Mechanical work performed by individual limbs of transfemoral amputees during step-to-step transitions: Effect of walking velocity

The greater metabolic demand during the gait of people with a transfemoral amputation limits their autonomy and walking velocity. Major modifications of the kinematic and kinetic patterns of transfemoral amputee gait quantified using gait analysis may explain their greater energy cost. Donelan et al. proposed a method called the individual limb method to explore the relationships between the gait biomechanics and metabolic cost. In the present study, we applied this method to quantify mechanical work performed by the affected and intact limbs of transfemoral amputees. We compared a cohort of six active unilateral transfemoral amputees to a control group of six asymptomatic subjects. Compared to the control group, we found that there was significantly less mechanical work produced by the affected leg and significantly more work performed by the unaffected leg during the step-to-step transition. We also found that this mechanical work increased with walking velocity; the increase was less pronounced for the affected leg and substantial for the unaffected leg. Finally, we observed that the lesser work produced by the affected leg was linked to the increase in the hip flexion moment during the late stance phase, which is necessary for initiating knee flexion in the affected leg. It is possible to quantify the mechanical work performed during gait by people with a transfemoral amputation, using the individual limb method and conventional gait laboratory equipment. The method provides information that is useful for prosthetic fitting and rehabilitation

Finite element modelling of an energy–storing prosthetic foot during the stance phase of transtibial amputee gait

Energy-storing prosthetic feet are designed to store energy during mid-stance motion and to recover it during latestance motion. Gait analysis is the most commonly used method to characterize prosthetic foot behaviour during walking. In using this method, however, the foot is generally modelled as a rigid body. Therefore, it does not take into account the ability of the foot to deform. However, the way this deformation occurs is a key parameter of various foot properties under gait conditions. The purpose of this study is to combine finite element modelling and gait analysis in order to calculate the strain, stress and energy stored in the foot along the stance phase for self-selected and fast walking speeds. A finite element model, validated using mechanical testing, is used with boundary conditions collected experimentally from the gait analysis of a single transtibial amputee. The stress, strain and energy stored in the foot are assessed throughout the stance phase for two walking speed conditions: a self-selected walking speed (SSWS), and a fast walking speed (FWS). The first maximum in the strain energy occurs during heel loading and reaches 3 J for SSWS and 7 J for FWS at the end of the first double support phase. The second maximum appears at the end of the single support phase, reaching 15 J for SSWS and 18 J for FWS. Finite element modelling combined with gait analysis allows the calculation of parameters that are not obtainable using gait analysis alone. This modelling can be used in the process of prosthetic feet design to assess the behaviour of a prosthetic foot under specific gait conditions

Vaulting quantification during level walking of transfemoral amputees

Background: Vaulting is a gait compensatory mechanism used by transfemoral amputees to assist toe clearance during the prosthetic swing phase. It is defined by a plantar flexion of the contralateral ankle during the single-limb support phase. The aim of the study is to propose a method to quantify vaulting of transfemoral amputees. Methods: 17 transfemoral amputees and 28 asymptomatic subjects participated in the data collection. Kinematics and kinetics of thewhole bodywere recordedwhile subjectswerewalking on a level surface. Biomechanical gait analysis was focused on a reduced set of parameters linked to the contralateral ankle, the contralateral knee and the trajectory of the center of pressure. The patients were classified in two groups: with orwithout vaulting using video recordings. Differences between both groups and the control group were analyzed. Findings: A higher generated ankle powerwas found during the single support phase of the contralateral limb of transfemoralamputees presenting vaulting. These subjects presented also a higher dissipated knee flexion power before the peak in ankle flexion power. The trajectory of the center of pressurewas also modified by the vaulting. Interpretation: Vaulting for transfemoral amputees is characterized by a propulsive plantar flexion at the contralateral ankle. Quantifying the ankle flexion power during the contralateral single support phase will help in understanding vaulting.This study was supported by the French National Research Agency, under reference ANR-2010-TECS-020. The authors are deeply grateful to F. Lavaste, N. Martinet, J. Paysant, and N. Rapin for their contribution to the study

Influence of physical capacities of males with transtibial amputation on gait adjustments on sloped surfaces

The aim of the study was to investigate how kinematic and kinetic adjustments between level and slope locomotion of persons with transtibial amputation are related to their individual muscular and functional capacities. A quantified gait analysis was conducted on flat and slope surfaces for seven patients with transtibial amputation and a control group of eight subjects to obtain biomechanical parameters. In addition, maximal isometric muscular strength (knee and hip extensors) and functional scores were measured. The results of this study showed that most of the persons with transtibial amputation could adapt to ramp ascent either by increasing ankle, knee, and hip flexion angles of the residual limb and/or by recruiting their hip extensors to guarantee enough hip extension power during early stance. Besides, 6-minute walk test score was shown to be a good predictor of adaptation capacities to slope ascent. In ramp descent, the increase of knee flexion moment was correlated with knee extensor strength and residual-limb length. However, no correlation was observed with functional parameters. Results show that the walking strategy adopted by persons with transtibial amputation to negotiate ramp locomotion mainly depends on their muscular capacities. Therefore, muscular strengthening should be a priority during rehabilitation.This material was based on work supported by the French National Research Agency (grant ANR-2010-TECS-020)

On the influence of the shoulder kinematic chain on joint kinematics and musculotendon lengths during wheelchair propulsion estimated from multibody kinematics optimization

Multibody kinematic optimization is frequently used to assess shoulder kinematics during manual wheelchair (MWC) propulsion but multiple kinematics chains are available. It is hypothesized that these different kinematic chains affect marker tracking, shoulder kinematics and resulting musculotendon (MT) lengths. In this study, shoulder kinematics and MT lengths obtained from four shoulder kinematic chains (open-loop thorax-clavicle-scapula-humerus (M1), closed-loop with contact ellipsoid (M2), scapula rhythm from regression equations (M3), and a single ball-and- socket joint between the thorax and the humerus (M4) were compared. Right-side shoulder kinematics from seven subjects were obtained with 34 reflective markers and a scapula locator using an optoelectronic motion capture system while propelling on a MWC simulator. Data was processed based on the four models. Results showed the impact of shoulder kinematic chains on all studied variables. Marker reconstruction errors were found similar between M1 and M2 and lower than for M3 and M4. Few degrees of freedom (DoF) were noticeably different between M1 and M2, but all shoulder DoFs were significantly affected between M1 and M4. As a consequence of differences in joint kinematics, MT lengths were affected by the kinematic chain definition. The contact ellipsoid (M2) was found as a good trade-off between marker tracking and penetration avoidance of the scapula. The regression-based model (M3) was less efficient due to limited humerus elevation during MWC propulsion, as well as the ball-and-socket model (M4) which appeared not suitable for upper limbs activities, including MWC propulsion.This study has been self-funded by the Centre d'Etude et de Recherche sur l'Appareillage des Handicapés (Institution Nationale des Invalides), Créteil, France

Whole limb push-off work in people with transtibial amputation during slope ascent

Unilateral transtibial amputation impairs locomotion, especially in daily living outdoor situations. As an example, slope ascent requires specific gait adjustments such as hip power generation during single support followed by ankle power generation during second double support. Hip extensor strengthening could help peo- ple with transtibial amputation for hip propulsion in slope ascent (Langlois et al. 2014). Energy storage and return (ESAR) foot-ankle prostheses have been designed to absorb and release elastic energy in an attempt to restore some functions of the amputated limb. However, it remains unclear how ESAR feet contribute to center of mass propulsion, especially during slope ascent. Simple models were recently developed to globally analyze gait in an energetic point of view by computing the center of mass mechanical work (Donelan et al. 2002; Kuo et al. 2005). Particularly, several hypoth- eses permit to estimate for each lower limb the whole limb push-off work during double support (Kuo et al. 2005). Using this approach, step-to-step transition was investigated during level walking, in able- bodied subjects wearing prosthetic foot (Caputo & Collins 2014) and in people with transtibial and transfemoral amputation (Houdijk et al. 2009; Bonnet et al. 2014), and in slopes in able-bodied subjects (Franz et al. 2012). Up to now, no study quantified prosthetic and contralateral push-off work during slope ascent in a below-knee amputee population. Thus, the aim of the study is to investigate center of mass mechanical work adjustments during the propulsion period during slope ascent for two inclinations of slopes compared to level walking in people with transtibial amputation

Evolution of vaulting strategy during locomotion of individuals with transfemoral amputation on slopes and cross-slopes compared to level walking

Background: Vaulting is a walking strategy qualitatively characterized in clinics by the sound ankle plantiflexion in midstance to assist prosthetic foot clearance. Even though potentially harmful, this strategy is often observed among people with transfemoral amputation to secure clearance of the prosthetic limb during swing phase. The aim of the study is to provide a quantitative analysis of the evolution of the vaulting strategy in challenging situations of daily living. Methods: 17 persons with transfemoral amputation and 17 able-bodied people participated in the study. Kinematic and kinetic gait analyses were performed for level walking, 10% inclined cross-slope walking, 5% and 12% inclined slope ascending. To study vaulting strategy, peak of generated power at the sound ankle at midstance was identified and quantified in the different walking situations. In particular, values were compared to a vaulting threshold corresponding to a peak of generated power superior to 0.15 W/kg. Findings: The vaulting threshold was exceeded for a larger proportion of people with amputation during crossslope locomotion and slope ascent than during level walking. In addition, magnitude of the peak of generated power increased significantly compared to level walking in these situations. Interpretation: Vaulting seems to be widely used by patients with transfemoral amputation in daily living situations. The number of patients using vaulting increased with the difficulty of the walking situation. Results also suggested that patients could dose the amount of vaulting according to gait environment to secure prosthetic toe clearance. During rehabilitation, vaulting should also be corrected or prevented in daily living tasks

Changes in Wheelchair Biomechanics Within the First 120 Minutes of Practice: Spatiotemporal Parameters, Handrim Forces, Motor Force, Rolling Resistance and Fore-Aft Stability

Purpose: During manual wheelchair (MWC) skill acquisition, users adapt their propulsion technique through changes in biomechanical parameters. This evolution is assumed to be driven towards a more efficient behavior. However, when no specific training protocol is provided to users, little is known about how they spontaneously adapt during overground MWC locomotion. For that purpose, we investigated this biomechanical spontaneous adaptation within the initial phase of low-intensity uninstructed training. Materials and methods: Eighteen novice able-bodied subjects were enrolled to perform 120min of unin- structed practice with a field MWC, distributed over 4 weeks. Subjects were tested during the very first minutes of the program, and after completion of the entire training protocol. Spatiotemporal parameters, handrim forces, motor force, rolling resistance and fore-aft stability were investigated using an instru- mented field wheelchair. Results: Participants rapidly increased linear velocity of the MWC, thanks to a higher propulsive force. This was achieved thanks to higher handrim forces, combined with an improved fraction of effective force for startup but not for propulsion. Despite changes in mechanical actions exerted by the user on the MWC, rolling resistance remained constant but the stability index was noticeably altered. Conclusion: Even if no indication is given, novice MWC users rapidly change their propulsion technique and increase their linear speed. Such improvements in MWC mobility are allowed by a mastering of the whole range of stability offered by the MWC, which raises the issue of safety on the MWC

Cluster analysis to investigate biomechanical changes during learning of manual wheelchair locomotion: a preliminary study

No abstract availabl

Comparison of shoulder kinematic chain models and their influence on kinematics and kinetics in the study of manual wheelchair propulsion

Several kinematic chains of the upper limbs have been designed in musculoskeletal models to investi- gate various upper extremity activities, including manual wheelchair propulsion. The aim of our study was to compare the effect of an ellipsoid mobilizer formulation to describe the motion of the scapu- lothoracic joint with respect to regression-based models on shoulder kinematics, shoulder kinetics and computational time, during manual wheelchair propulsion activities. Ten subjects, familiar with manual wheelchair propulsion, were equipped with reflective markers and performed start-up and propulsion cycles with an instrumented field wheelchair. Kinematic data obtained from the optoelectronic system and kinetic data measured by the sensors on the wheelchair were processed using the OpenSim software with three shoulder joint modeling versions (ellipsoid mobilizer, regression equations or fixed scapula) of an upper-limb musculoskeletal model. As expected, the results obtained with the three versions of the model varied, for both segment kinematics and shoulder kinetics. With respect to the model based on regression equations, the model describing the scapulothoracic joint as an ellipsoid could capture the kinematics of the upper limbs with higher fidelity. In addition, the mobilizer formulation allowed to com- pute consistent shoulder moments at a low computer processing cost. Further developments should be made to allow a subject-specific definition of the kinematic chain