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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.

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.