Human foot three-dimensional finite element of modeling and its biomechanical applications

2007-2008 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Generation of subject-specific, dynamic, multisegment ankle and foot models to improve orthotic design: a feasibility study

ABSTRACT: BACKGROUND: Currently, custom foot and ankle orthosis prescription and design tend to be based on traditional techniques, which can result in devices which vary greatly between clinicians and repeat prescription. The use of computational models of the foot may give further insight in the biomechanical effects of these devices and allow a more standardised approach to be taken to their design, however due to the complexity of the foot the models must be highly detailed and dynamic. METHODS: Functional and anatomical datasets will be collected in a multicentre study from 10 healthy participants and 15 patients requiring orthotic devices. The patient group will include individuals with metarsalgia, flexible flat foot and drop foot. Each participant will undergo a clinical foot function assessment, 3D surface scans of the foot under different loading conditions, and detailed gait analysis including kinematic, kinetic, muscle activity and plantar pressure measurements in both barefoot and shod conditions. Following this each participant will undergo computed tomography (CT) imaging of their foot and ankle under a range of loads and positions while plantar pressures are recorded. A further subgroup of participants will undergo magnetic resonance imaging (MRI) of the foot and ankle. Imaging data will be segmented to derive the size of bones and orientation of the joint axes. Insertion points of muscles and ligaments will be determined from the MRI and CT-scans and soft tissue material properties computed from the loaded CT data in combination with the plantar pressure measurements. Gait analysis data will be used to drive the models and in combination with the 3D surface scans for scaling purposes. Predicted plantar pressures and muscle activation patterns predicted from the models will be compared to determine the validity of the models. DISCUSSION: This protocol will lead to the generation of unique datasets which will be used to develop linked inverse dynamic and forward dynamic biomechanical foot models. These models may be beneficial in predicting the effect of and thus improving the efficacy of orthotic devices for the foot and ankle

Deterioration of stress distribution due to tunnel creation in single-bundle and double-bundle anterior cruciate ligament reconstructions

Bone tunnel enlargement is a common effect associated with knee laxity after anterior cruciate ligament(ACL) reconstruction. Nevertheless, its exact pathomechanism remains controversial. One of the possible reasons could be bone remodeling due to tunnel creation, which changes the stress environment in the joint. The present study aims to characterize the deteriorated stress distribution on the articular surface, which is due to tunnel creation after single-bundle or double-bundle ACL reconstruction. The stress distributions in the knee following ACL reconstruction under the compression, rotation, and valgus torques were calculated using a validated three-dimensional finite element(FE) model. The results indicate that, (a) under compression,von Mises stress is decreased at lateral and posteromedial regions of single/anteromedial (AM) tunnel, whereas it is increased at anterior region of single/AM tunnel in tibial subchondral bone; (b) the concentration of tensile stress is transferred from the articular surface to the location of graft fixation, and tensile stress in subchondral plate is decreased after ACL reconstruction; (c) severe stress concentration occurs between AM and posterolateral tunnels following the double-bundle reconstruction, which may contribute to the tunnel communication after surgery. In summary, the present study affirms that the deterioration of stress distribution occurs near the articular surface, which may cause the collapse of the tunnel wall, and lead to tunnel enlargement.The present study provides an insight into the effect of tunnel creation on articular stress deterioration after single-bundle or double-bundle ACL reconstruction. These findings provide knowledge on the effect of tunnel enlargement after ACL reconstruction in the long term. © 2012 Biomedical Engineering Society.link_to_subscribed_fulltex