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Uneven ground, slopes, stairs, sidewalks are constraining situations that must be overcome by transfemoral amputees (TFA). However, most of prosthetic systems do not have ankle mobility, the connection between the prosthetic knee and the prosthetic foot being a rigid part. A certain flexibility is allowed by the energy storage restitution feet thanks to their stiffness. But they do not allow a complete adaptation to daily encountered walking situations, like walking on slopes (ascent and descent) or downstairs [1]. Furthermore, TFA have a high risk of falling, with more than 50% of them reporting falling at least once in a year [2]. This risk is increased by the lack of musculature due to the amputation and the lack of mobility of the prosthetic ankle during the swing phase [3]. The aim of this study was to evaluate whether a microprocessor-controlled knee-ankle system (MPK_NEW) can help improve walking in transfemoral amputees. Eleven TFA with an activity level of d4602 (International Classification of Function, Disability and Health) or higher and wearing a microprocessor knee able to control stance and swing phases (MPK_HAB), for at least 3 months, were included in this study. They wore both prostheses (MPK_HAB and MPK_NEW) for 4 weeks, starting randomly with one or the other. At the end of each period, a quantified gait analysis (level ground, 12% slopes ascent and descent, downstairs) was performed using VICON® optoelectronic system (Vicon Motion Systems, Oxford Metrics, UK, sampling at 100 Hz) with 54 full-body markers-set. Flat Foot Time (FFT, where the ankle angle in the sagittal plane was within ± 1.25° of its orientation at 20% of the gait cycle) and Minimum Toe Clearance (MTC, minimum distance between the foot and the ground during the swing phase) were calculated for both prostheses. Student or Wilcoxon test were performed to assess significance at 0.05. Fig. 1 A shows an increase in flat-foot time for all walking situations with the MPK_NEW prosthesis, which was significant (*,p_value < 0.01) for all situations but the slope ascent one. Fig. 1B shows a significant increase in MTC (*, p_value < 0.01) when walking at level ground and ascent slope with the MPK_NEW prosthesis. Fig. 1. Comparison of FFT and MTC for each prosthesis in different walking situations [Display omitted] The knee-ankle synergy allows plantar and dorsal flexion during the stance and swing phases, increasing FFT (stance stability) and MTC (swing phase security) in various daily situations. This was consistent with the literature observed on transtibial amputees and approaching the behavior of asymptomatic subjects [4–6]. Thus, this new prosthetic system may improve stability and security for TFA [4,7], allowing them to better adapt to their daily environment. [ABSTRACT FROM AUTHOR]

Background: The analysis of biomechanical parameters derived from the body center of mass (BCoM) 3D motion allows for the characterization of gait impairments in people with lower-limb amputation, assisting in their rehabilitation. In this context, magneto-inertial measurement units are promising as they allow to measure the motion of body segments, and therefore potentially of the BCoM, directly in the field. Finding a compromise between the accuracy of computed parameters and the number of required sensors is paramount to transfer this technology in clinical routine.Research Question: Is there a reduced subset of instrumented segments (BSN) allowing a reliable and accurate estimation of the 3D BCoM acceleration transfemoral amputees?Methods: The contribution of each body segment to the BCoM acceleration was quantified in terms of weight and similarity in ten people with transfemoral amputation. First, body segments and BCoM accelerations were obtained using an optoelectronic system and a full-body inertial model. Based on these findings, different scenarios were explored where the use of one sensor at pelvis/trunk level and of different networks of segment-mounted sensors for the BCoM acceleration estimation was simulated and assessed against force plate-based reference acceleration.Results: Trunk, pelvis and lower-limb segments are the main contributors to the BCoM acceleration in transfemoral amputees. The trunk and shanks BSN allows for an accurate estimation of the sagittal BCoM acceleration (Normalized RMSE ≤ 13.1 %, Pearson's correlations r ≥ 0.86), while five segments are necessary when the 3D BCoM acceleration is targeted (Normalized RMSE ≤ 13.2 %, Pearson's correlations r ≥ 0.91).Significance: A network of three-to-five segments (trunk and lower limbs) allows for an accurate estimation of 2D and 3D BCoM accelerations. The use of a single pelvis- or trunk-mounted sensor does not seem advisable. Future studies should be performed to confirm these results where inertial sensor measured accelerations are considered. [ABSTRACT FROM AUTHOR]

Objective Manual wheelchair (MWC) allows active disabled people to recover mobility but constrains both cardiorespiratory and upper-limb musculoskeletal systems. User morphology, experience and propulsion strategy as well as environment and wheelchair settings can affect the constraints sustained by the upper limbs. Choosing and configuring a wheelchair is a difficult task, which requires the analysis of multiple factors. Due to this difficulty, the process sometimes results in non-optimized wheelchair settings. The present work describes a method which simulates the wheelchair behavior from a mechanical model. The ability of this method to provide a better understanding of the effect of various wheelchair settings on propulsion difficulty is illustrated through an example. Material/patients and methods At first, appropriate representations (or “models”) need to be developed. In this study, the user was modeled by his center of mass position with respect to drive wheels; the MWC was modeled by an assembly of solids characterized by their weight, geometry and material; and the environment was modeled by a flat surface characterized by roughness and inclination. Through mechanical analysis, the MWC settings and movements were linked to the user efforts and energy losses. As inputs for the simulation, the efforts applied by one subject were previously measured during straightforward propulsion using specific instrumented MWC. Finally, various propulsion scenarios were numerically simulated, in which wheelchair settings were changed, keeping every other experimental conditions constant. Scenarios where instability occurred were discarted. Results Simulation allowed defining an appropriate wheelchair configuration (mainly defined by a backward position of the user and large castor radii) where energy losses were decreased by 2.5 times with respect to the 3.3 Joules per propulsion cycle observed during experiments. Discussion – conclusion When choosing and configuring a wheelchair, tradeoffs often need to be found between energetic performance and other mandatory aspects, like stability. Through numerical simulation, optimization can be developed to assist in defining a set of MWC setting that takes into account the necessary tradeoffs. Nowadays, similar analysis can be applied to hard smooth/carpet surfaces, turning motion, ramps and cross slopes. More complex subject-specific musculoskeletal models are developed for better precision and understanding. [ABSTRACT FROM AUTHOR]

• The scapulothoracic ellipsoid mobilizer is promising for wheelchair biomechanics. • The ellipsoid-based model allows an improved kinematic reconstruction. • The ellipsoid-based and regression-based models display similar shoulder moments. • The ellipsoid-based model decreases the computational time. Several kinematic chains of the upper limbs have been designed in musculoskeletal models to investigate 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 scapulothoracic 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 compute consistent shoulder moments at a low computer processing cost. Further developments should be made to allow a subject-specific definition of the kinematic chain. [ABSTRACT FROM AUTHOR]

Objective Manual wheelchair (MWC) is a constraining form of locomotion for the musculoskeletal system and many MWC users are concerned by musculoskeletal disorders (MSD). Detecting and quantifying MWC related activities are of high interest for the day-to-day follow-up of patients using a MWC as a primary mode of locomotion. Indeed, it could assist clinician in early identification of MSD occurrence or optimizing the user environment (furnishing arrangements, etc). Since few years, several tools combining sensors and data processing algorithms were developed. However, the validation of these tools is difficult, in particular because video analysis used as a reference is both highly time consuming and sometimes inaccurate due to the cameras field of view. Hence, there is a need of an alternative reference method to facilitate the validation of such tools. As an alternative to video analysis, we propose to use an instrumented MWC, initially dedicated for investigating MWC biomechanics, as a new reference method for tasks identifications. Material/patients and methods This MWC was equipped with handrim dynamometers to measure handrim forces and two angular potentiometers fixed on rear wheels to determine the MWC trajectory. Data processing included data aggregation followed by multichannel symbolic representation based on force and velocity thresholds. Currently, the method was implemented for flat horizontal displacement and allowed distinguishing resting: start-up, propulsion, braking and turning motion various curvature radii. The method was tested on 18 able-bodied subjects during actual displacements. Results Results show that for most subjects, the method allowed identifying start-up, propulsion, braking and turning motion tasks. However, a specific adaptation of some thresholds was required for 2 subjects. Since the first subject kept his hands on the handrims during the recovery phase, making difficult the separation of the different tasks and the other subject used a desynchronized propulsion pattern between right and left upper-limbs (close to an alternative push strategy), which resulted in a failure of the identification of propulsion cycle. Discussion, conclusion Even if a real validation of this method against video analysis is still required, the results of the method are encouraging. Some works are still needed to include displacements on more various inclined surfaces and uneven terrain. [ABSTRACT FROM AUTHOR]

Objective Pressure insoles are developed to be placed in the shoes and provide embedded measurement of the pressure or/and normal ground reaction forces (NGrF). Recently, Pedoped ® insoles were commercialized and consists in only one sensor providing NGrF in real-time biofeedback. As NGrF represents about 90% of ground reaction forces during gait, this device permits to record the lower limb loading during walking, standing or in other daily living activities. Thus, these insoles could be a useful tool in rehabilitation when dealing with gait asymmetry or load recovery. As the first step to evaluate the reliability of these insoles, the accuracy of NGrF measurement with Pedoped ® insoles was assessed during gait of healthy subjects. Material/patients and methods Five healthy subjects were recruited. All subjects were wearing the same shoes with Pedoped ® insoles placed inside. Data collection was carried out in a motion capture laboratory equipped with 4 AMTI ® force platforms (PFF). Subjects were asked to stamp each foot on a PFF during one minute at self-selected speed. PFF and insoles data were synchronized by detecting the first NGrF above 20 N for the two systems. About sixty cycles were considered per insole to compare NGrF to PFF measurements. The mean error on NGrF over all cycles and insoles was computed and normalized by the maximum NGrF. Bland-Altman plots, RMSE and NRMSE, as well as Pearson correlation coefficient were computed. Results A mean error on NGrF of 31.7 N (SD: 31.9 N) was obtained between insoles and PFF. It corresponds to 3.6% (± 3.7%) of maximum NGrF during stamping. RMSE and NRMSE were of 45.4 N and 5.2% respectively. A 0.99 correlation coefficient was obtained. Bland-Altman plots highlighted that the higher the NGrF the higher the error. Discussion, conclusion Results suggested that the insoles are reliable compared to force platforms. However, highest errors seemed to be associated to calibration issues. Thus, more works must be conducted to evaluate their reliability in long time use, to estimate the intra and interoperator error, and to set up a validated protocol with injured patients. However the biofeedback of NGrF in real time with these embedded sensors open perspectives in rehabilitation. [ABSTRACT FROM AUTHOR]

Objective Even if properly fitted, the posture and gait of amputee people are disturbed, leading to compensations and over-solicitations of the contralateral limb. The recent commercialization of new generation ankle-foot (NG) prosthesis is not covered by French social security insurance. The evaluation of the service delivered by these medical devices was until now a combination of multidisciplinary evaluations and patient assessments, but needs objective evaluation. Several teams reported a benefit of NG feet, mainly in terms of joint mobility, walking speed and reduction in compensations. But the main subjective improvement is in balance, both in static (more comfortable waiting position) as well as in dynamic (quality and fluidity of walking), which was poorly evaluated in amputees with NG feet. The main objective of this research is to evaluate the relevance of these NG feet in terms of static stability, on both flat and inclined surfaces. Material/patients and methods Six transtibial subjects were included. Three NG feet (Elan ® , Propriofoot ® , Meridium ® ) and the patient's usual foot were successively tested. For each foot type, after socket and alignment validation by an expert prosthetist, an acclimatization period of 15 days at home was observed. After this period, clinical, instrumental (static acquisitions of 20 s on two force platforms, eyes open and closed, on flat ground and on 12% inclined slope uphill and downhill) and functional evaluations (Berg Balance Scale and Activity Specific Balance Scale) were performed. Participants observed a wash out period of 3 weeks with the usual foot before testing each NG foot. The static parameters collected were: lower limb joint angles, Center of Pressure (COP) variation, ground reaction forces (GRF), and functional scores. Results In static position, a larger prosthetic ankle dorsiflexion, less compensations of the amputed lower limb, better symmetry of the GRF and increase of CoP parameters (as length of trajectory and range) were found with NG feet, compared to ESR. Discussion, conclusion The absence of postural control leads to asymmetrical posture, leading to osteoarticular complications. Ankle mobility of NG feet may allow a better balance and improve destabilizations adaptations, above all on slope, and may reduce sound limb compensations. [ABSTRACT FROM AUTHOR]