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Background Excessive Knee Flexion Gait Pattern (KFGP) is a common gait deviation in many pathological conditions. The contractures of the muscles that have been identified as being responsible of KFGP are: iliopsoas, hamstring and gastrocnemius. Research question How do isolated contractures of the iliopsoas, hamstrings and gastrocnemius impact knee flexion during gait? Methods Three levels of contracture (mild, moderate and severe) were simulated bilaterally using an exoskeleton on 10 healthy participants for iliopsoas, hamstring and gastrocnemius muscles. A gait analysis session was performed to evaluate the joint kinematics according to the different simulated contractures. Thirty one parameters were chosen to analyze the kinematics of the thorax, pelvis, hip, knee and ankle. A principal component analysis (PCA) was used to determine the kinematic parameters influenced by contractures. Results In addition to a permanent knee flexion observed for the three muscles with contracture: the contracture of the iliopsoas induces a large hip flexion with pronounced anterior pelvis tilt; the contracture of the hamstrings induces an ankle dorsiflexion during the support phase with a posterior pelvis tilt; the contracture of the gastrocnemius induces an absence of first and second rocker of the ankle with a slight flexion of hip and a slight anterior pelvis tilt. Significance These results support the identification of the muscles responsible for a KFGP. A better knowledge of the interactions between contractures and associated joint kinematics of the same and adjacent joints will support the interpretation of gait analyses by more precisely and faster targeting the concerned muscle.

Low back pain (LBP) is the leading cause of disability worldwide since 1990. Its chronic form (lasting longer than 3 months) affects 10 to 15% of cases and represents 70 to 90% of the total cost of low back pain. Most LBP is classified as non-specific because the pain’s source cannot be precisely established in 85%–90% of cases. The need to identify subgroups of nonspecific chronic low back pain (NSCLBP) was highlighted by both clinicians and researchers in order to optimize therapeutic management. In this context, a project of NSCLBP subgroup identification based on a multifactorial approach has been established. Indeed, several factors contribute to the development and the persistence of NSCLBP. Alterations in the activity of the lumbar muscles have been suggested as one of these contributing factors. This doctoral work has focused on these alterations and represent a part of the subgroup identification project.Literature reported various alterations in the lumbar muscles activity of the NSCLBP patients during several tasks. Among these alterations, neuromuscular asymmetry between the left and right side was reported to influence muscle recruitment, rehabilitation and persistence of pain. These elements make neuromuscular asymmetry an important factor in understanding the pathophysiology of NSCLBP. However, few studies have investigated right / left asymmetry of lumbar muscle activity during functional tasks of the daily life. Studying this asymmetry would allow a better understanding of the pathophysiology of NSCLBP.This doctoral work aimed to characterise the neuromuscular asymmetry of NSCLBP patients in comparison with asymptomatic participants. To achieve this objective, several complementary studies were successively conducted.As a whole, this doctoral work highlights a global alteration of the activity of the lumbar muscles in NSCLBP patients during the four motor tasks studied. Most of these alterations aimed to enhance the stability of the spine but lead to potential long-term consequences. Neuromuscular asymmetry is one of these alterations but seems to be present only during maximal trunk forward bending. Considering the clustering project is mainly based on the alterations observed in the NSCLBP population, the integration of the asymmetry of the flexion-relaxation phenomenon may represent an interesting parameter in the process of identification of the subgroups. It would also be useful to extend the analysis to the abdominal and pelvis muscles as well as to evaluate the influence of the psychological parameters for a deeper understanding of these results.; Les lombalgies représentent la principale cause d'invalidité dans le monde depuis 1990. Sa forme chronique (durée supérieure à 3 mois) affecte 10 à 15% des cas et représente 70 à 90% du coût total lié aux lombalgies. De plus, un diagnostic précis ne peut être obtenu que dans 10-15% des cas en raison d'un manque de connaissances de la pathophysiologie catégorisant ces lombalgies comme non-spécifiques. Chercheurs et cliniciens ont mis en avant le besoin d’identifier des sous-groupes au sein de la population lombalgique chronique non-spécifique (NSCLBP) afin d’optimiser la prise en charge thérapeutique. Dans ce contexte, un projet de classification des patients NSCLBP intégrant une approche multifactorielle a été mis en place. En effet, divers facteurs contribuent au développement et à la persistance des NSCLBP. Parmi ces facteurs, on retrouve les altérations de l’activité des muscles lombaires. Ces travaux de thèse se sont intéressés à ces altérations et représentent une partie du projet d’identification des sous-groupes.La littérature met en évidence différentes altérations dans l’activité électromyographique (EMG) des muscles lombaires chez les patients NSCLBP lors de l’exécution de plusieurs tâches fonctionnelles telles que la marche, le soulever de charge, le transfert assis-debout et encore la montée d’escaliers. Parmi ces altérations EMG, l’asymétrie neuromusculaire entre le côté droit et le côté gauche a montré une influence sur l’effet de la réhabilitation, le recrutement musculaire et la persistance de la douleur. Ces éléments font de l’asymétrie neuromusculaire un facteur important pour la compréhension de la pathophysiologie des NSCLBP. Cependant, peu d’études, à ce jour, se sont intéressées à l’asymétrie droite/gauche de l’activité des muscles lombaires. Étudier cette asymétrie pourrait permettre une meilleure compréhension de la pathophysiologie des NSCLBP.L’objectif de cette thèse était donc de caractériser l’asymétrie de l’activité des muscles lombaires lors de différentes tâches motrices et d’évaluer sa pertinence dans le processus d’identification de sous-groupes de patients NSCLBP. Pour répondre à ces objectifs, quatre études complémentaires ont été menées au cours de tâches motrices nécessitant un mouvement synchrone entre droite et gauche.Dans leur ensemble, ces travaux de thèse mettent en évidence une altération globale de l’activité EMG des muscles lombaires au cours des quatre tâches motrices étudiées que sont le test de Sorensen, la flexion antérieure maximale du tronc, le transfert assis-debout et le soulever de charge. Malgré le fait que certaines altérations permettent une augmentation de la stabilité du tronc, elles peuvent toutes avoir des conséquences nocives à long terme. L’asymétrie neuromusculaire est l’une de ces altérations mais elle ne semble présente que lors de la tâche de flexion antérieure maximale du tronc. Considérant que le projet de classification se base principalement sur les altérations observées dans la population NSCLBP, l’intégration de l’asymétrie du phénomène de flexion-relaxation peut représenter un intérêt certain dans le processus d’identification des sous-groupes. Il serait aussi pertinent d’étendre l’analyse aux muscles de l’abdomen et du bassin ainsi que d’évaluer l’influence des paramètres psychologiques pour une compréhension plus complète de ces résultats.

Musculoskeletal models generally solve the muscular redundancy by numerical optimisation. They have been extensively validated using instrumented implants. Conversely, a reduction approach considers only one flexor or extensor muscle group at the time to equilibrate the inter-segmental joint moment. It is not clear if such models can still predict reliable joint contact and musculo-tendon forces during gait. Tibiofemoral contact force and gastrocnemii, quadriceps, and hamstrings musculo-tendon forces were estimated using a reduction approach for five subjects walking with an instrumented prosthesis. The errors in the proximal-distal tibiofemoral contact force fell in the range (0.3-0.9 body weight) reported in the literature for musculoskeletal models using numerical optimisation. The musculo-tendon forces were in agreement with the EMG envelops and appeared comparable to the ones reported in the literature with generic musculoskeletal models. Although evident simplifications and limitations, it seems that the reduction approach can provided quite reliable results. It can be a useful pedagogical tool in biomechanics, e.g. to illustrate the theoretical differences between inter-segmental and contact forces, and can provide a first estimate of the joint loadings in subjects with limited musculoskeletal deformities and neurological disorders.

Background Obtaining precise and repeatable measurements is essential to clinical gait analysis. However, defining the thigh medial-lateral axis segment remains a challenge, with particular implications for the hip rotation profile. Thigh medial-lateral axis misalignment modifies the hip rotation profile and can result in a phenomenon called crosstalk, which increases knee adduction-abduction amplitude artificially. Research question This study proposes an a posteriori geometrical method based solely on segment anatomy that aims to correct the thigh medial-lateral axis definition and crosstalk-related error. Methods The proposed method considers the thigh medial-lateral axis as the normal to the mean sagittal plane of the lower limb defined by hip, knee and ankle joint centres during one gait cycle. Its performance was compared to that of an optimisation method which repositions the axis to reduce knee abduction-adduction variance. An existing dataset was used: 75 patients with a knee prosthesis undergoing gait analysis three months and one-year post-surgery. Three-dimensional hip and knee angles were computed for two gait analysis sessions. Crosstalk was quantified using both the coefficient of determination (r²) between knee flexion-extension and adduction-abduction and the amplitude of knee adduction-abduction. The reproducibility of hip internal-external rotation was also quantified using the inter-trial, inter-session and inter-subject standard deviations and the intraclass coefficient (ICC). Results Crosstalk was significantly reduced from r² = 0.67 to r² = 0.51 by the geometrical method but remained significantly higher than with the optimisation method with a r² Significances Both methods allowed to improve the hip internal-external reproducibility from poor to moderate (original data: ICC = 0.34, geometrical method: ICC = 0.65, optimisation method ICC = 0.73). One advantage of the geometrical method is that, unlike the optimisation method, it does not require much movement, making it suitable for a wider range of patients.

Contracture is a permanent shortening of the muscle-tendon-ligament complex that limits joint mobility. Contracture is involved in many diseases (cerebral palsy, stroke, etc.) and can impair walking and other activities of daily living. The purpose of this study was to quantify the reliability of an exoskeleton designed to emulate lower limb muscle contractures unilaterally and bilaterally during walking. An exoskeleton was built according to the following design criteria: adjustable to different morphologies; respect of the principal lines of muscular actions; placement of reflective markers on anatomical landmarks; and the ability to replicate the contractures of eight muscles of the lower limb unilaterally and bilaterally (psoas, rectus femoris, hamstring, hip adductors, gastrocnemius, soleus, tibialis posterior, and peroneus). Sixteen combinations of contractures were emulated on the unilateral and bilateral muscles of nine healthy participants. Two sessions of gait analysis were performed at weekly intervals to assess the reliability of the emulated contractures. Discrete variables were extracted from the kinematics to analyse the reliability. The exoskeleton did not affect normal walking when contractures were not emulated. Kinematic reliability varied from poor to excellent depending on the targeted muscle. Reliability was good for the bilateral and unilateral gastrocnemius, soleus, and tibialis posterior as well as the bilateral hamstring and unilateral hip adductors. The exoskeleton can be used to replicate contracture on healthy participants. The exoskeleton will allow us to differentiate primary and compensatory effects of muscle contractures on gait kinematics.

Background Contractures of a major joint in the lower limbs may impair human walking in addition to other daily living activities. A contracture is defined as the inability of a joint to perform the full range of motion and excessive resistance during passive mobilization of the joint. Few studies have reported methods describing how to evaluate contractures. Understanding the association among all of these studies seems essential to improve patient management. Therefore, we conducted a systematic review on this topic to elucidate the influence of contractures on gait kinematics. Methods An electronic search in the literature will be conducted. Studies were screened by title and abstract and full texts were evaluated secondarily for definitive inclusion. The quality of the included studies was assessed independently by the two review authors with the Modified Quality Assessment Checklist. The included studies were separated into three categories: pathological contracture versus healthy controls (descriptive), simulated contracture versus healthy controls (experimental), and pre- and post-kinematics after surgical muscle lengthening (surgery). Findings From a total of 4402 references, 112 original articles were selected, and 28 studies were identified in this systematic review. No significant difference between raters was observed on the total score of the Modified Quality Assessment Checklist. Interpretation Contractures influence walking depending on the location (muscle) and the contracture level (muscle–tendon length). After giving a definition of contracture, this review identified some contracture alterations, such as plantarflexion, knee flexion and hip flexion contractures, with a kinematic description and presented possible different compensations.

15th International Symposium on 3-D Analysis of Human Movement, Manchester, ROYAUME-UNI, 03-/07/2018 - 06/07/2018; Stereophotogrammetry has been widely used for measuring gait. Conventional gait analysis systems tend to be based on the Davis marker-set [1]. This marker-set is dependent on the position of a wand on the thigh to define medial-lateral thigh axis. This wand is supposed to lie in the frontal plane of the thigh and can be difficult to position properly. A poor positioning leads to axis misorientation which can cause errors known as crosstalk. Crosstalk corresponds to an unphysiological knee Abduction Adduction (AA) amplitude correlated with knee Flexion-Extension (FE) [2]. This phenomenon also affects hip Internal External Rotation (IER) which is a parameter of high interest in clinical gait analysis (CGA). Several methods have been proposed previously to better define the medial-lateral axis of the thigh and improve the quality of both hip and knee kinematics. However, the corrections were not always satisfying or difficult to implement [2-3].

Introduction Ankle plantarflexion contracture results from a permanent shortening of the muscle-tendon complex. It often leads to gait alterations. The objective of this study was to compare the kinematic adaptations of different degrees of contractures and between isolated bilateral gastrocnemius and soleus emulated contractures using an exoskeleton. Methods Eight combinations of contractures were emulated bilaterally on 10 asymptomatic participants using an exoskeleton that was able to emulate different degrees of contracture of gastrocnemius (biarticular muscle) and soleus (monoarticular muscle), corresponding at 0°, 10°, 20°, and 30° ankle plantarflexion contracture (knee-flexed and knee-extended). Range of motion was limited by ropes attached for soleus on heel and below the knee and for gastrocnemius on heel and above the knee. A gait analysis session was performed to evaluate the effect of these different emulated contractures on the Gait Profile Score, walking speed and gait kinematics. Results Gastrocnemius and soleus contractures influence gait kinematics, with an increase of the Gait Profile Score. Significant differences were found in the kinematics of the ankles, knees and hips. Contractures of soleus cause a more important decrease in the range of motion at the ankle than the same degree of gastrocnemius contractures. Gastrocnemius contractures cause greater knee flexion (during the stance phase) and hip flexion (during all the gait cycle) than the same level of soleus contractures. Conclusion These results can support the interpretation of the Clinical Gait Analysis data by providing a better understanding of the effect of isolate contracture of soleus and gastrocnemius on gait kinematics.

22nd Congress of the European Society of Biomechanics (ESB), LYON, FRANCE, 10-/07/2016 - 13/07/2016; Contracture is a permanent shortening of the muscle - tendon - ligament complex that limits joint mobility. Contracture is involved in many diseases (cerebral palsy (CP), stroke, etc.) and can impair walking. Ankle equinus is one of the most common gait deviations (due to soleus and gastrocnemius muscle contractures) in cerebral palsy compromising the first (heel rocker) and second (ankle rocker) rockers of the foot during walking. Moreover, soleus and gastrocnemius contractures have different effects on gait kinematics and these effects are dependant of the degree of contracture. Thus, a good understanding of gait deviations is important to choose the best therapeutic approach, especially to optimise surgical procedures. This study aimed to evaluate the effect of gastrocnemius and soleus contractures on the first and second rocker during walking.

Epub ahead of print; The aim of this study was to compare the kinetic and kinematic parameters of standing and crouch sprint starts. Parallel starts (PS), false starts (FS), jump starts (JS) and crouch starts (3PS) were compared. Eighteen participants performed each start on a force plate and six infrared cameras captured the three-dimensional coordinates of 36 retro-reflective markers. Performance during a five-metre sprint (T5m) was analysed. Duration of the start phase (Tstart), mean values of horizontal and total ground reaction forces (GRFs) (Fx_mean and Ftot_mean), ratio of force (RF), maximal power (Pmax) and kinetic energy (KE) of each limb were calculated. Significant differences were found for T5m, Tstart, KE, Pmax, Fx_mean, Ftot_mean and RF for the crouch start compared to the other starts (P ≤q 0.05). Significant correlations were found between T5m and Tstart (r = 0.59; P ≤q 0.001), and T5m and Pmax, Fx_mean and RF (-0.73 ≤q r ≤q -0.61; P ≤q 0.001). To conclude, the crouch start resulted in the best performance because Tstart was shorter, producing greater Pmax, Fx_mean with a more forward orientation of the resultant force. Greater KE of the trunk in each start condition demonstrated the role of the trunk in generating forward translation of the centre of mass (CM).

International audience; The aim of this study was to evaluate whether clinical parameters are sufficient using, a multilinear regression model, to reproduce the sagittal plane joint angles (hip, knee, and ankle) in cerebral palsy gait. A total of 154 patients were included. The two legs were considered (308 observations). Thirty-six clinical parameters were used as regressors (range of motion, muscle strength, and spasticity of the lower). From the clinical gait analysis, the joint angles of the sagittal plane were selected. Results showed that clinical parameter does not provide sufficient information to recover joint angles and/or that the multilinear regression model is not an appropriate solution.

Background Lower limb deficits have been widely studied during gait in cerebral palsy, deficits in upper body have received little attention. The purpose of this research was to describe the characteristics of trunk movement of cerebral palsy children in terms of type of deficits (diplegia/hemiplegia) and gross motor function classification system (1, 2 or 3). Methods Data from 92 cerebral palsy children, which corresponds to 141 clinical gait analysis, were retrospectively selected. Kinematic parameters of trunk were extracted from thorax and spine angles in the sagittal, transverse and coronal planes. The range of motion and the mean positions over the gait cycle were analysed. Intra-group differences between the children with diplegia or hemiplegia, gross motor function classification systems 1 to 3 and typically developing participants were analysed with Kruskal–Wallis tests and post hoc tests. Pearson correlation coefficients between the gait profile score normalised walking speed and kinematic parameters of the thorax were assessed. Findings The results revealed: 1) the range of motion of the thorax and spine exhibited more significant differences between groups than the mean positions; 2) greater levels of impairment were associated with higher thorax range of motion, and 3) the children with diplegia and gross motor function classification system 3 exhibited a greater range of motion for all planes with the exception of spine rotation. Interpretation This study confirmed that greater levels of impairment in cerebral palsy are associated with greater thorax range of motion during gait. The thorax plays an important role during gait in cerebral palsy.

International audience; BACKGROUND:Evolution; Gait; Hereditary spastic paraplegia; Longitudinal study; WalkingThe degree of disability in patients with hereditary spastic paraplegia has been reported variable even in members of the same family (same gene mutation). Moreover, it has been established that patients with hereditary spastic paraplegia should be treated differently from cerebral palsy patients due to the progressive nature of this disease. However, the gait evolution of hereditary spastic paraplegia showing onset symptoms at an early age has been described as stable. Therefore, this study aims to evaluate the walking ability and the influence of treatments on gait evolution in a family with hereditary spastic paraplegia.METHODS:Clinical gait analyses were performed in six hereditary spastic paraplegia patients from the same family with a follow-up of 4-15 years.RESULTS:Based on the gait deviation index, results showed a large variation of walking ability in these patients and no statistical difference between the first and last examination. In fact, three patients have improved their gait (from childhood to adolescence) whereas three patients worsened their gait.CONCLUSIONS:Gait alterations in a family with hereditary spastic paraplegia are heterogeneous. Gait evolution in hereditary spastic paraplegia with early symptoms had a tendency to improve gait until adolescence with adapted treatments and to decline in the adulthood.