Eversion during external rotation of the human cadaver foot produces high ankle sprains

Abstract

While high ankle sprains are often clinically ascribed to excessive external foot rotation, no experimental study documents isolated anterior tibiofibular ligament (ATiFL) injury under this loading. We hypothesized that external rotation of a highly everted foot would generate ATiFL injury, in contrast to deltoid ligament injury from external rotation of a neutral foot. Twelve (six pairs) male cadaveric lower extremity limbs underwent external foot rotation until gross failure. All limbs were positioned in 208 of dorsiflexion and restrained with elastic athletic tape. Right limbs were in neutral while left limbs were everted 208. Talus motion relative to the tibia was measured using motion capture. Rotation at failure for everted limbs (46.8 AE 6.18) was significantly greater than for neutral limbs (37.7 AE 5.48). Everted limbs showed ATiFL injury only, while neutral limbs mostly demonstrated deltoid ligament failure. This is the first biomechanical study to produce isolated ATiFL injury under external foot rotation. Eversion of the axially loaded foot predisposes the ATiFL to injury, forming a basis for high ankle sprain. The study helps clarify a mechanism of high ankle sprain and may heighten clinical awareness of isolated ATiFL injury in cases of foot eversion prior to external rotation. It may also provide guidance to investigate the effect of prophylactic measures for this injury. ß

Representing Sub-failure Quasi-static Ligament Mechanics and Bone Kinematics in a Human Ankle Finite Element Model

“…Healthy articular cartilage surfaces are smooth, and their interfaces have some of the lowest known coefficients of friction (on the order of 0.01) (Fung, 1993). Therefore it is expected that in situ bone kinematic and ligament responses under quasi-static loads should be smooth, and this has been demonstrated in PMHS tests Johnson & Markolf, 1983;Siegler et al, 1988;Wei et al, 2012). In this study, the refined model responses were substantially smoother, and therefore more physically realistic, than the baseline model responses.…”

“…Stiehl et al (1992) used a more compliant fiberglass cast tape restraint and documented ATiF injury in combination with fibular fracture. Wei et al (2012) reported that dorsiflexion and eversion followed by axial loading and external rotation of the foot generated isolated ATiF injury in all six cadaver ankles tested. This led to the hypothesis that "eversion… predisposes the ATiF to injury, forming a basis for syndesmotic ankle sprains."…”

“…External rotation of the foot relative to the tibia is considered the primary injury mechanism of many syndesmotic ankle sprains (Nussbaum et al 2001). Some studies have suggested that eversion and dorsiflexion also play a role (Nussbaum et al, 2001;Wei et al, 2012). Syndesmotic ankle sprains have also been documented in studies investigating fibular fractures (Haraguchi & Armiger, 2009;Stiehl, Skrade, & Johnson, 1992).…”

“…Syndesmotic ankle sprains, also called high ankle sprains, are ligament injuries to the distal tibiofibular syndesmosis that are more severe and require greater recovery time than lateral ankle sprains (Boytim, Fischer, and Neumann 1991;Guise 1975). In the clinical literature, external rotation ( Figure 1) of the foot relative to the tibia is considered the primary injury mechanism of many syndesmotic ankle sprains (Nussbaum et al 2001;Boytim, Fischer, and Neumann 1991;Waterman et al 2010), however some studies have suggested that eversion and dorsiflexion also play a role (Boytim, Fischer, and Neumann 1991;Wei et al 2012;Sarrafian 1983;Norkus & Floyd 2001;Wolfe et al 2001;Waterman et al 2011). The precise injury mechanism of syndesmotic ankle sprains remains unclear due to limited knowledge of the relationships between gross foot and ankle kinematics and the resultant ligament mechanics.…”

“…Preliminary structural-level validation was done using the response data from PMHS tests by Mait et al (2015) (Figure 21) since they employed the same boundary conditions as the model. Other experimental studies applying external rotation to the foot constrained calcaneus translation as well as the fibula motion Johnson & Markolf, 1983;Wei et al, 2012), which was found to artificially constrain the talus in preliminary simulation analysis.…”