How Pathological Gait Kinematics, Increased Femoral Anteversion and Neck Shaft Angle Adversely Affect the Loading Conditions of the Femoral Head During Gait in Children With Cerebral Palsy

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Proximal femoral deformity favors hip extension action and impairs pelvic stability during gait: a simulation study using mri-based musculoskeletal models

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Quantifying individual muscle contribution to three-dimensional reaching tasks

We investigated the individual muscle contribution to arm motion to better understand the complex muscular coordination underlying three-dimensional (3D) reaching tasks of the upper limb (UL). The individual contributions of biceps, triceps, deltoid anterior, medius, posterior and pectoralis major to the control of specific degrees of freedom (DOFs) were examined: Using a scaled musculoskeletal model, the muscle excitations that reproduce the kinematics were calculated using computed muscle control and a forward simulation was generated. During consequent perturbation analyses, the muscle excitation of selected muscles was instantaneously increased and the resulting effect on the specific DOF was studied to quantify the muscle contribution. The calculated muscle contributions were compared to the responses elicited during electrical stimulation experiments. Innovative in our findings is that muscle action during reaching clearly depended on the reaching trajectory in 3D space. For the majority of the muscles, the magnitude of muscle action changed and even reversed when reaching to different heights and widths. Furthermore, muscle effects on non spanned joints were reported. Using a musculoskeletal model and forward simulation techniques, we demonstrate individual position-dependent muscle contributions to 3D joint kinematics of the UL.status: publishe

The effect of including subject-specific geometrical detail using non-rigid deformation on hip loading in CP children with proximal femoral deformity

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Hip contact force in presence of aberrant bone geometry during normal and pathological gait

Children with cerebral palsy (CP) often present aberrant hip geometry, specifically increased femoral anteversion and neck-shaft angle. Furthermore, altered gait patterns are present within this population. We analyzed the effect of aberrant femoral geometry, as present in CP subjects, on hip contact force (HCF) during pathological and normal gait. We ran dynamic simulations of CP-specific and normal gait using two musculoskeletal models (MSMs), one reflecting normal femoral geometry and one reflecting proximal femoral deformities. The combination of aberrant bone geometry and CP-specific gait characteristics reduced HCF compared to normal gait on a CP subject-specific MSM, but drastically changed the orientation of the HCF vector. The HCF was orientated more vertically and anteriorly than compared to HCF orientation during normal gait. Furthermore, subjects with more pronounced bony deformities encountered larger differences in resultant HCF and HCF orientation. When bone deformities were not accounted for in MSMs of pathologic gait, the HCF orientation was more similar to normal children. Thus, our results support a relation between aberrant femoral geometry and joint loading during pathological/normal gait and confirm a compensatory effect of altered gait kinematics on joint loading. © 2014 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res.status: publishe

Aberrant hip geometry affects peak hip joint loading during normal walking

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Sensitivity of predicted muscle forces to the anatomical variability of the musculoskeletal geometry

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Subject-specific geometrical detail rather than cost function formulation affects hip loading calculation

This study assessed the relative importance of introducing an increasing level of medical image-based subject-specific detail in bone and muscle geometry in the musculoskeletal model, on calculated hip contact forces during gait. These forces were compared to introducing minimization of hip contact forces in the optimization criterion. With an increasing level of subject-specific detail, specifically MRI-based geometry and wrapping surfaces representing the hip capsule, hip contact forces decreased and were more comparable to contact forces measured using instrumented prostheses (average difference of 0.69BW at the first peak compared to 1.04BW for the generic model). Inclusion of subject-specific wrapping surfaces in the model had a greater effect than altering the cost function definition.peerreview_statement: The publishing and review policy for this title is described in its Aims & Scope. aims_and_scope_url: http://www.tandfonline.com/action/journalInformation?show=aimsScope&journalCode=gcmb20status: publishe