Ankle injury mechanisms: Lessons learned from cadaveric studies

Abstract

The biomechanics of ankle injury have been studied extensively, primarily through mechanical testing of human cadavers. Cadaveric testing is an invaluable methodology in biomechanics, because the magnitude and direction of the loading can be measured precisely and correlated with the resulting injury pattern. Clinical and epidemiological studies provide useful descriptions of injury patterns that occur in the real world, but their retrospective nature precludes a definitive analysis of the forces that caused the injury. Understanding the mechanism of ankle injuries is essential for developing countermeasures to prevent injury and for reconstructing injurious events. Knowledge of an injury's mechanism can also suggest potential associated injuries, which is helpful in diagnosis and treatment. The purpose of this review is to summarize the published research on ankle injury mechanisms with an emphasis on biomechanical experiments on human cadavers. Injury patterns are described based on the principal axis of force or torque producing the injury in conjunction with off-axis forces and out-of-plane foot positions. A mechanistic description of ankle injuries is complicated by the fact that the same mechanism can sometimes produce different injuries and the same injury can sometimes be caused by multiple mechanisms. Nonetheless, a framework for relating injury mechanisms and injury patterns is a valuable tool in the understanding, prevention, and treatment of ankle injuries.

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

“…A clinical review indicates that external rotation of the neutral foot will “first rupture the deltoid ligament, with subsequent injury to the ATiFL.”1 Using a computational model, we also showed that the ADL experiences the highest strain under external rotation of the neutral foot with a compliant foot constraint 25. Other mechanisms potentially causing deltoid ligament damage are excessive eversion, dorsiflexion, or a combination of both 20. However, these were not the subject of our study.…”

“…When an axial load is applied to a dorsiflexed foot (neutral in the coronal plane), the tibial plafond tends to hold the talus tightly in the mortise, resulting in large joint forces generated during external rotation of the talus. In fact, excessive axial loading of a dorsiflexed ankle often produces fractures of the distal tibia or the talus 20. In contrast, an angle is formed between the tibial plafond and the talar dome in an everted foot, causing the talus to move laterally during axial loading, perturbing the mortise, resulting in its ease of rotation.…”

“…Many of these, however, were ligament sectioning studies that showed increased lateral motion of the fibula relative to the tibia during external rotation of the foot as syndesmotic structures were sequentially cut 15–19. Other biomechanical studies were largely designed to investigate ankle fractures rather than sprains 20, 21. For example, a study by Haraguchi and Armiger,22 using a relatively rigid experimental restraint for the foot, showed that external rotation of the foot with the ankle in pronation produced damage to the ATiFL with fibular fracture, followed by medial injury that involved the deltoid ligament.…”

Case series analysis of hindfoot injuries sustained by drivers in frontal motor vehicle crashes

“…The posterior malleolar fracture resulted from external rotation coupled with the axial compressive loading from the foot [5]. Further inversion resulted in an avulsion fracture of the lateral malleolus and displacement of the medial tibial plafond superiorly (Table 8).…”

“…A recent study reviewed the biomechanics of ankle injuries from mechanical testing of human cadavers, and summarized the injury mechanisms based on the principle axis of force or torque applied to injured foot segment [5]. The proposed diagram deciphered experimental data for identifying injury mechanisms given an injury pattern and was referred in current study.…”