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Research Papers

Specimen-Specific Computational Models of Ankle Sprains Produced in a Laboratory Setting

[+] Author and Article Information
Keith D. Button

Orthopaedic Biomechanics Laboratories,
Michigan State University,
East Lansing, MI 48824

Feng Wei

Rehabilitation Institute of Chicago,
Chicago, IL 60611

Eric G. Meyer

Experimental Biomechanics Laboratory,
Lawrence Technological University,
Southfield, MI 48075

Roger C. Haut

Orthopaedic Biomechanics Laboratories,
Michigan State University,
East Lansing, MI 48824
e-mail: haut@msu.edu

1Corresponding author.

Contributed by the Bioengineering Division of ASME for publication in the Journal of Biomechanical Engineering. Manuscript received May 1, 2012; final manuscript received January 16, 2013; accepted manuscript posted January 29, 2013; published online April 2, 2013. Assoc. Editor: Richard E. Debski.

J Biomech Eng 135(4), 041001 (Apr 02, 2013) (6 pages) Paper No: BIO-12-1169; doi: 10.1115/1.4023521 History: Received May 01, 2012; Revised January 16, 2013; Accepted January 29, 2013

The use of computational modeling to predict injury mechanisms and severity has recently been investigated, but few models report failure level ligament strains. The hypothesis of the study was that models built off neutral ankle experimental studies would generate the highest ligament strain at failure in the anterior deltoid ligament, comprised of the anterior tibiotalar ligament (ATiTL) and tibionavicular ligament (TiNL). For models built off everted ankle experimental studies the highest strain at failure would be developed in the anterior tibiofibular ligament (ATiFL). An additional objective of the study was to show that in these computational models ligament strain would be lower when modeling a partial versus complete ligament rupture experiment. To simulate a prior cadaver study in which six pairs of cadaver ankles underwent external rotation until gross failure, six specimen-specific models were built based on computed tomography (CT) scans from each specimen. The models were initially positioned with 20 deg dorsiflexion and either everted 20 deg or maintained at neutral to simulate the cadaver experiments. Then each model underwent dynamic external rotation up to the maximum angle at failure in the experiments, at which point the peak strains in the ligaments were calculated. Neutral ankle models predicted the average of highest strain in the ATiTL (29.1 ± 5.3%), correlating with the medial ankle sprains in the neutral cadaver experiments. Everted ankle models predicted the average of highest strain in the ATiFL (31.2 ± 4.3%) correlating with the high ankle sprains documented in everted experiments. Strains predicted for ligaments that suffered gross injuries were significantly higher than the strains in ligaments suffering only a partial tear. The correlation between strain and ligament damage demonstrates the potential for modeling to provide important information for the study of injury mechanisms and for aiding in treatment procedure.

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References

Figures

Grahic Jump Location
Fig. 1

Setup for the cadaver experiment by Wei et al., adapted from [13]. The proximal end of the tibia and fibula was potted and placed in an aluminum box. The foot was taped to a plate using athletic tape, placed in a rectangular tray, and everted, with a marker array on the talus and tibia.

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Fig. 2

The cadaver taping pattern (a) and the model taping pattern represented by springs (b). Note: for clarity all ligament springs and the plate springs on the medial side of the ankle were set invisible.

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Fig. 3

Injury mechanisms reported from the cadaver study by Wei et al. [13]. Partial tear of the ATiFL (a); rupture of the ATiFL (b); partial tear of the ATiTL (c); rupture of the ATiTL (d); tibial avulsion of the ATiTL (e); partial tear of the TiNL (f). Note: the location of injury is shown with a hemostat.

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Fig. 4

Ligaments with average model predicted strains greater than 2% for the neutral case in 3 of 4 cases in which ligament injury occurred. The two solid lines represent the average value in this study for the overall rupture and partial tear strain levels (31.8% and 25.5%, please refer to the Results). The figure includes the calcaneofibular ligament (CaFL) and posterior talofibular ligament (PTaFL).

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Fig. 5

Strains in the ATiFL and the two deltoid ligaments (ATiTL and TiNL) for the neutral case for each specimen modeled. The two solid lines represent the average value in this study for the overall rupture and partial tear strain levels (31.8% and 25.5%, please refer to the Results).

Grahic Jump Location
Fig. 6

Ligaments with average model predicted strains greater than 2% for the everted case. The two solid lines represent rupture and partial tear strain levels (31.8% and 25.5%, please refer to the Results section). The figure includes the calcaneofibular ligament (CaFL) and posterior talofibular ligament (PTaFL).

Grahic Jump Location
Fig. 7

Strains in the ATiFL and the two deltoid ligaments (ATiTL and TiNL) for the everted case for each specimen. The two solid lines represent the average value in this study for the overall rupture and partial tear strain levels (31.8% and 25.5%, please refer to the Results section).

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