Changes in Dynamic Mean Ankle Moment Arm in Unimpaired Walking Across Speeds, Ramps, and Stairs.

Understanding the natural biomechanics of walking at different speeds and activities is crucial to develop effective assistive devices for persons with lower-limb impairments. While continuous measures such as joint angle and moment are well-suited for biomimetic control of robotic systems, whole-stride summary metrics are useful for describing changes across behaviors and for designing and controlling passive and semi-active devices. Dynamic mean ankle moment arm (DMAMA) is a whole-stride measure representing the moment arm of the ground reaction impulse about the ankle joint-effectively, how "forefoot-dominated" or "hindfoot-dominated" a movement is. DMAMA was developed as a target and performance metric for semi-active devices that adjust once per stride. However, for implementation in this application, DMAMA must be characterized across various activities in unimpaired individuals. In our study, unimpaired participants walked at "slow," "normal," and "fast" self-selected speeds on level ground and at a normal self-selected speed while ascending and descending stairs and a 5-degree incline ramp. DMAMA measured from these activities displayed a borderline-significant negative sensitivity to walking speed, a significant positive sensitivity to ground incline, and a significant decrease when ascending stairs compared to descending. The data suggested a nonlinear relationship between DMAMA and walking speed; half of the participants had the highest average DMAMA at their "normal" speed. Our findings suggest that DMAMA varies substantially across activities, and thus, matching DMAMA could be a valuable metric to consider when designing biomimetic assistive lower-limb devices.

Socket-residuum coupling integrity affects perception of external stimuli: Effects of altering the transtibial interface using vacuum-assisted suspension.

BACKGROUND: Relative movement between the socket and residual limb can impair function in prosthesis users. It is plausible that, in addition to its mechanical effect, the integrity of the socket-residuum interface influences the ability of an individual to sense tactile cues through the prosthesis. Vacuum-assisted suspension (VAS) has been shown to reduce relative movement at this interface, providing a means to test this premise. The purpose of this pilot study was to assess the effects of altering socket-residuum interface integrity through the VAS pressure level on the thresholds of perception of an externally applied vibration stimulus. METHODS: Seven unilateral transtibial prosthesis users participated. Socket-residual limb integrity was altered using the VAS subatmospheric (vacuum) pressure level. Vibration perception tests were conducted at low, mid, and high vacuum levels, targeting 0, 8, and 19 in Hg respectively, and performed in partially loaded and fully loaded conditions. Vibration intensity was increased using a dial until participants delivered a verbal signal indicating it was perceptible, and the nominal intensity was recorded. RESULTS: Intensity thresholds decreased (ie, sensitivity increased) from low to high vacuum settings when fully loaded ( P = 0.008). Differences when partially loaded were nonsignificant and variable across participants. CONCLUSION: This study provides preliminary evidence that altering the integrity between the socket and residual limb by modifying the vacuum level affects sensation related to the external environment experienced through the prosthesis, although translation of these findings to real-world stimuli remains to be tested.

Categorization and recommendations for outcome measures for lower limb absence by an expert panel.

BACKGROUND: Understanding the psychometric strengths and limitations of outcome measures for use with people with lower limb absence (LLA) is important for selecting measures suited to evaluating patient outcomes, answering clinical and research questions, and informing health care policy. The aim of this project was to review the current psychometric evidence on outcome measures in people with LLA to determine which measures should be included in a stakeholder consensus process. METHODS: An expert panel was assembled, and a 3-stage review process was used to categorize outcome measures identified in a systematic literature review into 3 distinct categories (recommended for measures with better than adequate psychometric properties; recommended with qualification; and unable to recommend). Panelists were asked to individually categorize measures based on results of a systematic review of identified measures' psychometric properties. Each measure's final categorization was based on ≥70% agreement by all panelists. RESULTS: No outcome measure attained the ≥70% consensus threshold needed to achieve a rating of "recommend." Hence, panelists suggested combining "recommend" and "recommend with qualifications" into a single category of "recommend with qualifications." Using this approach, consensus was reached for 59 of 60 measures. Consensus could not be reached on 1 outcome measure (socket comfort score). Thirty-six outcome measures were categorized as "unable to recommend" based on available evidence; however, 23 (12 patient-reported measures and 11 performance-based measures) demonstrated adequate psychometric properties in LLA samples and were thus rated as "recommend with qualification" by the expert panel. The panel of experts were able to recommend 23 measures for inclusion in the subsequent stakeholder review. A key strength of this process was bringing together international researchers with extensive experience in developing and/or using LLA outcome measures who could assist in identifying psychometrically sound measures to include in a subsequent stakeholder consensus process. CONCLUSION: The above categorizations represent the current state of psychometric evidence on outcome measures for people with LLA and hence may change over time as additional research becomes available. The results will be used to achieve wider consensus from clinicians, health policymakers, health clinic managers, researchers, and end users (i.e., individuals with LLA) on outcome measures for the International Society of Prosthetics and Orthotics lower limb Consensus Outcome Measures for Prosthetic and Amputation ServiceS.

Sensorimotor function and standing balance in older adults with transtibial limb loss.

BACKGROUND: Limited research has focused on older prosthesis users despite the expected compounded effects of age and amputation on sensorimotor function, balance, and falls. This study compared sensorimotor factors and standing balance between older individuals with and without transtibial amputation, hypothesizing that prosthesis users would demonstrate worse sensorimotor function. Secondarily we assessed the relationship between standing balance and somatosensation in prosthesis users. METHODS: Thirteen persons with unilateral transtibial amputation (71.7 years) and 10 able-bodied controls (71.7 years) participated in this cross-sectional observational study. Passive joint range-of-motion, muscle strength, proprioception (joint position sense), tactile sensitivity, and standing balance (center-of-pressure sway) were compared between groups. A multiple linear regression analysis assessed the relationship between proprioception and balance (without vision) in prosthesis users. FINDINGS: Our hypotheses were generally not supported, with the only differences being reduced joint range-of-motion and strength in prosthesis users (with large effect sizes), but comparable sensation and balance. Notably, prosthesis users demonstrated better proprioception than controls as reflected through better joint position sense when the limb was non-weight bearing. Worse amputated limb proprioception was associated with better standing balance in prosthesis users. INTERPRETATION: Older prosthesis users have impaired passive joint motion and muscle strength compared to controls that could challenge their ability to position and control the amputated limb to avoid falls during daily activities. However, their better amputated limb proprioception might help counteract those limitations by leveraging sensory feedback from the suspended limb. The relationship between amputated limb proprioception and standing balance suggests a nuanced relationship that warrants further study.

Validating a fear-of-falling-related activity avoidance scale in lower limb prosthesis users.

BACKGROUND: Limited available data suggest that fear of falling (FoF) may be common among lower limb prosthesis users (LLPUs) and associated with negative rehabilitation outcomes. The impact of FoF on outcomes may be exacerbated when fear leads to self-imposed declines in activity. There is a need to identify the validity of fear-of-falling-related activity avoidance scales in LLPUs. OBJECTIVE: To evaluate the convergent, discriminant, and known-group construct validity of the modified Survey of Activities and FoF in the Elderly (mSAFE) for LLPUs. Secondarily, we sought to determine if the mSAFE scale could be reduced without losing information regarding construct validity. DESIGN: Online survey. SETTING: Not applicable. PARTICIPANTS: Fifty-nine persons with unilateral or bilateral amputation at the transtibial or transfemoral level, with ≥6 months experience using a definitive prosthesis for activities other than transfers. INTERVENTION: Participants completed an online survey that consisted of the mSAFE and questions to assess FoF (yes/no), fear-of-falling-related activity avoidance (yes/no), as well as previously validated scales capturing related and unrelated constructs. T-tests were used to compare mSAFE score between yes/no respondents for known-group construct validity. Correlations between mSAFE and previously validated surveys assessed convergent and discriminant validity. Analyses were repeated on a reduced number of mSAFE items following a redundancy analysis. MAIN OUTCOME MEASURES: Not applicable. RESULTS: Significant correlation coefficients of |0.440-0.825| were found for convergent validity with evidence of known-group construct validity (p < .021 for all comparisons). There was evidence for discriminant validity, with non-significant associations for two-of-three correlations. Results from validity analyses for a shortened 6-item mSAFE were similar to that for the full scale. CONCLUSION: This study provided initial evidence regarding validity of the mSAFE as a measure to assess fear-of-falling-related activity avoidance in LLPUs. A 6-item scale may be appropriate if the full scale would be taxing or time-consuming.

Dynamic Balance During Walking in Transfemoral Prosthesis Users: Step-to-Step Changes in Whole-Body and Segment Angular Momenta.

Transfemoral prosthesis users (TFPUs) typically have a high risk of balance loss and falling. Whole-body angular momentum ( [Formula: see text] is a common measure for assessing dynamic balance during human walking. However, little is known about how unilateral TFPUs maintain this dynamic balance through segment-to-segment cancellation strategies. Better understanding of the underlying mechanisms of dynamic balance control in TFPUs is required to improve gait safety. Thus, this study aimed to evaluate dynamic balance in unilateral TFPUs during walking at a self-selected constant speed. Fourteen unilateral TFPUs and fourteen matched controls performed level-ground walking at a comfortable speed on a straight, 10-m-long walkway. In the sagittal plane, the TFPUs had a greater and smaller range of [Formula: see text] compared to controls during intact and prosthetic steps, respectively. Further, the TFPUs generated greater average positive and negative [Formula: see text] than did the controls during intact and prosthetic steps, respectively, which may necessitate larger step-to-step postural changes in the forward and backward rotation about the body center of mass (COM). In the transverse plane, no significant difference was observed in the range of [Formula: see text] between groups. However, the TFPUs displayed smaller negative average [Formula: see text] in the transverse plane than did the controls. In the frontal plane, the TFPUs and controls demonstrated similar range of [Formula: see text] and step-to-step whole-body dynamic balance owing to the employment of different segment-to-segment cancellation strategies. Our findings should be interpreted and generalized with caution for the demographic features in our participants.

Footwear limitations in women prosthesis users relate to more than preference.

BACKGROUND: The option to wear desired footwear may be an important part of community reintegration after lower-limb amputation. OBJECTIVES: This study explored outcomes related to footwear, health, and participation in women Veterans with lower-limb amputation. METHODS: A cross-sectional questionnaire was mailed to all women Veterans age 18-82 years with major lower-limb amputation(s) who had received prosthetics services in the US Department of Veterans Affairs (N = 538). The questionnaire assessed Perceived Challenges (including clothing limitations, prosthetic foot limitations [width, height, and shape], and shoe avoidance for safety concerns), type of footwear used and preference, and included subscales from the Patient-Reported Outcome Measurement Information System, Amputee Body Image Scale Prosthetic Limb Users' Survey of Mobility, Community Participation Index, Activities-Specific Balance Confidence Scale, and Prosthesis Evaluation Questionnaire. Bivariate correlations examined relationships between a composite measure of Perceived Challenges and patient-reported outcomes. RESULTS: One hundred questionnaires were returned (18.6% response rate; 3 excluded for limited prosthesis use). The Perceived Challenges score was significantly correlated with scores for the Amputee Body Image Scale-Revised (r = 0.24, p = 0.019), Patient-Reported Outcome Measurement Information System (ability to participate: r = -0.25, p = 0.014), Prosthesis Evaluation Questionnaire (utility: r = -0.32, p = 0.001, appearance: r = -0.48, p < 0.001), Activities-Specific Balance Confidence Scale (r = -0.20, p = 0.046), and Prosthetic Limb Users' Survey of Mobility (r = -0.21, p = 0.036), but not depression or anxiety. CONCLUSIONS: Women who have greater issues with how their prosthesis affects the shoes and clothing they can wear also have poorer body image, reduced functional capabilities, and lower reported participation in activities. Improved prosthetic foot design may help to improve social participation and other important outcomes for women prosthesis users.

Systematic Assessment of Prosthesis Stiffness on User Biomechanics Using the Lower Leg Trajectory Error Framework and Its Implication for the Design and Evaluation of Ankle-Foot Prostheses.

Advances in understanding the effects the mechanical characteristics of prosthetic feet on user biomechanics have enabled passive prostheses to improve the walking pattern of people with lower limb amputation. However, there is no consensus on the design methodology and criteria required to maximize specific user outcomes and fully restore their mobility. The Lower Leg Trajectory Error (LLTE) framework is a novel design methodology based on the replication of lower leg dynamics. The LLTE value evaluates how closely a prosthetic foot replicates a target walking pattern. Designing a prosthesis that minimizes the LLTE value, optimizes its mechanical function to enable users to best replicate the target lower leg trajectory. Here, we conducted a systematic sensitivity investigation of LLTE-optimized prostheses. Five people with unilateral transtibial amputation walked overground at self-selected speeds using five prototype energy storage and return feet with varying LLTE values. The prototypes' LLTE values were varied by changing the stiffness of the participant's LLTE-optimized design by 60%, 80%, 120%, and 167%. Users most closely replicated the target able-bodied walking pattern with the LLTE-optimized stiffness, experimentally demonstrating that the predicted optimum was a true optimum. Additionally, the predicted LLTE values were correlated to the user's ability to replicate the target walking pattern, user preferences, and clinical outcomes including roll-over geometries, trunk sway, prosthetic energy return, and peak push-off power. This study further validates the use of the LLTE framework as a predictive and quantitative tool for designing and evaluating prosthetic feet.

Effects of footwear on the gait kinematics of women with unilateral transtibial amputation: an observational case series.

PURPOSE: Prosthesis geometry and behaviour limit the footwear options available to women. Using a commercially available prosthetic foot that permits user-alignment to accommodate shoes with different heel heights, we investigated the effect of footwear on gait kinematics, with and without adjustment for differences in heel-forefoot differential. MATERIALS AND METHODS: Three women with transtibial amputation walked at a self-selected pace, first in an athletic shoe (prosthetist-aligned; baseline condition), then (i) in a flatter shoe without realigning the prosthesis, and (ii) in flat and heeled shoes following user re-alignment. Kinematics in each condition were compared to baseline. RESULTS: Baseline gait patterns were highly variable across participants. Gait was slower in comparison to baseline in all conditions, but movement compensations varied across participants. An increased lower limb extension tendency was evident with the misaligned prosthesis. With user re-alignment to accommodate the shoe there were fewer deviations from baseline, however kinematic differences remained in both the flat and heeled shoes. CONCLUSIONS: The user-alignment feature of the prosthetic foot reduced the effect of a change in footwear on kinematics, and permitted walking in heeled shoes when it might otherwise not be possible. Persistence of some deviations suggests differences in walking task demand remained despite adjustment.Implications for rehabilitationPermitting prosthesis users to don footwear of choice may improve body image, well-being and quality of life following amputation.Prosthetic feet that permit user ankle adjustment can reduce gait deviations associated with a change in footwear heel height, although kinematic adaptations are individual.

Biomechanical evaluation over level ground walking of user-specific prosthetic feet designed using the lower leg trajectory error framework.

The walking pattern and comfort of a person with lower limb amputation are determined by the prosthetic foot's diverse set of mechanical characteristics. However, most design methodologies are iterative and focus on individual parameters, preventing a holistic design of prosthetic feet for a user's body size and walking preferences. Here we refined and evaluated the lower leg trajectory error (LLTE) framework, a novel quantitative and predictive design methodology that optimizes the mechanical function of a user's prosthesis to encourage gait dynamics that match their body size and desired walking pattern. Five people with unilateral below-knee amputation walked over-ground at self-selected speeds using an LLTE-optimized foot made of Nylon 6/6, their daily-use foot, and a standardized commercial energy storage and return (ESR) foot. Using the LLTE feet, target able-bodied kinematics and kinetics were replicated to within 5.2% and 13.9%, respectively, 13.5% closer than with the commercial ESR foot. Additionally, energy return and center of mass propulsion work were 46% and 34% greater compared to the other two prostheses, which could lead to reduced walking effort. Similarly, peak limb loading and flexion moment on the intact leg were reduced by an average of 13.1%, lowering risk of long-term injuries. LLTE-feet were preferred over the commercial ESR foot across all users and preferred over the daily-use feet by two participants. These results suggest that the LLTE framework could be used to design customized, high performance ESR prostheses using low-cost Nylon 6/6 material. More studies with large sample size are warranted for further verification.

Comparison of Ischial Containment and Subischial Sockets Effect on Gait Biomechanics in People With Transfemoral Amputation: A Randomized Crossover Trial.

OBJECTIVE: To compare gait biomechanics of the Northwestern University Flexible Sub-Ischial Vacuum (NU-FlexSIV) Socket to the ischial containment (IC) socket. DESIGN: Randomized crossover trial with 2, 7-week periods. SETTING: Private prosthetic clinics and university research laboratory. PARTICIPANTS: A total of 30 enrolled (n=30); 25 participants completed the study with full (n=18) or partial data (n=7). INTERVENTIONS: Two custom-fabricated sockets (IC and NU-FlexSIV), worn full-time for 7 weeks, with testing at 1, 4, and 7 weeks after socket delivery. MAIN OUTCOME MEASURES: Gait analyses were conducted at 1, 4, and 7 weeks post socket delivery. Differences between sockets in selected gait variables related to hip motion and coronal plane socket stability were assessed. RESULTS: For participants with data for both sockets at week 7 (n=19), there were no significant differences in any gait variables between sockets at self-selected normal walking speed. However, when all participants and all study time points were assessed (n=25), there was a significant main effect of socket (P=.013), with prosthetic side sagittal plane hip range of motion being significantly greater for the NU-FlexSIV Socket at self-selected normal walking speed. There were no other significant effects. CONCLUSIONS: The results suggest that, compared to the IC socket, the NU-FlexSIV Socket did not alter gait biomechanics related to hip motion and coronal plane socket stability in people with unilateral transfemoral amputation.

Effects of walking speed and prosthetic knee control type on external mechanical work in transfemoral prosthesis users.

During human locomotion, each limb performs step-to-step work on the body center of mass to maintain forward walking. This energy exchange relies on physiological mechanisms which are altered or impaired in transfemoral prosthesis users (TFPUs). Exploring step-to-step energy exchange modifications displayed by TFPUs at greater walking speeds may provide insight into their means for improving gait efficiency. The primary aim of this study was to characterize the effects of walking speed on mechanical work in unilateral TFPUs. The secondary aim assessed the effect of prosthetic knee (microprocessor, mechanical passive) on limb collision work. Twenty-five TFPUs walked with their customary prosthesis on a split-belt instrumented treadmill at eight speeds (0.55-1.53 m/s range), and collision, midstance, and push-off work were calculated for each limb. TFPUs displayed a significant (p < 0.001) bilateral increase in collision work with increased walking speed, but midstance and push-off work increased only for the sound limb and remained nearly constant for the prosthetic limb. TFPUs displayed significantly (p < 0.001) less push-off work generated by the prosthetic limb across all speeds. A microprocessor knee was associated with reduced sound limb collision work across speeds with the peak (negative) power being significantly greater for mechanical knees (p = 0.032). Results suggest that TFPU gait inefficiency may be related to a near complete loss of energy transfer on the prosthetic limb, relying on the sound limb to drive energy changes. Such reliance emphasizes need for attention to the long-term effects on sound limb health and possible benefit of microprocessor knees to offset that impact.

Effects of women's footwear on the mechanical function of heel-height accommodating prosthetic feet.

The loaded mechanical function of transtibial prostheses that result from the clinical assembly, tuning, and alignment of modular prosthetic components can directly influence an end user's biomechanics and overall mobility. Footwear is known to affect prosthesis mechanical properties, and while the options of footwear are limited for most commercial feet due to their fixed geometry, there exists a selection of commercial prosthetic feet that can accommodate a moderate rise in heel height. These feet are particularly relevant to women prosthesis users who often desire to don footwear spanning a range of heel heights. The aim of this study was to assess the effects of adding women's footwear (flat, trainer, 5.08 cm heel) on the mechanical properties (deformation and energy efficiency) of four models of heel-height accommodating prosthetic feet. Properties were measured through loading-unloading at simulated initial contact, midstance and terminal stance orientations with a universal materials test system, and statistically compared to a barefoot condition. Results suggest that the addition of footwear can alter the level of foot deformation under load, which may be a function of the shoe and alignment. Moreover, while each foot displayed different amounts of energy storage and return, the addition of footwear yielded similar levels of energy efficiency across foot models. Overall, prosthesis users who don shoes of varying heel heights onto adjustable prosthetic feet and their treating clinicians should be aware of the potential changes in mechanical function that could affect the user experience.

Reducing stiffness of shock-absorbing pylon amplifies prosthesis energy loss and redistributes joint mechanical work during walking.

BACKGROUND: A shock-absorbing pylon (SAP) is a modular prosthetic component designed to attenuate impact forces, which unlike traditional pylons that are rigid, can compress to absorb, return, or dissipate energy. Previous studies found that walking with a SAP improved lower-limb prosthesis users' comfort and residual limb pain. While longitudinal stiffness of a SAP has been shown to affect gait kinematics, kinetics, and work done by the entire lower limb, the energetic contributions from the prosthesis and the intact joints have not been examined. The purpose of this study was to determine the effects of SAP stiffness and walking speed on the mechanical work contributions of the prosthesis (i.e., all components distal to socket), knee, and hip in individuals with a transtibial amputation. METHODS: Twelve participants with unilateral transtibial amputation walked overground at their customary (1.22 ± 0.18 ms-1) and fast speeds (1.53 ± 0.29 ms-1) under four different levels of SAP stiffness. Power and mechanical work profiles of the leg joints and components distal to the socket were quantified. The effects of SAP stiffness and walking speed on positive and negative work were analyzed using two-factor (stiffness and speed) repeated-measure ANOVAs (α = 0.05). RESULTS: Faster walking significantly increased mechanical work from the SAP-integrated prosthesis (p < 0.001). Reducing SAP stiffness increased the magnitude of prosthesis negative work (energy absorption) during early stance (p = 0.045) by as much as 0.027 Jkg-1, without affecting the positive work (energy return) during late stance (p = 0.159), suggesting a damping effect. This energy loss was partially offset by an increase in residual hip positive work (as much as 0.012 Jkg-1) during late stance (p = 0.045). Reducing SAP stiffness also reduced the magnitude of negative work on the contralateral sound limb during early stance by 11-17% (p = 0.001). CONCLUSIONS: Reducing SAP stiffness and faster walking amplified the prostheses damping effect, which redistributed the mechanical work, both in magnitude and timing, within the residual joints and sound limb. With its capacity to absorb and dissipate energy, future studies are warranted to determine whether SAPs can provide additional user benefit for locomotor tasks that require greater attenuation of impact forces (e.g., load carriage) or energy dissipation (e.g., downhill walking).

Focusing research efforts on the unique needs of women prosthesis users.

INTRODUCTION: Women with lower limb loss represent a relevant and growing patient cohort with unique rehabilitation needs. These needs are emphasized in a growing body of literature and the most recent Veteran Affairs/Department of Defense clinical practice guidelines. PROSTHETICS CHALLENGES: Women with limb loss experience greater dissatisfaction with prosthetic fit, appearance, and types of footwear they can use. There is a lack of prosthetics solutions to accommodate the desire of women to wear different footwear varieties, including high heels. The choice to wear a variety of footwear is important to attire and hence community participation. Despite these recognized challenges, women are still underserved in prosthetics research, which limits available information to guide the rehabilitation process. RESEARCH INITIATIVES: This narrative review describes considerations of lower limb prosthesis prescription and use by women, and examples of current research to address these topics. Research efforts are beginning to explore factors that contribute to prosthetics prescription for women, and design creative prosthetics solutions to expand the range of available footwear options. Research is still needed to characterize the types of footwear women with limb loss prefer to use, and the effects of prosthesis designs, footwear, and lower limb loss on women mobility outcomes and community participation. CONCLUSIONS: Through targeted research initiatives, scientists and clinicians can be responsive to the specific needs of women to provide evidence-based guidelines for prosthetics prescription and improve the patient-centered care after limb loss.

Knee Swing Phase Flexion Resistance Affects Several Key Features of Leg Swing Important to Safe Transfemoral Prosthetic Gait.

We systematically investigate in-vivo the effect of increasing prosthetic knee flexion damping on key features of the swing phase of individuals with transfemoral amputation during walking. Five experienced prosthesis users walked using a prototype device in a motion capture laboratory. A range of interchangeable hydraulic rotary dampers was used to progressively modify swing phase flexion resistance in isolation. Toe clearance (TC; vertical distance toe to floor), effective leg length (ELL; distance hip to toe), and knee flexion angle during swing phase were computed, alongside the sensitivities of vertical toe position to angular displacements at the hip, knee and ankle. Key features of these profiles were compared across 5 damping conditions. With higher damping, knee extension occurred earlier in swing phase, promoting greater symmetry. However, with implications for toe catch, minimum TC reduced, and minimum TC and maximum ELL occurred earlier; temporally closer to mid-swing, when the limb must pass the stance limb. Further, TC became less sensitive to changes in hip flexion, suggesting a lesser ability to control toe clearance without employing proximal or contralateral compensations. There is a trade-off between key features related to gait safety when selecting an appropriate resistance for a mechanical prosthetic knee. In addition to highlighting broader implications surrounding swing phase damping selection for the optimization of mechanical knees, this work reveals design considerations that may be of utility in the formulation of control strategies for computerized devices.

Inter-limb weight transfer strategy during walking after unilateral transfemoral amputation.

Although weight transfer is an important component of gait rehabilitation, the biomechanical strategy underlying the vertical ground reaction force loading/unloading in individuals with unilateral transfemoral amputation between intact and prosthetic limbs remains unclear. We investigated weight transfer between limbs at different walking speeds in 15 individuals with unilateral transfemoral amputation and 15 individuals without amputation as controls, who walked on an instrumented treadmill. The normalized unloading and loading rates were calculated as the slope of decay and rise phase of the vertical ground reaction force, respectively. We performed linear regression analyses for trailing limb's unloading rate and leading limb's loading rate between the prosthetic, intact, and control limbs. While loading rate increased with walking speed in all three limbs, the greatest increase was observed in the intact limb. In contrast to the other limbs, the prosthetic limb unloading rate was relatively insensitive to speed changes. Consequently, the regression line between trailing prosthetic and leading intact limbs deviated from other relationships. These results suggest that weight transfer is varied whether the leading or trailing limb is the prosthetic or intact side, and the loading rate of the leading limb is partially affected by the unloading rate of the contralateral trailing limb.