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TECHNICAL PAPERS: Joint/Whole Body

Finite Element Modeling of the First Ray of the Foot: A Tool for the Design of Interventions

[+] Author and Article Information
Sachin P. Budhabhatti

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio 44195; Department of Chemical and Biomedical Engineering, Cleveland State University, Cleveland, Ohio

Ahmet Erdemir

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio 44195

Marc Petre

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio 44195; Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio

James Sferra, Brian Donley

Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio 44195; The Orthopaedics Research Center, Cleveland Clinic, Cleveland, Ohio 44195

Peter R. Cavanagh1

Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio 44195; Department of Orthopaedic Surgery, Cleveland Clinic, Cleveland, Ohio 44195; The Orthopaedics Research Center, Cleveland Clinic, Cleveland, Ohio 44195cavanap@ccf.org

1

Corresponding author.

J Biomech Eng 129(5), 750-756 (Feb 27, 2007) (7 pages) doi:10.1115/1.2768108 History: Received October 17, 2005; Revised February 27, 2007

Disorders of the first ray of the foot (defined as the hard and soft tissues of the first metatarsal, the sesamoids, and the phalanges of the great toe) are common, and therapeutic interventions to address these problems range from alterations in footwear to orthopedic surgery. Experimental verification of these procedures is often lacking, and thus, a computational modeling approach could provide a means to explore different interventional strategies. A three-dimensional finite element model of the first ray was developed for this purpose. A hexahedral mesh was constructed from magnetic resonance images of the right foot of a male subject. The soft tissue was assumed to be incompressible and hyperelastic, and the bones were modeled as rigid. Contact with friction between the foot and the floor or footwear was defined, and forces were applied to the base of the first metatarsal. Vertical force was extracted from experimental data, and a posterior force of 0.18 times the vertical force was assumed to represent loading at peak forefoot force in the late-stance phase of walking. The orientation of the model and joint configuration at that instant were obtained by minimizing the difference between model predicted and experimentally measured barefoot plantar pressures. The model were then oriented in a series of postures representative of push-off, and forces and joint moments were decreased to zero simultaneously. The pressure distribution underneath the first ray was obtained for each posture to illustrate changes under three case studies representing hallux limitus, surgical arthrodesis of the first ray, and a footwear intervention. Hallux limitus simulations showed that restriction of metatarsophalangeal joint dorsiflexion was directly related to increase and early occurrence of hallux pressures with severe immobility increasing the hallux pressures by as much as 223%. Modeling arthrodesis illustrated elevated hallux pressures when compared to barefoot and was dependent on fixation angles. One degree change in dorsiflexion and valgus fixation angles introduced approximate changes in peak hallux pressure by 95 and 22 kPa, respectively. Footwear simulations using flat insoles showed that using the given set of materials, reductions of at least 18% and 43% under metatarsal head and hallux, respectively, were possible.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Initial position and loading of the foot for barefoot simulations. x, y, and z axes point medial, downward, and posterior, respectively. Connectors were placed at the center of rotation of each joint (MTPJ1, IPJ1). Contact with friction was defined between foot and the floor. Loads calculated from the experiments were applied at the base of MT.

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Figure 2

Peak pressures along the longitudinal axis of the first ray at initiation of late stance. Experimental measurements from a representative trial are shown in addition to model predicted plantar pressures using the coarse mesh following optimal bone alignment. Arrows represent the location of the MTH and hallux.

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Figure 3

Validation of the model. (a) Barefoot plantar pressures under MTH and hallux obtained experimentally and from the model (coarse and fine). (b) Timing of hallux peak pressure from experiments and model (coarse and fine) during push-off phase of walking.

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Figure 4

Simulation results for hallux rigidus. (a) Peak pressure under MTH1 and hallux versus locking angle of MTPJ. (b) The timing of peak hallux pressure predicted for various locking angles (indicated by labeled arrows). The horizontal line shows percentage of the late-stance phase, starting at peak forefoot force.

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Figure 5

Simulation results for footwear interventions. (a) Reduction in plantar pressure under MTH and hallux for five different insole materials. (b) Late-stance simulation using flat insole made out of Poron.

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