The effects of walking speed on minimum toe clearance and on the temporal relationship between minimum clearance and peak swing-foot velocity in unilateral trans-tibial amputees

An exploration of the agreement, inter- and intra-rater reliability, and reproducibility of three common methods used to measure minimum toe clearance with optical motion capture systems under three shoe conditions

BACKGROUND

The gait variable minimum toe clearance (MTC) has been investigated concerning trip-related fall research in older adults. However, comparing studies is difficult due to the different methods used to measure MTC and shoe conditions, which may affect agreement. Measurement methods can include using a single virtual point (SVP), multiple virtual points (MVPS), or metatarsal head markers (marker-based). The shoe types used in MTC studies include standard shoes (SS), personal shoes (PS), and barefoot (BF) conditions.

RESEARCH QUESTION

What is the agreement, inter and intra-rater reliability, and repeatability for the 3 commonly used methods of measuring MTC (SVP, MVPS, marker-based) under the 3 shoe conditions for optical motion capture systems (SS, PS, BF)?

METHODS

Twelve healthy young adults (mean [SD] 23.8 [1.9] years,7 males) participated in this observational study. In a randomized order, participants completed 25 walking trials at self-selected normal and slow speeds in SS, PS, and BF conditions while infrared cameras recorded the maker trajectories. Each participant performed a familiarization trial for at least 1 minute before collecting data on each shoe condition. Statistical analyses included Bland-Altman 95 % limits of agreement (LOA) analyses, interclass correlation coefficient (ICC) analyses for inter- and intra-rater reliability, and the repeatability coefficient (RC).

RESULTS

The SVP and MVPS had a tighter 95 % LOA than the marker-based method, particularly under SS and BF conditions. The inter-rater reliability was good to excellent under these shoe conditions. Intra-reliability for all methods under all shoe conditions was excellent (ICC >.90). The RC was very similar for each method, with none exceeding 1.02 cm.

SIGNIFICANCE

The study provides estimates of the agreement between MTC methods and suggests that only SVP or MVPS produced similar results in SS/BF conditions. Additionally, a "true" change in MTC requires a difference greater than 1.02 cm.

Investigating the Effects of a Kinematic Gait Parameter-Based Haptic Cue on Toe Clearance in Parkinson's Patients

Recurrent falls pose a significant challenge for Parkinson's disease (PD) patients and are a leading cause of disability in this population. One contributing factor to these recurring falls is the reduced minimum toe clearance (mTC). Preventing such falls by enhancing mTC has become an important goal in gait training among PD patients. In this paper, we propose a wearable cueing-based novel gait training device in anticipation of improved mTC. The cueing device records the foot strike angle (FSA) and cues the participants if the FSA is observed above a threshold. The patients with PD (n = 8) were recruited and asked to walk under two conditions: (a) with cue and (b) without cue at a self-selected speed during the ON medication state. Kinetic and kinematic gait parameters such as vertical ground reaction force, center of pressure, toe clearance, and FSA were recorded. A Mann-Whitney U test showed a significant increase (p < 0.001) in the toe clearance (within 34% to 64% of the swing phase from the toe-off instance) and FSA, from 87.60 mm and - 5.43degrees respectively during without cue to 94.29 mm and 2.93degrees respectively during with cue walking condition except in one subject. These findings support the potential incorporation of an FSA-based cueing device for toe clearance improvement among PD patients. In addition, the wearable setup supports the cueing device applicability outside laboratory and home settings.

The effects of slope-adaptive prosthetic feet on sloped gait performance and quality in unilateral transtibial prosthesis users: A scoping review

Introduction

In non-impaired human locomotion, sagittal-plane slope adaptation of the foot-ankle complex is a volitional function driven by neuromotor control to support upright posture and forward ambulation. Loss of this adaptation due to transtibial amputation can lead to instability and compensatory motions as most commercially-available prosthetic feet do not permit automatic slope adjustments. A selection of slope-adaptive feet (SAF) have been developed to promote biomimetic ankle motion while ambulating over slopes. This review evaluated the current literature to assess the effects of SAF prostheses on sloped gait performance in unilateral transtibial prosthesis users.

Methods

Four databases (PubMed, Embase, CINAHL, IEEE Xplore) were searched on April 28, 2022, for relevant articles. Search keywords covered the general terms "transtibial," "amputation," "slope," "adaptive," and "gait", and included articles comparing a SAF prosthesis to a non-SAF prosthesis condition. Data were extracted for analysis and results were grouped according to outcomes to identify trends and aid interpretation of slope adaptation effects on gait.

Results

Of the 672 articles screened, 24 met the selection criteria and were included in this review, published between 2009 and 2022. The non-SAF condition included dynamic response feet and SAF prostheses with the adaptability function inactive. Outcomes included biomechanical variables (joint dynamics, gait symmetry, toe clearance), clinical outcome measures, and energy expenditure. All SAF demonstrated some form of foot-ankle slope gradient adaptability, but effects on other joint dynamics were inconsistent. Minimum toe clearance during incline and decline walking was greater when using SAF compared to non-SAF in all reporting studies.

Conclusions

Results generally suggest improvements in gait quality, comfort, and safety with use of SAF compared to non-SAF during slope walking. However, variations in tested SAF and walking gradients across studies highlight the need for research to elucidate walking condition effects and advantages of specific designs.

Clinical Relevance

Slope-adaptive prosthetic feet may improve user gait quality and comfort and enhance gait safety by increasing minimum toe clearance. Patients who encounter slopes regularly should be considered as potential users of SAF if indicated appropriately.

Females Present Reduced Minimum Toe Clearance During Walking As Compared to Males in Active Older Adults

BACKGROUND

Physical decline due to aging has been associated with the risk of falls. Minimum toe clearance (MTC) is a gait parameter that might play a role in the mechanism of tripping and falling. However, it is unclear if there are any sex-related effects regarding MTC as people age. The present study investigated if there are sex-related differences in MTC in older active adults.

METHODS

Twenty-three females and 23 males (F: 65.5 ± 4.8 years; M: 61.9 ± 5.2 years) walked on a treadmill at a preferred walking speed, while kinematic data were obtained at a sampling frequency of 100 Hz and up-sampled to 120 and 240 Hz. MTC was calculated from the kinematics data and evaluated concerning its magnitude (ie, MTC and MTC/leg length), the time between left/right MTC (ie, T-MTC), amount of variability (ie, coefficient of variation [CV] and coefficient of variation modified [CVm]), and temporal structure of variability, that is, the complexity of the time series (ie, MTC α, T-MTC α).

RESULTS

No sex effects were found for MTC/leg length, for the amount of variability (ie, CV and CVm), and for the complexity of the time series (MTC α, T-MTC α). However, females exhibited significantly lower MTC and T-MTC after adjusting for walking speed, mass, and age as covariates.

CONCLUSIONS

The reduced MTC in females suggests a potential sex-related disparity in the risk of tripping and falling among active older adults.

Functional electrical stimulation during walking in children with unilateral spastic cerebral palsy: A randomized cross-over trial

AIM

To study if functional electrical stimulation (FES) of the peroneal nerve, which activates dorsiflexion, can improve body functions, activities, and participation and could be an effective alternative treatment in individuals with unilateral spastic cerebral palsy (CP).

METHOD

A randomized cross-over trial was performed in 25 children with unilateral spastic CP (classified in Gross Motor Function Classification System levels I and II) aged 4 to 18 years (median age at inclusion 9 years 8 months, interquartile range = 7 years-13 years 8 months), 15 patients were male. The study consisted of two 12-week blocks of treatment, that is, conventional treatment (ankle foot orthosis [AFO] or adapted shoes) and FES, separated by a 6-week washout period. Outcome measures included the Goal Attainment Scale (GAS), the Cerebral Palsy Quality of Life questionnaire, and a three-dimensional gait analysis.

RESULTS

Eighteen patients completed the trial. The proportion of GAS goals achieved was not significantly higher in the FES versus the conventional treatment phase (goal 1 p = 0.065; goal 2 p = 1.00). When walking while stimulated with FES, ankle dorsiflexion during mid-swing decreased over time (p = 0.006, average decrease of 4.8° with FES), with a preserved increased ankle range of motion compared to conventional treatment (p < 0.001, mean range of motion with FES +10.1° compared to AFO). No changes were found in the standard physical examination or regarding satisfaction with orthoses and feelings about the ability to dress yourself. In four patients, FES therapy failed; in 12 patients FES therapy continued after the trial.

INTERPRETATION

FES is not significantly worse than AFO; however, patient selection is critical, and a testing period and thorough follow-up are needed.

Is foot clearance influenced by different types of dual task in once-only faller community-dwelling older adults?

BACKGROUND

Tripping is one of the main causes of falls in older adults and has an important association with minimum toe clearance (MTC). MTC variability while performing alternating (ADT) or concurrent (CDT) dual-task activities may be a useful gait parameter to differentiate once-only fallers from non-faller older adults.

RESEARCH QUESTION

Is the MTC variability influenced by ADT and CDT in once-only faller community-dwelling older adults?

METHODS

Twenty-two community-dwelling older adults with a self-report of up to one fall in the last 12 months were allocated to the fallers group and 38 to the non-fallers group. Gait data were collected by two foot-worn inertial sensors (Physilog® 5, GaitUp, Lausanne, Switzerland). MTC mean magnitude and variability, as well as the stride-to-stride variability, stride time and length, lower limb peak angular velocity, and foot forward linear speed at the MTC instant, were calculated across approximately 50 gait cycles for each participant and condition using the GaitUp Analyzer software (GaitUp, Lausanne, Switzerland). The statistical analyzes were performed in the Statistical Package for the Social Sciences (SPSS), v.22.0, using generalized mixed linear models, adopting an alpha of 5%.

RESULTS AND SIGNIFICANCE

No interaction effect was observed; however, faller participants reduced the MTC variability (standard deviation) [(mean difference, MD = -0.099 cm; confidence interval, 95%CI = -0.183 to -0.015)], regardless of the condition. CDT compared to a single task (only gait) reduced the mean magnitude of the foot forward linear speed (MD=-0.264 m/s; 95%CI=-0.462 to -0.067), peak angular velocity (MD = -25.205 degrees/s; 95%CI = -45.507 to -4.904), and gait speed (MD = -0.104 m/s; 95%CI = -0.179 to -0.029), regardless of the group. These results suggest that MTC variability, regardless of condition, may be a promising gait parameter to differentiate once-only faller community-dwelling older adults from non-fallers.

Sex Differences in Spatiotemporal Gait Parameters of Transtibial Amputees

Research addressing lower limb amputee gait and prosthetic design often focuses on men, despite female lower limb amputees having different risk factors and lower success with their prosthetics overall. It is widely agreed that sex differences exist in able-bodied gait, but research analyzing sex differences in amputee gait is rare. This study compared male and female transtibial amputee gait to ascertain potential sex differences. Forty-five transtibial amputees were asked to walk at their self-selected speed, and spatiotemporal gait data were obtained. Both the mean and variability metric of parameters were analyzed for 10 male and 10 female participants. For all participants, amputated limbs had a shorter stance time, longer swing time, and larger step length. Females had a 10% shorter stance time and 26% larger normalized step and stride length than males. Female participants also walked over 20% faster than male participants. Finally, significant interactions were found in the mean and variability metric of stride velocity, indicating greater variability in women. These findings suggest that sex differences exist in transtibial amputee gait, offering possible explanations for the different comorbidities experienced by female lower limb amputees. These results have major implications for female amputees and for sex-specific research, rehabilitation, and prosthetic design.

Taping-induced cutaneous stimulation to the ankle tendons reduces minimum toe clearance variability

Large variability of minimum toe clearance (MTC) leads to a higher risk of tripping. Visual feedback-based gait training systems have been used to regulate MTC distribution, but these systems are expensive and bulky. Furthermore, the effect of such training lasts only for a short period of time. Considering the efficacy of elastic adhesive tape-induced cutaneous stimulation to the ankle tendons in improving proprioception and movement detection, we hypothesize that application of tapes to the ankle tendons as a practical method for modifying MTC distribution. To test this hypothesis, we recruited 13 young and healthy adults and instructed them to walk on a treadmill under four conditions: no taping, taping the tibialis anterior tendon, taping the Achilles tendon, and taping both tendons. We measured MTC distribution, lower limb joint angles and muscle activations of the tibialis anterior and gastrocnemius medialis, and compared these outcomes under the four conditions. The application of elastic adhesive tape to the ankle tendons had no significant effect on the average MTC height, but tapes applied to the Achilles tendon and both tendons significantly reduced MTC variability. Taping decreased the variability of some lower limb joint angles, but taping did not induce significant changes in the activation levels of the shank muscles. These results demonstrate that elastic adhesive tape applied to the shank can reduce MTC variability with minimal resistance, inertia and cumbersomeness.

Normalized kinematic walking symmetry data for individuals who use lower-limb prostheses: considerations for clinical practice and future research

Introduction

Individuals who use unilateral transtibial or transfemoral prostheses have negative secondary health effects associated with decreased kinematic (e.g., spatiotemporal and joint angle) walking symmetry between prosthetic and intact limbs. Research studies have quantified kinematic walking symmetry, but studies can be difficult to compare owing to the inclusion of small sample sizes and differences in participant demographics, biomechanical parameters, and mathematical analysis of symmetry. This review aims to normalize kinematic walking symmetry research data across studies by level of limb loss and prosthetic factors to inform considerations in clinical practice and future research.

Methods

A search was performed on March 18, 2020, in PubMed, Scopus, and Google Scholar to encompass kinematic walking symmetry literature from the year 2000. First, the most common participant demographics, kinematic parameters, and mathematical analysis of symmetry were identified across studies. Then, the most common mathematical analysis of symmetry was used to recalculate symmetry data across studies for the five most common kinematic parameters.

Results

Forty-four studies were included in this review. The most common participant demographics were younger adults with traumatic etiology who used componentry intended for higher activity levels. The most common kinematic parameters were step length, stance time, and sagittal plane ankle, knee, and hip range of motion. The most common mathematical analysis was a particular symmetry index equation.

Conclusions

Normalization of data showed that symmetry tended to decrease as level of limb loss became more proximal and to increase with prosthetic componentry intended for higher activity levels. However, most studies included 10 or fewer individuals who were active younger adults with traumatic etiologies.

Clinical Relevance

Data summarized in this review could be used as reference values for rehabilitation and payer justification. Specifically, these data can help guide expectations for magnitudes of walking symmetry throughout rehabilitation or to justify advanced prosthetic componentry for active younger adults under 65 years of age with traumatic etiologies to payers.

The Influence of Transtibial Prosthesis Type on Lower-Body Gait Adaptation: A Case Study

Gait parameters are altered and asymmetrical in individuals with transtibial amputation. The purpose of this study was to evaluate and compare the effect of four different prosthetic feet on lower-limb biomechanics during gait. A 34-year-old man with transtibial amputation performed four gait analysis sessions with four foot-ankle prostheses (Variflex, Meridium, Echelon, and Kinterra). Kinematic and kinetic parameters and gait symmetry were analyzed in different prosthetic conditions. The type of prosthesis had little effect on the participant's spatiotemporal parameters. Throughout the stance phase, increased hip angle, reduced knee flexion and ankle dorsiflexion were observed in the amputated leg. For kinetic parameters, reduced propulsive force (SI = 0.42-0.65), reduced knee extension moment (mainly during Echelon and Kinterra conditions, SI = 0.17 and 0.32, respectively), and increased knee abduction moment (mainly during the Variflex and Meridium, SI = 5.74 and 8.93, respectively) were measured in the amputated leg. Lower support moments were observed in the amputated leg as compared to the unaffected leg, regardless of the type of prosthesis (SI = 0.61-0.80). The prostheses tested induced different lower-limb mechanical adaptations. In order to achieve the clinical goal of better gait symmetry between lower limbs, an objective gait analysis could help clinicians to prescribe prosthetic feet based on quantitative measurement indicators to optimize gait rehabilitation.

Application of vibration to the soles reduces minimum toe clearance variability during walking

Minimum toe clearance (MTC) is an important indicator of the risk of tripping. Aging and neuromuscular diseases often decrease MTC height and increase its variability, leading to a higher risk of tripping. Previous studies have developed visual feedback-based gait training systems to modify MTC. However, these systems are bulky and expensive, and the effects of the training continue only for a short time. We paid attention to the efficacy of vibration in decreasing the variability of gait parameters, and hypothesized that proper vibration applied to soles can reduce the MTC variability. Using shoes embedded with active vibrating insoles, we assessed the efficacy of both sub- and supra-threshold vibration in affecting MTC distribution. Experiment results with 17 young and healthy adults showed that vibration applied throughout the walking task with constant intensity of 130% of sensory threshold significantly decreased MTC variability, whereas sub-threshold vibration yielded no significant effect. These results demonstrate that a properly designed tactile sensory input which is controlled and delivered by a simple wearable device, the active insole, can reduce the MTC variability during walking.

Investigating the Effect of Real-Time Center of Pressure (CoP) Feedback Training on the Swing Phase of Lower Limb Kinematics in Transfemoral Prostheses with SACH foot

Transfemoral amputee often encounters reduced toe clearance resulting in trip-related falls. Swing phase joint angles have been shown to influence the toe clearance therefore, training intervention that targets shaping the swing phase joint angles can potentially enhance toe clearance. The focus of this study was to investigate the effect of the shift in the location of the center of pressure (CoP) during heel strike on modulation of the swing phase joint angles in able-bodied participants (n=6) and transfemoral amputees (n=3). We first developed a real-time CoP-based visual feedback system such that participants could shift the CoP during treadmill walking. Next, the kinematic data were collected during two different walking sessions- baseline (without feedback) and feedback (shifting the CoP anteriorly/posteriorly at heel strike to match the target CoP location). Primary swing phase joint angle adaptations were observed with feedback such that during the mid-swing phase, posterior CoP shift feedback significantly increases (p<0.05) the average hip and knee flexion angle by 11.55 degrees and 11.86 degrees respectively in amputees, whereas a significant increase (p<0.05) in ankle dorsiflexion, hip and knee flexion angle by 3.60 degrees, 3.22 degrees, and 1.27 degrees respectively compared to baseline was observed in able-bodied participants. Moreover, an opposite kinematic adaptation was seen during anterior CoP shift feedback. Overall, results confirm a direct correlation between the CoP shift and the modulation in the swing phase lower limb joint angles.

An algorithm for real time minimum toe clearance estimation from signal of in-shoe motion sensor

An algorithm has been constructed for estimating minimum toe clearance (MTC), an important gait parameter previously proven to be a critical indicator of tripping risk. It uses data from a previously reported in-shoe motion sensor (IMS) for detecting gait events. First, candidate feature points in the IMS signal for use in detecting MTC events were identified. Then, the temporal agreement between each feature point and target MTC event was evaluated. Next, the accuracy and precision of the MTC estimated using each feature point was evaluated using a reference value obtained using a 3-D optical motion-capture system. The MTC was estimated using a geometric model and the IMS signal corresponding to the predicted MTC event. Once the best candidate feature point was identified, a real-time MTC estimation algorithm for use with an IMS was constructed. The mean values and standard deviations of measured foot motions obtained in a previous study were used for evaluating accuracy and precision. The results suggest that MTC events can be estimated by detecting the crossing point between the acceleration waveforms in the anterior-posterior and superior-inferior directions in an accuracy of 2.0% gait cycle. Using this feature point enables the MTC to be estimated in real time with an accuracy of 8.6 mm, which will enable monitoring of MTC in daily living.

A Scoping Review on Minimum Foot Clearance: An Exploration of Level-Ground Clearance in Individuals with Abnormal Gait

Background: Falls are a major health concern, with one in three adults over the age of 65 falling each year. A key gait parameter that is indicative of tripping is minimum foot clearance (MFC), which occurs during the mid-swing phase of gait. This is the second of a two-part scoping review on MFC literature. The aim of this paper is to identify vulnerable populations and conditions that impact MFC mean or median relative to controls. This information will inform future design/maintenance standards and outdoor built environment guidelines. Methods: Four electronic databases were searched to identify journal articles and conference papers that report level-ground MFC characteristics. Two independent reviewers screened papers for inclusion. Results: Out of 1571 papers, 43 relevant papers were included in this review. Twenty-eight conditions have been studied for effects on MFC. Eleven of the 28 conditions led to a decrease in mean or median MFC including dual-task walking in older adults, fallers with multiple sclerosis, and treadmill walking. All studies were conducted indoors. Conclusions: The lack of standardized research methods and covariates such as gait speed made it difficult to compare MFC values between studies for the purpose of defining design and maintenance standards for the outdoor built environment. Standardized methods for defining MFC and an emphasis on outdoor trials are needed in future studies.

Design and Validation of a Real-Time Visual Feedback System to Improve Minimum Toe Clearance (mTC) in Transfemoral Amputees

Tripping is accompanied by reduced minimum toe clearance (mTC) during the swing phase of gait. The risk of fall due to tripping among transfemoral amputees is nearly 67% which is greater than the transtibial amputees. Therefore, intervention to improve mTC can potentially enhance the quality of life among transfemoral amputees. In this paper, we first develop a real-time visual feedback system with center of pressure (CoP) information. Next, we recruited six non-disabled and three transfemoral amputees to investigate the effect on mTC while participants were trained to shift the CoP anteriorly/posteriorly during heel strike. Finally, to assess the lasting effect of training on mTC, retention trials were conducted without feedback. During feedback, posterior shift in the CoP improved the mTC significantly from 4.68 ± 0.40 cm to 6.12 ± 0.68 cm (p < 0.025) in non-disabled participants. A similar significant improvement in mTC from 4.60 ± 0.55 cm to 5.62 ± 0.57 cm was observed in amputees during posterior shift of CoP. Besides mTC, maximal toe clearances, i.e., maxTC₁ and maxTC₂, also showed a significant increase (p < 0.025) during the posterior shift of CoP in both the participants. Moreover, during retention, mTC did not differ significantly (p > 0.05) from feedback condition in amputee, suggesting a positive effect of feedback training. The foot-to-ground angle (FGA) at mTC increased significantly (p < 0.025) during posterior shift feedback in non-disabled suggests active ankle dorsiflexion in increasing mTC. However, in amputees, FGA at mTC did not differ significantly during both anterior and posterior CoP shift feedback. The present findings suggest CoP feedback as a potential strategy during gait rehabilitation of transfemoral amputees.

A cross-sectional study of foot-ground clearance in healthy community dwelling Japanese cohorts aged 50, 60 and 70 years

BACKGROUND

Falls-related injuries are particularly serious for older people, causing pain, reduced community engagement and associated medical costs. Tripping is the leading cause of falls and the current study examined whether minimum ground clearance (MFC) of the swing foot, indicating high tripping risk, would be differentiated across cohorts of healthy 50-, 60- and 70-years old community residents in Japan.

METHODS

A cross-sectional population comprising the three groups (50s, 60s and 70s) of 123 Konosu City residents consented to be recorded when walking on an unobstructed surface at preferred speed. Gait biomechanics was measured using high speed (100 Hz) motion capture (OptiTrack - Natural Point Inc.), including step length and width, double support, foot contact angle and MFC (swing toe height above the ground). Multivariate Analysis of Variance (MANOVA) was used to confirm ageing effects on MFC and fundamental gait parameters. Pearson's correlations were performed to identify the relationships between mean MFC and other MFC characteristics (SD and SI), step length, step width, double support time and foot contact angle.

RESULTS

Compared to 50s, lower step length was seen (2.69 cm and 6.15 cm) for 60s and 70s, respectively. No other statistical effects were identified for spatio-temporal parameters between the three groups. The 50s cohort MFC was also significantly higher than 60s and 70s, while step-to-step MFC variability was greater in the 70s than 50s and 60s. Pearson's correlations demonstrated that more symmetrical gait patterns were associated with greater MFC height, as reflected in greater symmetry in step width (50s), MFC (60s) and foot contact angle (70s). In the 70s increased MFC height correlated with higher MFC variability and reduced foot contact angle.

CONCLUSIONS

MFC height reduces from 60 years but more variable MFC appears later, from 70 years. While symmetrical gait was accompanied by increased MFC height, in the 70s group attempts to increase MFC height may have caused more MFC variability and lower foot contact angles, compromising foot-ground clearance. Assessments of swing foot mechanics may be a useful component of community falls prevention.

Minimum toe clearance and tripping probability in people with unilateral transtibial amputation walking on ramps with different prosthetic designs

BACKGROUND

Minimum Toe Clearance (MTC) is defined as the minimum vertical distance between the lowest point under the front part of the foot and the ground, during mid-swing. Low values of MTC and walking on inclines are both related to higher probability of tripping and falling in lower limb amputees. New prosthetic designs aim at improving MTC, especially on ramps, however the real effect on MTC still needs investigation. The objective of this study was then to evaluate the effect of different prosthetic designs on MTC in inclined walking.

METHODS

Thirteen transtibial amputees walked on a ramp using three different prostheses: non articulating ankle (NAA), articulating hydraulic ankle (AHA), and articulating hydraulic ankle with microprocessor (AHA-MP). Median MTC, coefficient of variation (CV), and tripping probability (TP) for obstacles of 10 and 15 mm were compared across ankle type in ascent and descent.

FINDINGS

When using AHA-MP, larger MTC median values for ascending (P ≤ 0.001, W = 0.58) and descending the ramp (P = 0.003, W = 0.47) were found in the prosthetic limb. Also significantly lower CV was found on the prosthetic limb for both types of AHA feet when compared to NAA for descending the ramp (P = 0.014, W = 0.45). AHA-MP showed the lowest TP for the prosthetic leg in three conditions evaluated. On the sound limb results showed the median MTC was significantly larger (P = 0.009, W = 0.43) and CV significantly lower (P = 0.005, W = 0.41) when using an AHA in ascent.

INTERPRETATION

Both AHA prosthetic designs help reduce the risk of tripping of the prosthetic limb by increasing the median MTC, lowering its variability and reducing TP for both legs when ascending and descending the ramp. For most of the conditions, AHA-MP showed the lowest TP values. Findings suggest that AHA prostheses, especially AHA-MP could reduce the risk of tripping on ramps in amputees.

Gait symmetry in the dual task condition as a predictor of future falls among independent older adults: a 2-year longitudinal study

BACKGROUND

Given the potential consequences of falls among older adults, a major challenge is to identify people at risk before the first event. In this context, gait parameters have been suggested as markers of fall risk.

AIM

To examine, among older people, the prospective relationship between gait patterns assessed in comfortable and challenging walking conditions, and future fall(s).

METHOD

A total of 105 adults older than 65 years, living independently at home and without a recent fall history were included in a 2-year, longitudinal, observational study. All underwent physical and functional assessment. Gait speed, stride length, frequency, symmetry and regularity and Minimum Toe Clearance (MTC) were recorded in comfortable (CW), fast (FW) and dual task walking (DTW) conditions. Gait parameter changes occurring between CW and FW and between CW and DTW were calculated and expressed in percent. DTW cost was calculated as the change of DTW relative to CW. Fall events were recorded using fall diaries. Comparisons according to fall occurrence were performed by means of univariate analysis and multivariate binary logistic regression analysis.

RESULTS

Two-year follow-up was available for 96 participants, of whom 35 (36.5%) fell at least once. Comparative analysis showed that future fallers had shorter FW stride length and higher symmetry DTW cost than non-fallers (p < 0.05). Binary logistic regression analysis showed that each additional percent of stride symmetry cost was associated with an increase in future fall risk (odds ratio 1.018, 95% Confidence Interval (CI) 1.002-1.033; p = 0.027).

DISCUSSION

Our results confirm the association between a symmetry decrease in DTW and future fall(s). Indeed in this study, the mean symmetry DTW cost in fallers is almost 20% higher than in non-fallers, meaning a fall risk that is around 36% higher than among non-fallers.

CONCLUSION

This exploratory study shows the usefulness of considering gait parameters, particularly symmetry in challenging walking conditions, for early identification of future fallers.

Energy cost of ambulation in trans-tibial amputees using a dynamic-response foot with hydraulic versus rigid 'ankle': insights from body centre of mass dynamics

BACKGROUND

Previous research has shown that use of a dynamic-response prosthetic foot (DRF) that incorporates a small passive hydraulic ankle device (hyA-F), provides certain biomechanical benefits over using a DRF that has no ankle mechanism (rigA-F). This study investigated whether use of a hyA-F in unilateral trans-tibial amputees (UTA) additionally provides metabolic energy expenditure savings and increases the symmetry in walking kinematics, compared to rigA-F.

METHODS

Nine active UTA completed treadmill walking trials at zero gradient (at 0.8, 1.0, 1.2, 1.4, and 1.6 of customary walking speed) and for customary walking speed only, at two angles of decline (5° and 10°). The metabolic cost of locomotion was determined using respirometry. To gain insights into the source of any metabolic savings, 3D motion capture was used to determine segment kinematics, allowing body centre of mass dynamics (BCoM), differences in inter-limb symmetry and potential for energy recovery through pendulum-like motion to be quantified for each foot type.

RESULTS

During both level and decline walking, use of a hyA-F compared to rigA-F significantly reduced the total mechanical work and increased the interchange between the mechanical energies of the BCoM (recovery index), leading to a significant reduction in the metabolic energy cost of locomotion, and hence an associated increase in locomotor efficiency (p < 0.001). It also increased inter-limb symmetry (medio-lateral and progression axes, particularly when walking on a 10° decline), highlighting the improvements in gait were related to a lessening of the kinematic compensations evident when using the rigA-F.

CONCLUSIONS

Findings suggest that use of a DRF that incorporates a small passive hydraulic ankle device will deliver improvements in metabolic energy expenditure and kinematics and thus should provide clinically meaningful benefits to UTAs' everyday locomotion, particularly for those who are able to walk at a range of speeds and over different terrains.

Foot-ground clearance characteristics in women: A comparison across different ages

BACKGROUND

Tripping is a common event leading to falls amongst elderly. Minimum foot clearance (MFC) is a critical swing phase control factor associated with tripping and falls.

RESEARCH QUESTION

Are there differences in MFC characteristics among three age groups of women and are there association between MFC and lower limb kinematics?

METHODS

Cross-sectional observational study. Three-dimensional gait analysis of 55 healthy women. ANOVA was used to compare (p<0.05) MFC characteristics among young, middle-aged and elderly groups. Multiple Linear Regression Analysis was used to test prediction over MFC.

RESULTS

Elderly women walked slower, with lower MFC and lower maximum foot velocity during swing (MFV) than young and middle-aged women. There were more hip flexion and less ankle dorsiflexion during MFC among elderly. There is a strong positive relationship between dorsiflexion and MFC. And ankle dorsiflexion was the most predictive variable over MFC.

SIGNIFICANCE

Elderly women walk slower with lower MFC value and less ankle dorsiflexion than gender-matched young controls. Increased hip flexion may represent a gait adaptation to avoid tripping. Gait speed had no effect on those findings.

Self-Selected walking speed increases when individuals are aware of being recorded

BACKGROUND

Typical gait data collections consist of discrete walking trials where participants are aware when data are being recorded. Anecdotally, some investigators have reported that participants often walk differently between trials or before or after data collection compared to when they know they are being recorded. In addition, walking speed, which affects a number of gait variables, is known to be different when individuals complete discrete and continuous walking trials.

RESEARCH QUESTION

The purpose of this study was to determine whether changes in walking speed occurred as a result of participants being aware, versus unaware that data were being recorded, during both discrete and continuous walking trials.

METHODS

Kinematic data were collected for twenty two individuals walking continuous trials or discrete trials, while they were both aware and unaware of being recorded. Comparisons of walking speeds were made between groups (continuous walking; discrete trials) and awareness of being recorded (aware; unaware) using a two way ANOVA.

RESULTS

The results indicated that participants walked significantly faster during discrete trials when they were aware that data were being recorded compared to when they were unaware. However, when they walked continuously their walking speed was not affected by their awareness.

SIGNIFICANCE

The results suggest that awareness of data collection, and the type of protocol used during data collection, affect an individual's walking speed during gait analysis. Therefore, care should be taken when determining gait analysis protocols where variables are sensitive to walking speeds.

A Principal Components Analysis Approach to Quantifying Foot Clearance and Foot Clearance Variability

Low foot clearance and high variability may be related to falls risk. Foot clearance is often defined as the local minimum in toe height during swing; however, not all strides have this local minimum. The primary purpose of this study was to identify a nondiscrete measure of foot clearance during all strides, and compare discrete and nondiscrete measures in ability to rank individuals on foot clearance and variability. Thirty-five participants (young adults [n = 10], older fallers [n = 10], older nonfallers [n = 10], and stroke survivors [n = 5]) walked overground while lower extremity 3D kinematics were recorded. Principal components analysis (PCA) of the toe height waveform yielded representation of toe height when it was closest to the ground. Spearman's rank order correlation assessed the association of foot clearance and variability between PCA and discrete variables, including the local minimum. PCA had significant (P < .05) moderate or strong associations with discrete measures of foot clearance and variability. An approximation of the discrete local minimum had a weak association with PCA and other discrete measures of foot clearance. A PCA approach to quantifying foot clearance can be used to identify the behavioral components of toe height when it is closest to the ground, even for strides without a local minimum.

A personalised exercise programme for individuals with lower limb amputation reduces falls and improves gait biomechanics: A block randomised controlled trial

BACKGROUND

Lower limb amputees (LLAs) are at increased risk of falling due to the inherent asymmetry resulting from their limb loss, muscle weakness and other neuro-musculoskeletal limitations.

RESEARCH QUESTION

The aim of this study was to evaluate the effects of a personalised exercise programme on falls prevention and gait parameters in LLAs.

METHODS

Fifteen LLAs, recruited from their local prosthetic services centre, were block randomised, by age and level of amputation, into two groups: exercise group (transfemoral, n = 5; transtibial, n = 2) and control group (transfemoral, n = 5; transtibial, n = 3). The exercise group completed a 12-week programme, focusing on strength, balance, flexibility and walking endurance, delivered in group sessions at the University, and combined with a personalised home exercise programme. Temporal-spatial, 3D kinematic and kinetic gait parameters were collected at baseline and post-intervention. Falls incidence was also followed up at 12 months.

RESULTS

The exercise group experienced significantly fewer falls in the one-year period from baseline, compared with the average annual falls rate, obtained at baseline (P = 0.020; d = 1.54). Gait speed in the exercise group increased by 0.21 m∙s^-1, to 0.98 m∙s^-1  (P < 0.001; d = 0.91), through increased intact limb cadence. In the pre-swing phase, there were significant increases in intact limb peak vertical force, and affected limb peak propulsive (anterior) force for the exercise group. Power absorption and generation significantly increased at both the intact and affected hip joints (H3) and the intact ankle (A1 and A2) for the exercise group, resulting in significant group*time interactions.

SIGNIFICANCE

This is the first study to document the clinically meaningful benefits of an exercise intervention for falls prevention and gait performance in LLAs. Specialised exercise programmes for community-dwelling LLAs should be implemented as a method to reduce falls and improve walking performance in this population.

A Comparison of Self-Selected Walking Speeds and Walking Speed Variability When Data Are Collected During Repeated Discrete Trials and During Continuous Walking

A typical gait analysis data collection consists of a series of discrete trials, where a participant initiates gait, walks through a motion capture volume, and then terminates gait. This is not a normal 'everyday' gait pattern, yet measurements are considered representative of normal walking. However, walking speed, a global descriptor of gait quality that can affect joint kinematics and kinetics, may be different during discrete trials, compared to continuous walking. Therefore, the purpose of this study was to investigate the effect of continuous walking versus discrete trials on walking speed and walking speed variability. Data were collected for 25 healthy young adults performing 2 walking tasks. The first task represented a typical gait data collection session, where subjects completed repeated trials, beginning from a standstill and walking along a 12-m walkway. The second task was continuous walking along a "figure-of-8" circuit, with 1 section containing the same 12-m walkway. Walking speed was significantly higher during the discrete trials compared to the continuous trials (p < .001), but there were no significant differences in walking speed variability between the conditions. The results suggest that choice of gait protocol may affect results where variables are sensitive to walking speed.

Relating minimum toe clearance to prospective, self-reported, trip-related stumbles in the community

BACKGROUND

Individuals with transtibial amputation are at increase risk of falling. The absence of an ankle joint and the associated musculature in these individuals can reduce clearance between the prosthetic foot and ground during the swing phase of gait, which may increase the risk of stumbling and in turn falling.

OBJECTIVES

To associate minimum toe clearance during gait in the laboratory with community-based, trip-related stumbles by individuals with transtibial amputation using conventional feet.

STUDY DESIGN

Prospective cohort design; following quantitative gait analysis, participants completed electronic surveys to prospectively report stumbles and falls for 1 year thereafter.

METHODS

General community with gait analysis conducted within a motion analysis laboratory and prospective tracking of stumbles occurring in the community. A volunteer sample of eight unilateral, transtibial amputees that were K3 or K4 level ambulators and current patients at a local prosthetic clinic. All participants completed the entire 1-year follow-up study. Prosthetic-side minimum toe clearance while walking on a level treadmill at self-selected speed and self-reported trip-related stumbles in the community. Minimum toe clearance was defined as a local minimum of the vertical displacement of the toe from toe-off to heelstrike relative to its position during midstance.

RESULTS

Prosthetic-side minimum toe clearance was more than 50% lower for participants who reported one or more trip-related stumbles on that side compared with participants who reported zero trip-related stumbles on the prosthetic side (minimum toe clearance = 12.3 ± 0.8 mm vs 25.6 ± 5.4 mm, respectively; p = 0.036).

CONCLUSION

This is the first study relating laboratory-based measures to prospective stumbles by prosthesis users. The results suggest that prosthesis users with low minimum toe clearance may be at increased risk of experiencing a trip-related stumble in the community. Given that frequent stumbling increases the risk of falling, future work is warranted on the effectiveness of interventions focused on minimum toe clearance on reducing fall risk. Clinical relevance Interventions to increase minimum toes clearance, which could include prescription of active dorsiflexing prostheses or gait training, may help reduce the risk of trip-related falls for individuals who report a history of trip-related stumbles.

Minimum toe clearance: probing the neural control of locomotion

Minimum toe clearance (MTC) occurs during a highly dynamic phase of the gait cycle and is associated with the highest risk of unintentional contact with obstacles or the ground. Age, cognitive function, attention and visual feedback affect foot clearance but how these factors interact to influence MTC control is not fully understood. We measured MTC in 121 healthy individuals aged 20–80 under four treadmill walking conditions; normal walking, lower visual field restriction and two Stroop colour/word naming tasks of two difficulty levels. Competition for cognitive and attentional resources from the Stroop task resulted in significantly lower mean MTC in older adults, with the difficult Stroop task associated with a higher frequency of extremely low MTC values and subsequently an increased modelled probability of tripping in this group. While older adults responded to visual restriction by markedly skewing MTC distributions towards higher values, this condition was also associated with frequent, extremely low MTC values. We reveal task-specific, age-dependent patterns of MTC control in healthy adults. Age-related differences are most pronounced during heavy, distracting cognitive load. Analysis of critically-low MTC values during dual-task walking may have utility in the evaluation of locomotor control and fall risk in older adults and patients with motor control deficits.

A new measure of trip risk integrating minimum foot clearance and dynamic stability across the swing phase of gait

Minimum toe clearance (MTC) is thought to quantify the risk of the toe contacting the ground during the swing phase of gait and initiating a trip, but there are methodological issues with this measure and the risk of trip-related falls has been shown to also be associated with gait speed and dynamic stability. This paper proposes and evaluates a new measure, trip risk integral (TRI), that circumvents many issues with MTC as typically calculated at a single point by considering minimum foot clearance across the entire swing phase and taking into account dynamic stability to estimate risk of falling due to a trip rather than risk of the foot contacting the floor. Shoes and floor surfaces were digitized and MTC and TRI calculated for unimpaired younger (N=14, age=26±5), unimpaired older (N=14, age=73±7), and older adults who had recently fallen (N=11, age=72±5) walking on surfaces with no obstacles, visible obstacles, and hidden obstacles at slow, preferred, and fast gait speeds. MTC and TRI had significant (F≥5, p≤0.005) but differing effects of gait speed and floor surface. As gait speed increased (which increases risk of trip-related falls) MTC indicated less and TRI greater risk, indicating that TRI better quantifies risk of falling due to a trip. While MTC and TRI did not differ by subject group, strong speed-related effects of TRI (F≥8, p≤0.0007) resulted in improved TRI for fallers due to their slower self-selected preferred gait. This demonstrates that slower gait is both an important covariate and potential intervention for trip-related falls.

Determinants of preferred ground clearance during swing phase of human walking

During each step of human walking, the swing foot passes close to the ground with a small but (usually) non-zero clearance. The foot can occasionally scuff against the ground, with some risk of stumbling or tripping. The risk might be mitigated simply by lifting the foot higher, but presumably at increased effort, of unknown amount. Perhaps the normally preferred ground clearance is a trade-off between competing costs, one for lifting the foot higher and one for scuffing it. We tested this by measuring the metabolic energy cost of lifting and scuffing the foot, treating these apparently dissimilar behaviors as part of a single continuum, where scuffing is a form of negative foot lift. We measured young, healthy adults (N=9) lifting or scuffing the foot by various amounts mid-swing during treadmill walking, and observed substantial costs, each well capable of doubling the net metabolic rate for normal walking (gross cost minus that for standing). In relative terms, the cost for scuffing increased over twice as steeply as that for lifting. That relative difference means that the expected value of cost, which takes into account movement variability, occurs at a non-zero mean clearance, approximately matching the preferred clearance we observed. Energy cost alone is only a lower bound on the overall disadvantages of inadvertent ground contact, but it is sufficient to show how human behavior may be determined not only by the separate costs of different trade-offs but also by movement variability, which can influence the average cost actually experienced in practice.