Committee Chair

Goulet, Ronald U.

Committee Member

Owino, Joseph O.; Wilkerson, Gary B.; Alvarez, Richard G.

Department

Dept. of Engineering

College

College of Engineering and Computer Science

Publisher

University of Tennessee at Chattanooga

Place of Publication

Chattanooga (Tenn.)

Abstract

Several cadaveric and in vivo biomechanical studies have looked at the effects that ligament injuries of the ankle joint complex have on the stability of the ankle joint and susceptibility to chronic degeneration of articular surfaces, but the re have been very few studies that use computer simulation and the finite element method to evaluate how a n ankle ligament injury affects stability, joint pressure, and potential subsequent failure points. Evidence shows that ankle instability is associated with excessive rotation of the talus in transverse plane, which contributes to articular surface degeneration. It has been documented that after disruption of the anterior talofibular ligament that additional load is placed on the posterior tibiotalar ligament, which leads to further rotational instability. Disruption of the interosseous talocalcaneal ligament creates a more complex instability that leads to chronic joint instability of both the talocrural and subtalar joints. A 3D model of the ankle joint was created using CT image data of a cadaver lower limb. A tetrahedral mesh was created and the bone modulus was assume d uniform. Tendons were represented by simple truss elements and surface to surface contact regions were established to facilitate joint motion. The tibia was fixed and internal rotation in the transverse plane was applied to the foot in the neutral position by means of a 5000 N-mm moment. Force displacement data was compared to experimental data collected using an MTS test frame on a cadaver specimen, and previously published data from an arthrometer study. The anterior talofibular ligament (ATFL) was then removed and compared to MTS and arthrometer load and displacement data. Joint pressures were calculated from the finite element model to evaluate potential lesion spots as well as ligament forces in the deep posterior tibiotalar ligament (DPTTL). Results show a correlation in the change in magnitude from intact to ATFL cut states in the FEA model to the in vitro testing methods. The model predicts a medial shift in contact pressures under internal rotation which has been shown to be a potential location for lesions in ankles with lateral instability. The model also predicts that the DPTTL carries a majority of the resistant forces in the ligaments in internal rotation when the ATFL has been compromised.

Degree

M. S.; A thesis submitted to the faculty of the University of Tennessee at Chattanooga in partial fulfillment of the requirements of the degree of Master of Science.

Date

5-2010

Subject

Ankle -- Mechanical properties; Orthopedics

Discipline

Engineering

Document Type

Masters theses

Extent

v, 41 leaves

Language

English

Rights

Under copyright.

License

http://creativecommons.org/licenses/by-nc-nd/3.0/

Included in

Engineering Commons

Share

COinS