A framework for parametric modeling of ankle ligaments to determine thein situresponse under gross foot motion

Abstract

Ligament sprains account for a majority of injuries to the foot and ankle complex, but ligament properties have not been understood well due to the difficulties in replicating the complex geometry, in situ stress state, and non-uniformity of the strain. For a full investigation of the injury mechanism, it is essential to build up a foot and ankle model validated at the level of bony kinematics and ligament properties. This study developed a framework to parameterize the ligament response for determining the in situ stress state and heterogeneous force-elongation characteristics using a finite element ankle model. Nine major ankle ligaments and the interosseous membrane were modeled as discrete elements corresponding functionally to the ligamentous microstructure of collagen fibers and having parameterized toe region and stiffness at the fiber level. The range of the design variables in the ligament model was determined from existing experimental data. Sensitivity of the bony kinematics to each variable was investigated by design of experiment. The results highlighted the critical role of the length of the toe region of the ligamentous fibers on the bony kinematics with the cumulative influence of more than 95%, while the fiber stiffness was statistically insignificant with an influence of less than 1% under the given variable range and loading conditions. With the flexibility of variable adjustment and high computational efficiency, the presented ankle model was generic in nature so as to maximize its applicability to capture the individual ligament behaviors in future studies.

Propagation of Syndesmotic Injuries During Forced External Rotation in Flexed Cadaveric Ankles

“…From these objectives, it was hypothesized that ankle flexion will alter the incidence of syndesmotic injuries and the sequence of ankle injuries during forced external rotation. These results are anticipated to have relevance in both clinical and biomechanical research 20 , 21 settings.…”

“…The injury sequence information determined in this study will enlighten clinical classifications of syndesmotic injuries to improve future care, recovery, and prevention methods. A current finite element model 20 , 21 will be validated with this injury sequence to refine injury prediction capabilities within that model, with the ultimate goal of informing future diagnostic capabilities and countermeasure designs for reducing the incidence of syndesmotic ankle sprains in the field.…”

Syndesmotic Ankle Sprains in Large Males

“…Intervals of injury occurrence relative to these tibiofibular kinematic interactions (i.e., tibiofibular diastasis) were also given in this thesis. These intervals (relative to external foot rotation, fibula displacement, and tibiofibular rotation differences) present a direct link between the injury mechanisms of syndesmotic ankle sprains, both externally applied (external foot rotation) and the resultant internal load applied to the ankle syndesmosis joint (tibiofibular diastasis) Ultimately, the kinematic-based injury occurrence intervals, in conjunction with the injury sequence data, will be implemented to improve injury-predictive capabilities of a finite element computational model (Mane, 2016;Mane et al, 2015;Nie et al, 2017bNie et al, , 2017aNie et al, , 2016bNie et al, , 2016a, which should be used as a design tool for any future countermeasure or injury mitigation technique.…”

“…In parallel to the experimental efforts detailed in this thesis, computational modeling improvements were also completed (Mane, 2016;Mane et al, 2015;Nie et al, 2017bNie et al, , 2017aNie et al, , 2016bNie et al, , 2016a to study syndesmotic ankle sprain mechanics. The experimental kinematic and injury data detailed in this thesis was used to validate this finite element model, with the goal of creating a biofidelic model for predicting syndesmotic ankle sprains (Figure 35).…”

“…A biofidelic finite element model (Figure 35), validated to the ankle bone kinematics and ligament failure propagations detailed in this thesis (Figure 26), can be implemented as an ankle surrogate in the future (Mane, 2016;Mane et al, 2015;Nie et al, 2017bNie et al, , 2017aNie et al, , 2016bNie et al, , 2016a, thus reducing the need for cadaveric testing. This validated ankle surrogate has the capability to investigate the effects of taping/braces, parallel load paths, shoe plate compliance, and cleat-turf interactions on syndesmotic injury.…”