Helene Pillet

• PhD
• Professor (Associate) at École nationale supérieure d'arts et métiers

Additive manufacturing revolutionized the production of personalized objects from 3D models across various industries, including medical, aerospace and automotive, primarily through the widely accessible material extrusion process. Despite additive manufacturing advantages, the parts fabricated using additive manufacturing often exhibit lower elast...

Background: Advances in prosthetic technology, especially microprocessor-controlled knees (MPKs), have helped enhance gait symmetry and reduce fall risks for individuals who have undergone transfemoral amputation. However, challenges remain in walking in constrained situations due to the limitations of passive prosthetic feet, lacking ankle mobilit...

Background A hip flexion contracture (HFC) results in an inability to extend the hip by reducing the ROM of the affected hip. The condition affects one in four patients with above-knee amputations on the amputation side. While HFC in other disorders is known to decrease hip ROM and increase pelvic tilt during gait, its impact on the gait of patient...

Background Transmission of loads between the prosthetic socket and the residual limb is critical for the comfort and walking ability of people with transfemoral amputation. This transmission is mainly determined by the socket tightening, muscle forces, and socket ischial support. However, numerical investigations of the amputated gait, using modeli...

Plantar flexors (PF) spasticity is known to poorly correlate with active dorsiflexion (DF) impairment throughout the swing phase of hemiparetic gait. Spastic Cocontraction, instead, stemming from descending pathways, potentially misdirect antagonist PF activity opposing DF during swing. Electromyographic (EMG) recordings, while unable to differenti...

Featured Application This study is a first step for real-time monitoring the risk of falls during gait. Abstract The goal of this study was to analyze instability during stepping at different speeds in young and older adults. To this aim, the anteroposterior and the mediolateral distances between the body center of mass (COM) and the minimum momen...

The goal of this study was to analyze the instability during stepping of young and older adults at fast and spontaneous speed. To this aim, the anteroposterior and the mediolateral distances between the body center of mass (COM) and the minimum moment axis (MMA) were computed. A total of 15 young adults (25y.o. [19-29]) and 15 older adults 68.7y.o....

The results of this study show that the vertical free moment at the center of pressure can be neglected without hindering the capacity of the MMA-BCOM to discriminate the two populations. This conclusion makes realistic the quantification of the parameter by combining transverse forces estimated from inertial measurement units and location of the c...

In this abstract we compared stepping instability using the distance between the BCOM and the MMA on old and young population at spontaneous and fast speed. Our results demonstrate that the distance tends to increase for older population at both cadences. This tendency is consistent with the higher instability of older adults during stepping and th...

Introduction: It was hypothesized that pelvic retroversion in Adult Spinal Deformity (ASD) can be related to an increased hip loading explaining the occurrence of hip-spine syndrome. Research question: How pelvic retroversion can modify acetabular orientation in ASD during walking? Methods: 89 primary ASD and 37 controls underwent 3D gait anal...

Background: X-linked hypophosphataemia causes bone deformities and gait abnormalities that tend to worsen with age in the absence of appropriate treatment. However, doctors do not currently use quantitative tools to characterize these symptoms and their possible interactions. Methods: Radiographs and 3D gait data from 43 non-surgical growing chi...

The analysis of intra-cycle velocity profile of manual wheelchair (MWC) users has been used to highlight the significant role of trunk inertia in propulsion biomechanics. Maximal wheelchair linear velocity has previously been observed to be reached after the release of the handrims both during sports activities and daily life propulsion. This paper...

After a transtibial amputation, the prosthetic foot aims at replacing the missing ankle joint. Due to alteration of proprioception and mobility, the static balance of amputees is challenging. The stiffness of most of the usual prosthetic feet cannot adapt according to the situation. Thus, the control of the user’s balance is closely related to the...

Objectives The characterization of the instability of gait is a current challenge of biomechanics. Indeed, risks of falling naturally result from the difficulty to control perturbations of the locomotion pattern. Hence, the assessment of a synthetic parameter able to quantify the instability in real time will be useful for the prevention of falls o...

Introduction The Single Leg Hop test (SLHT) is commonly performed to determine readiness to return to sport (RTS) after anterior cruciate ligament (ACL) injury and reconstruction [1]. Usually, the between-limb symmetry of hop distance is considered as a criterion to clear the athletes to RTS. However, athletes may pass this criterion despite ongoin...

Introduction Anterior cruciate ligament (ACL) rupture is one of the most recurrent knee injuries in soccer players [1]. Commonly, global performance measures like jumping/hopping distance or time to perform agility test and side-cutting manoeuvres are used as criteria to determine readiness to return to sport after ACL reconstruction (ACLR) [1]. Ho...

Some works have already studied human trajectories during spontaneous locomotion. However, this topic has not been thoroughly studied in the context of human-human interactions, especially during collaborative carriage tasks. Thus, this manuscript aims to provide a broad analysis of the kinematics of two subjects carrying a table. In the present st...

Impingement with surrounding tissues is a major cause of failure of anterior cruciate ligament reconstruction. However, the complexity of the knee kinematics and anatomical variations make it difficult to predict the occurrence of contact and the extent of the resulting damage. Here we hypothesise that a description of wear between the reconstructe...

An alternative method for solving constrained Multibody kinematics optimisation using a penalty method on constraints and a Levenberg-Marquardt algorithm is proposed. It is compared to an optimisation resolution with hard kinematic constraints. These methods are applied to two pairs of experiments and models. The penalty method was at least 20 time...

Purpose To assess dynamic postural alignment in ASD during walking using a subject-specific 3D approach. Methods 69 ASD (51 ± 20 years, 77%F) and 62 controls (34 ± 13 years, 62%F) underwent gait analysis along with full-body biplanar Xrays and filled HRQoL questionnaires. Spinopelvic and postural parameters were computed from 3D skeletal reconstru...

During manual wheelchair (MWC) locomotion, the user’s upper limbs are subject to heavy stresses and fatigue because the upper body is permanently engaged to propel the MWC. These stresses and fatigue vary according to the environmental barriers encountered outdoors along a given path. This study aimed at conducting a systematic review of the litera...

Table synthetizing studies, as well as their methods and results, investigating wheelchair biomechanics in environmental barriers. This table is one of the outcomes of a systematic review published in PloS One (10.1371/journal.pone.0269657).

The role of the above-knee socket is to ensure the load transfer via the coupling of residual limb-prosthesis with minimal discomfort and without damaging the soft tissues. Modelling is a potential tool to predict socket fit prior to manufacture. However, state-of-the-art models only include the femur in soft tissues submitted to static loads negle...

Background Pressure-induced tissue strain is one major pathway for Pressure Ulcer development and, especially, Deep Tissue Injury. Biomechanical investigation of the time-dependent stress–strain mechanical behaviour of skeletal muscle tissue is therefore essential. In the literature, a viscoelastic formulation is generally assumed for the experimen...

Background Physiologic aging is associated with loss of mobility, sarcopenia, skin atrophy and loss of elasticity. These factors contribute, in the elderly, to the occurrence of a pressure ulcer (PU). Brightness mode ultrasound (US) and shear wave elastography (SWE) have been proposed as a patient-specific, bedside, and predictive tool for PU. Howe...

Abstract as conference proceeding: https://doi.org/10.1080/10255842.2021.1978758

During manual wheelchair (MWC) locomotion, the user's upper limbs are subject to significant levels of stress and fatigue because the upper body is permanently engaged to propel the MWC and in all daily activities (van der Woude et al., 2001). This stress can lead to pain and wounds in the upper limbs which in turn may lead to difficulties in auton...

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,...

Persons with above-knee amputation have increased energy consumption and greater difficulty in negotiating uphill and downhill slopes. Walking on slopes requires an adaptation of the positive and negative work performed by the joints of the lower limb to propel the center of mass. Modern prosthetic feet and knees can only partially adapt to changes...

The kinematics of the body center of mass (bCoM) may provide crucial information supporting the rehabilitation process of people with transfemoral amputation. The use of magneto-inertial measurement units (MIMUs) is promising as it may allow in-the-field bCoM motion monitoring. Indeed, bCoM acceleration might be obtained by fusing the estimated acc...

Background Body Center Of Mass velocity assessment is a prerequisite for several applications in prosthetic control and rehabilitation monitoring. Force plate data integration is a promising alternative to full-body quantitative analysis of segmental kinematics to estimate the velocity. Still, it remains to be implemented and validated for people w...

The proper management of the local mechanical environment within soft tissuesSoft tissue is a key challenge central the prevention ofPressure ulcer (PUs) Pressure Ulcers (PUs). Magnetic Resonance (MR) imaging is the preferred imaging modality to measure geometrical features associated with PUs. It is a very time-consuming method and it represents a...

The analysis of the body center of mass (BCoM) 3D kinematics provides insights on crucial aspects of locomotion, especially in populations with gait impairment such as people with amputation. In this paper, a wearable framework based on the use of different magneto-inertial measurement unit (MIMU) networks is proposed to obtain both BCoM accelerati...

Skin Marker (SM) based motion capture is the most widespread technique used for motion analysis. Yet, the accuracy is often hindered by Soft Tissue Artifact (STA). This is a major issue in clinical gait analysis where kinematic results are used for decision-making. It also has a considerable influence on the results of rigid body and Finite Element...

In case of transtibial amputation, the deficit resulting from the loss of the lower limb can be partly compensated with a prosthetic foot and adapted rehabilitation. New prosthetic feet have been developed for transtibial amputees to mimic ankle adaptability to varying terrain. Among them, Microprocessor Prosthetic Ankles (MPA) have a microprocesso...

Soft tissue deformation(STD) causes the most prominent source of error in skin marker (SM) based motion analysis, commonly referred to as Soft Tissue Artifact (STA). To compensate for its effect and to accurately assess in vivo joint kinematics, quantification of STD in three-dimension (3D) is essential. In the literature, different invasive and ra...

Subject-specific tensioning of ligaments is essential for the stability of the knee joint and represents a challenging aspect in the development of finite element models. We aimed to introduce and evaluate a new procedure for the quantification of ligament prestrains from biplanar X-ray and CT data. Subject-specific model evaluation was performed b...

Résumé Introduction Chez l’enfant ayant été traité pour un pied bot varus équin idiopathique (PBVE), le lien entre défauts morphologiques constatés cliniquement ou par radiographie standard et anomalies fonctionnelles est difficile à établir objectivement. Le but de ce travail est de démontrer la faisabilité d’une étude combinée par reconstruction...

Finite Element Analysis is a numerical modelling tool vastly employed in research facilities to analyse and predict load transmission between the human body and a medical device, such as a prosthesis or an exoskeleton. Yet, the use of FEM in a framework compatible with clinical constraints is hindered by, amongst others, heavy and time-consuming as...

Introduction In children treated for idiopathic equinovarus clubfoot (EVCF), the relation between morphologic defects on clinical examination and standard X-ray on the one hand and functional abnormalities on the other is difficult to objectify. The aim of the present study was to demonstrate the feasibility of combined 3D analysis of the foot and...

Featured Application This study could be useful when comparing the balance of standard and instrumented walking (e.g., elderly, prosthesis, exoskeleton) on uneven terrains. Moreover, it can be helpful in the field of motion generation of humanoid robotics. Abstract While multiple criteria to quantify gait instability exist, some limitations hinder...

Medical images are not typically included in protocol of motion laboratories. Thus, accurate scaling of musculoskeletal models from optoelectronic data are important for any biomechanical analysis. The aim of the current study was to identify a scaling method based on optoelectronic data, inspired from literature, which could offer the best trade-o...

In recent years, inertial measurement units (IMUs) have been proposed as an alternative to force platforms and pressure sensors for gait events (i.e., initial and final contacts) detection. While multiple algorithms have been developed, the impact of gait event timing errors on temporal parameters and asymmetry has never been investigated in people...

The present study combines low-dose bi planar X-rays with 3D motion capture to obtain a subject-specific 3D model of transfemoral amputated subjects and multibody kinematics optimization is used to obtain a prediction of the movement of the femur relative to the socket during gait.

The present study combines low-dose bi planar X-rays with 3D motion capture to obtain a subject-specific 3D model of transfemoral amputated subjects and multibody kinematics optimization is used to obtain a prediction of the movement of the femur relative to the socket during gait. https://sb2019-poitiers.sciencesconf.org/268598 DOI: 10.1080/102558...

Purpose: Daily locomotion with a manual wheelchair includes curvilinear movements. However, little is known about the resisting forces in play during turning manoeuvres where the wheels are generally both rolling and swivelling. This study aimed at quantifying the swivelling resistance parameters of several wheels on different surfaces and to evalu...

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 an...

Background: Internal soft tissue strains have been shown to be one of the main factors responsible for the onset of Pressure Ulcers and to be representative of its risk of development. However, the estimation of this parameter using Finite Element (FE) analysis in clinical setups is currently hindered by costly acquisition, reconstruction and comp...

Background: The compensations occurrence due to the alteration of the posture and the gait of persons with lower limb amputation is still an issue in prosthetic fitting. Recently, prosthetic feet designed to reproduce the physiological behaviour of the ankle using a microprocessor control have been commercialized to address this issue. Objectives:...

Purpose This study aims to describe the spinopelvic sagittal alignment in transfemoral amputees (TFAs) from a radiologic study of the spine with a postural approach to better understand the high prevalence of low back pain (LBP) in this population. Methods TFAs underwent X-rays with 3-D reconstructions of the full spine and pelvis. Sagittal parame...

In an effort to improve diagnostics and treatment of knee joint laxity and to minimize post-operative complications, development of patient-specific computational models of the knee joint is subject of current interest and investigation. A key strength of computational models is that they can provide an insight on the relative contributions of the...

Background Amputee gait is known to be asymmetrical, especially during loading of the lower limb. Monitoring asymmetry could be useful in quantifying patient performance during rehabilitation. Wearable insoles can provide normal ground reaction force asymmetry in real-life conditions. Objectives To characterize the validity of Loadsol ® insoles ve...

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...

The command of a microprocessor-controlled lower limb prosthesis classically relies on the gait mode recognition. Real time computation of the pose of the prosthesis (i.e., attitude and trajectory) is useful for the correct identification of these modes. In this paper, we present and evaluate an algorithm for the computation of the pose of a lower...

Microprocessor prosthetic knees, able to restore the gait of people with transfemoral amputation, are now often equipped with sensors embedded in the prosthetic shank, which could be used to assess some gait characteristics during real-life activities. In particular, an estimation of the walking speed during the locomotion of those subjects would b...

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 overgroun...

Adequate manual wheelchair (MWC) configuration is crucial for efficient MWC locomotion. Evaluating the effect of various configurations can be done through simulation, which relies on the definition of a mechanical model. The aim of this paper was to propose and evaluate a simplified mechanical model of a rolling and turning MWC. MWC decelerating m...

Manual wheelchair (MWC) locomotion is an exhausting task for the upper limbs. Hence, reducing energy loss can improve users’ mobility. The purpose of this study was to investigate how numerical optimization could allow decreasing the energy loss (swiveling and rolling resistance) by numerically adjusting MWC settings, including seat height and ante...

Pressure Ulcer (PU) prevention remains a main public health issue. The physio-pathology of this injury is not fully understood, and a satisfactory therapy is currently not available. Recently, several works suggested that mechanical strains are responsible of deformation-induced damage involved in the initiation of Deep Tissue Injury (DTI). A bette...

The occurrence and management of Pressure Ulcers remain a major issue for patients with reduced mobility and neurosensory loss despite significant improvement in the prevention methods. These injuries are caused by biological cascades leading from a given mechanical loading state in tissues to irreversible tissue damage. Estimating the internal mec...