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EN
This study investigated the effect of anteromedial (AM) and central anterior cruciate ligament (ACL) reconstructions on the patellofemoral joint (PFJ) contact mechanics during walking and running. Methods: Six knee models were established under a musculoskeletal multibody dynamic framework. The ACL attachment points and muscle volume of the quadriceps femoris and hamstrings were modified to simulate ACL reconstructions and post-operative muscle atrophy. Walking and running simulations were performed to quantify ACL graft force and PFJ contact force. A single stance phase of the motion cycle was divided into eleven time points (periods 0.0–1.0). The computational results were statistically tested at each time point. Results: The results showed that central ACL reconstruction reduced graft force at contralateral toe-off and toe-off phases under walking conditions and the entire cycle under running conditions, with maximal reductions were 10.96 ± 7.42% and 29.00 ± 10.41%, respectively. Compared to AM reconstruction, central reconstruction increased the mean PFJ contact force by up to 2.12 ± 1.17% of body weight during periods 0.4–0.9 of the walking cycle and exhibited a complex pattern during the running cycle. Conclusions: Central ACL reconstruction provided a significantly higher PFJ load compared to AM reconstruction during walking after surgery. No consistent conclusions were reached between the two surgical protocols on PFJ contact force during running. These findings provide clinicians with a better understanding of the PFJ mechanics after ACL reconstruction.
EN
One of the most crucial factors affecting shooting performance is aiming stability, which is affected by the human–gun parameters. The effect of human–gun parameters on performance and biomechanics has not been investigated due to experimental limitations. This paper analyzed the aiming stability and biomechanics under different rifle handling length and supporting length based on experiments and musculoskeletal model. Methods: The aiming performance and balance posture with various rifle handling length and supporting length was obtained by the motion capture system. The artificial neural network was established to map the handling length and supporting length to the body balance posture. The human-gun musculoskeletal model calculated the joint reaction forces and muscle activation with different balance postures. Results: The effect of handling length and supporting length on aiming stability and biomechanics was analyzed. The muscle activation pattern was identified, and it could explain 83.8–98.2% of the variance in aiming stability. Conclusions: The outcomes of this study could find the most suitable human-gun parameters for shooters to improve performance and reduce the risk of musculoskeletal injury.
EN
Investigation of the relationship between changes in hip-joint center and hip loading pre- and post- total hip arthroplasty (THA) is important in evaluating the effect of surgery on motor function. However, few longitudinal studies comparing pre- and post-THA have been reported. The purpose of this study was to determine the effect of changes in hip-joint center pre- and post-THA on the magnitude and direction of hip-joint contact force during the gait cycle, using a patient-specific musculoskeletal model.
EN
Purpose: The aim of the present study was to evaluate the influence of modified morphological parameters of the muscle model and excitation pattern on the results of musculoskeletal system numerical simulation in a cerebral palsy patient. Methods: The modelling of the musculoskeletal system was performed in the AnyBody Modelling System. The standard model (MoCap) was subjected to modifications consisting of changes in morphological parameters and excitation patterns of selected muscles. The research was conducted with the use of data of a 14-year-old cerebral palsy patient. Results: A reduction of morphological parameters (variant MI) caused a decrease in the value of active force generated by the muscle with changed geometry, and as a consequence the changes in active force generated by other muscles. A simulation of the abnormal excitation pattern (MII variant) resulted in the muscle’s additional activity during its lengthening. The simultaneous modification of the muscle morphology and excitation pattern (MIII variant) points to the interdependence of both types of muscle model changes. A significant increase in the value of the reaction force in the hip joint was observed as a consequence of modification of the hip abductor activity. Conclusions: The morphological parameters and the excitation pattern of modelled muscles have a significant influence on the results of numerical simulation of the musculoskeletal system functioning.
EN
Purpose: Children with cerebral palsy (CP) often use a crouch gait pattern that has disturbances in the knee joint kinematics. Although the length and rate of lengthening of the hamstring musculature have been speculated to be the reason that these disturbances are not adequately dissipated, this relationship has not been adequately explored. The purpose of this exploratory investigation was to use simulations of a musculoskeletal model and Floquet analysis to evaluate how the performance of hamstrings musculature during gait may be related to the knee joint instabilities seen in children with CP. Methods: Children with CP and typically developing (TD) children walked on a treadmill as a motion capture system assessed the knee joint kinematics. Floquet analysis was used to quantify the rate that disturbances present at the knee joint were dissipated, and simulations of a musculoskeletal model were used to estimate the in vivo length and velocity of the hamstrings. Pearson correlation coefficients were calculated to determine if there was a relationship between the rate that the disturbances were dissipated and the performance of the hamstring musculature. Results: The children with CP had hamstrings that lengthened more slowly than TD children, and required more strides to dissipate disturbances in the knee joint kinematics. There was negative correlation between the rate that the hamstrings lengthened and the rate that the knee joint disturbances were dissipated. Conclusions: Our results suggest that the ability of children with CP to dissipate the knee joint disturbances may be related to the inability to properly control the hamstring musculature.
EN
An extensive range of studies have been performed to describe kinematics and dynamics of human movements. However, the forces and moments generated by muscles are not measurable. Dynamic simulations are needed to estimate internal loading of the musculo-skeletal system, to establish scientific basis of treatment planning before performing the surgery, and to predict the functional consequences of treatments. In this study, an ankle joint model consisting of 30 bones and 12 muscles was generated by using lower extremity model of OpenSim software. Muscle insertion points were virtually re-defined for simulation of tendon transfer operation of tibialis posterior in treatment of drop foot deformity. Flexion and inversion moments of ankle, and moment arm distances of tibialis posterior before and after operation were investigated comparatively. Tibialis posterior provided the dorsal flexion moment up to 28 N m after transfer, while providing the plantar flexion moment of -14.5 N m before transfer. Moment arm distance became average 33 mm after transfer, while it is average -11 mm before transfer. These increases provided the active dorsal flexion as the treatment of drop foot.
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