BoS). Statistical analysis was performed using a linear mixed effects model with gait speed as a covariate. RESULTS: The analysis revealed a significant interaction between the group (AA vs. HC) and limb (arthritic vs. non-arthritic) at heel-strike and midstance. The non-arthritic limb demonstrated a significantly smaller AP MoS during heel-strike compared to the arthritic limb and either of the limbs of the HC group (p < 0.001). The arthritic limb demonstrated a significantly greater ML MoS during midstance compared to the non-arthritic limb and either of the limbs of the HC group (p < 0.001). AA group had significant slower gait speed (p < 0.001), smaller step length (p = 0.015) and smaller locomotor rehabilitation index (p < 0.001) than HC. CONCLUSION: Individuals with end-stage ankle arthritis exhibit altered dynamic stability during gait, with a significantly smaller AP MoS on the non-arthritic limb at heel-strike and greater ML MoS on the arthritic limb at midstance compared to healthy controls. Our results suggest that individuals with ankle arthritis are less stable when navigating single limb support of the arthritic limb. Further research should further examine the associations with fall risk in patients with ankle arthritis and evaluate the effectiveness of therapeutic interventions targeting these factors.

The relative size of the calcaneal tuber reflects heel strike plantigrady in African apes and humans.

OBJECTIVES: The positional repertoire of the human-chimpanzee last common ancestor is critical for reconstructing the evolution of bipedalism. African apes and humans share a heel strike plantigrade foot posture associated with terrestriality. Previous research has established that modern humans have a relatively large and intrinsically robust calcaneal tuber equipped to withstand heel strike forces associated with bipedal walking and running. However, it is unclear whether African apes have a relatively larger calcaneal tuber than non-heel-striking primates, and how this trait might have evolved among anthropoids. Here, I test the hypothesis that heel-striking primates have a relatively larger calcaneal tuber than non-heel-striking primates. METHODS: The comparative sample includes 331 individuals and 53 taxa representing hominoids, cercopithecoids, and platyrrhines. Evolutionary modeling was used to test for the effect of foot posture on the relative size of the calcaneal tuber in a phylogenetic framework that accounts for adaptation and inertia. Bayesian evolutionary modeling was used to identify selective regime shifts in the relative size of the calcaneal tuber among anthropoids. RESULTS: The best fitting evolutionary model was a Brownian motion model with regime-dependent trends characterized by relatively large calcaneal tubers among African apes and humans. Evolutionary modeling provided support for an evolutionary shift toward a larger calcaneal tuber at the base of the African ape and human clade. CONCLUSIONS: The results of this study support the view that African apes and humans share derived traits related to heel strike plantigrady, which implies that humans evolved from a semi-terrestrial quadrupedal ancestor.

Does the Heel's Dissipative Energetic Behavior Affect Its Thermodynamic Responses During Walking?

Most of the terrestrial legged locomotion gaits, like human walking, necessitate energy dissipation upon ground collision. In humans, the heel mostly performs net-negative work during collisions, and it is currently unclear how it dissipates that energy. Based on the laws of thermodynamics, one possibility is that the net-negative collision work may be dissipated as heat. If supported, such a finding would inform the thermoregulation capacity of human feet, which may have implications for understanding foot complications and tissue damage. Here, we examined the correlation between energy dissipation and thermal responses by experimentally increasing the heel's collisional forces. Twenty healthy young adults walked overground on force plates and for 10 min on a treadmill (both at 1.25 ms-1) while wearing a vest with three different levels of added mass (+0%, +15%, & +30% of their body mass). We estimated the heel's work using a unified deformable segment analysis during overground walking. We measured the heel's temperature immediately before and after each treadmill trial. We hypothesized that the heel's temperature and net-negative work would increase when walking with added mass, and the temperature change is correlated with the increased net-negative work. We found that walking with +30% added mass significantly increased the heel's temperature change by 0.72 ± 1.91   ℃ (p = 0.009) and the magnitude of net-negative work (extrapolated to 10 min of walking) by 326.94 ± 379.92 J (p = 0.005). However, we found no correlation between the heel's net-negative work and temperature changes (p = 0.277). While this result refuted our second hypothesis, our findings likely demonstrate the heel's dynamic thermoregulatory capacity. If all the negative work were dissipated as heat, we would expect excessive skin temperature elevation during prolonged walking, which may cause skin complications. Therefore, our results likely indicate that various heat dissipation mechanisms control the heel's thermodynamic responses, which may protect the health and integrity of the surrounding tissue. Also, our results indicate that additional mechanical factors, besides energy dissipation, explain the heel's temperature rise. Therefore, future experiments may explore alternative factors affecting thermodynamic responses, including mechanical (e.g., sound & shear-stress) and physiological mechanisms (e.g., sweating, local metabolic rate, & blood flow).

Foot-floor contact pattern in children and adults with Dravet Syndrome.

BACKGROUND: Dravet Syndrome (DS) is a developmental and epileptic encephalopathy characterized by severe drug-resistant seizures and associated with cognitive and motor impairments. Walking problems are frequently observed. As the foot plays a key role during walking, compromised foot function can be a feature of deviant gait. AIM: To investigate foot function in DS by characterizing foot-floor contact patterns using pedobarography. METHODS: A total of 31 children and adults were included in the DS group (aged 5.2-32.8 years, 17 female, 174 steps) and 30 in the control group (aged 6.0-32.9, 16 female, 180 steps). The foot-floor contact pattern was evaluated based on progression, length and smoothness (spectral arc length) of the center of pressure (CoP). Linear mixed models were used to identify differences between non-heel strikes and heel strikes and between the DS and control group. RESULTS: Fifteen participants with DS showed inconsistency in the type of foot-floor contact (heel strikes and non-heel strikes). Heel strikes of participants with DS had significantly reduced time of CoP under the hindfoot and increased time under the midfoot region compared to the control group. Significant time and age effects were detected. CONCLUSIONS AND IMPLICATIONS: Deviant foot-floor contact patterns were observed in DS. Possible gait immaturity and instability as well as implications for interventions are discussed.

Efficacy of dance-based paradigms, wearable sensors, and auditory feedback for gait retraining in children: A feasibility study.

BACKGROUND: Different feedback modes such as auditory, visual and haptic have been used in the past for gait retraining or learning movement patterns. The primary goal of this study was to investigate whether real time auditory feedback would be effective in children learning novel, dance-based movement patterns. For this purpose, a prototype wearable sensor was developed to provide auditory feedback whenever a child touches their heel to the ground. METHODS: To test the effectiveness of the auditory feedback in learning new patterns, typically developing children were taught simple Indian dance protocols consisting of four counts of foot-work which involved alternating heel-toe movements. The effect of wearing the sensor was assessed by the maximum vertical force with which the subjects struck their foot on the plate. RESULTS: Auditory feedback reduced the learning time and increased the number of correct movement patterns for trial duration of 2 min. The prototype device did not alter the maximum force with which the subject placed the foot on the ground. CONCLUSIONS: Real time auditory feedback can be reliably used to learn novel movement patterns.

An Adaptable Human-Like Gait Pattern Generator Derived From a Lower Limb Exoskeleton.

Walking rehabilitation processes include many repetitions of the same physical movements in order to replicate, as close as possible, the normal gait trajectories, and kinematics of all leg joints. In these conventional therapies, the therapist's ability to discover patient's limitations-and gradually reduce them-is key to the success of the therapy. Lower-limb robotic exoskeletons have strong deficiencies in this respect as compared to an experienced therapist. Most of the currently available robotic solutions are not able to properly adapt their trajectories to the biomechanical limitations of the patient. With this in mind, much research and development is still required in order to improve artificial human-like walking patterns sufficiently for valuable clinical use. The work herein reported develops and presents a method to acquire and saliently analyze subject-specific gait data while the subject dons a passive lower-limb exoskeleton. Furthermore, the method can generate adjustable, yet subject-specific, kinematic gait trajectories useful in programming controllers for future robotic rehabilitation protocols. A human-user study with ten healthy subjects provides the experimental setup to validate the proposed method. The experimental protocol consists in capturing kinematic data while subjects walk, with the donned H2 lower-limb exoskeleton, across three experimental conditions: walking with three different pre-determined step lengths marked on a lane. The captured ankle trajectories in the sagittal plane were found by normalizing all trials of each test from one heel strike to the next heel strike independent of the specific gait features of each individual. Prior literature suggests analyzing gait in phases. A preliminary data analysis, however, suggests that there exist six key events of the gait cycle, events that can adequately characterize gait for the purposes required of robotic rehabilitation including gait analysis and reference trajectory generation. Defining the ankle as an end effector and the hip as the origin of the coordinate frame and basing the linear regression calculations only on the six key events, i.e., Heel Strike, Toe Off, Pre-Swing, Initial Swing, Mid-Swing, and Terminal Swing, it is possible to generate a new calculated ankle trajectory with an arbitrary step length. The Leave-One-Out Cross Validation algorithm was used to estimate the fitting error of the calculated trajectory vs. the characteristic captured trajectory per subject, showing a fidelity average value of 95.2, 96.1, and 97.2%, respectively, for each step-length trial including all subjects. This research presents method to capture ankle trajectories from subjects and generate human-like ankle trajectories that could be scaled and computed on-line, could be adjusted to different gait scenarios, and could be used not only to generate reference trajectories for gait controllers, but also as an accurate and salient benchmark to test the human likeness of gait trajectories employed by existing robotic exoskeletal devices.

Choosing the target wisely: partial tibial nerve transfer to extensor digitorum motor branches with simultaneous posterior tibial tendon transfer. Could this be a way to improve functional outcome and gait biomechanics?

OBJECTIVE: The objective of this study was clinical assessment of the reduction of pathological motor phenomena with the recovery of long toe extensors, and evaluation of functional outcome with simultaneous nerve and tendon transfer in cases of common peroneal nerve (CPN) injuries. METHODS: Seven male patients (mean age 26.4 years) received a partial tibial nerve transfer to the extensor hallucis longus muscle (MEHL) and extensor digitorum longus muscle (MEDL) motor branches, after a mean of 2.7 months following a traction-type injury to the CPN. Tibialis posterior muscle (MTP) tendon transfer through the interosseous route was performed on the same day. The follow-up period included a clinical neurological examination, a modified Stanmore System questionnaire (MSSQ), electromyographic examination of the interference pattern, and a video-based analysis of the gait biomechanics in the 3rd and 12th months. Video analysis of the gait investigated the presence or reduction of "stair-climbing maneuver" (SCM), foot slap (FS), and foot stability during the gait cycle. RESULTS: The average range of active dorsiflexion in the 3rd month was 0.85°. SCM accompanied walking in 6 patients (86%). FS accompanied walking in 3 patients (43%) and 3 patients (43%) avoided FS by planting the entire foot on the ground. All patients required orthopedic support (shoe inserts) to compensate for mediolateral foot instability. The average MSSQ score was 80.4 points. The average duration for the effective recovery of function (≥ 4 points on the Medical Research Council grading system) of long toe extensors was 11.2 months. The average range of active dorsiflexion in the 12th month increased to 4.4°. A reduction of FS was observed in 5 patients (71%). Excessive foot eversion was reduced in 4 patients (57%). Another 3 patients (43%) required no specific orthopedic shoe inserts. Reduction of pathological motor phenomena with recovery of the long toe extensors resulted in an increase of functional outcome. The average MSSQ score after 12 months was 92.4 points. CONCLUSIONS: Partial tibial nerve transfer to the motor branches of the extensor hallucis longus and the long toe extensors along with the simultaneous tibialis posterior tendon transfer produce the reduction of FS and bring mediolateral stability to the foot, i.e., improved gait biomechanics. The reduction of pathological motor phenomena at the time of recovery of the long toe extensors is reflected in an increase in patients' functional perception of the injured lower extremity during daily walking.