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RESEARCH PAPERS

Computational Modeling to Predict Mechanical Function of Joints: Application to the Lower Leg With Simulation of Two Cadaver Studies

[+] Author and Article Information
Peter C. Liacouras

Orthopaedic Research Laboratory, Departments of Biomedical Engineering & Orthopaedic Surgery, Virginia Commonwealth University, Richmond, VA 23298-0694

Jennifer S. Wayne1

Orthopaedic Research Laboratory, Departments of Biomedical Engineering & Orthopaedic Surgery, Virginia Commonwealth University, Richmond, VA 23298-0694jswayne@vcu.edu

1

Corresponding Author.

J Biomech Eng 129(6), 811-817 (May 03, 2007) (7 pages) doi:10.1115/1.2800763 History: Received December 02, 2005; Revised May 03, 2007

Computational models of musculoskeletal joints and limbs can provide useful information about joint mechanics. Validated models can be used as predictive devices for understanding joint function and serve as clinical tools for predicting the outcome of surgical procedures. A new computational modeling approach was developed for simulating joint kinematics that are dictated by bone/joint anatomy, ligamentous constraints, and applied loading. Three-dimensional computational models of the lower leg were created to illustrate the application of this new approach. Model development began with generating three-dimensional surfaces of each bone from CT images and then importing into the three-dimensional solid modeling software SOLIDWORKS and motion simulation package COSMOSMOTION . Through SOLIDWORKS and COSMOSMOTION , each bone surface file was filled to create a solid object and positioned necessary components added, and simulations executed. Three-dimensional contacts were added to inhibit intersection of the bones during motion. Ligaments were represented as linear springs. Model predictions were then validated by comparison to two different cadaver studies, syndesmotic injury and repair and ankle inversion following ligament transection. The syndesmotic injury model was able to predict tibial rotation, fibular rotation, and anterior/posterior displacement. In the inversion simulation, calcaneofibular ligament extension and angles of inversion compared well. Some experimental data proved harder to simulate accurately, due to certain software limitations and lack of complete experimental data. Other parameters that could not be easily obtained experimentally can be predicted and analyzed by the computational simulations. In the syndesmotic injury study, the force generated in the tibionavicular and calcaneofibular ligaments reduced with the insertion of the staple, indicating how this repair technique changes joint function. After transection of the calcaneofibular ligament in the inversion stability study, a major increase in force was seen in several of the ligaments on the lateral aspect of the foot and ankle, indicating the recruitment of other structures to permit function after injury. Overall, the computational models were able to predict joint kinematics of the lower leg with particular focus on the ankle complex. This same approach can be taken to create models of other limb segments such as the elbow and wrist. Additional parameters can be calculated in the models that are not easily obtained experimentally such as ligament forces, force transmission across joints, and three-dimensional movement of all bones. Muscle activation can be incorporated in the model through the action of applied forces within the software for future studies.

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Copyright © 2007 by American Society of Mechanical Engineers
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Figures

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Figure 1

Syndesmotic foot model: Anatomical representation of all the bones of the leg and foot whose three-dimensional structure was reconstructed. Springs represent the ligaments and interosseous membrane (all ligaments/springs not pictured for clarity purposes). 15lbf(67N) of compression load and 24in.lb(2.7Nm) of torsional force were both applied at the cylindrical joint. The tibia, fibula, and talus were free to move while the remaining bones were fixed in space. The boundary control structures to simulate axial compression/rotation of the tibia and support platform for the foot are shown on the proximal tibia and distal foot.

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Figure 2

Inversion foot model: Anatomical representation of all the bones of the leg and foot whose three-dimensional structure was reconstructed. Proximal portions of the tibia and fibula are not pictured, but present in the model. The tibia was fixed and all other bones were allowed to move. The navicular and three cuneiform bones were fixed together and moved as one object (A). The application of the 10lb(45N) force (arrow and circle) in the model was applied to the plantar surface and midway between the distal attachment points of the calcaneofibular (1) and cervical (2) ligaments. All ligaments/springs are not pictured for clarity purposes.

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Figure 3

Internal rotation of the tibia, relative to the global coordinate system, and external rotation of the fibula, relative to the tibia, during application of 24in.lb(2.7Nm) of torque for the configurations evaluated. Error bars represent one standard deviation.

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Figure 4

Translations of the fibula, relative to the tibia, in the anterior/posterior and medial/lateral directions, during application of 24in.lb(2.7Nm) of torque for the configurations evaluated. Error bars represent one standard deviation.

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Figure 5

Elongation of the calcaneofibular ligament in the intact state and inversion angles of the calcaneus before (intact) and after transection of the calcaneofibular ligament in the cadaver study and computational model. Error bars represent one standard deviation.

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