Determination of In Situ Ankle Ligament Strains in Cases of High and Medial Ankle Sprains

Ankle sprain is a common occurrence in sports, accounting for 10–30% of injuries [1]. While approximately 85% of ankle sprains are lateral ankle injuries, syndesmotic (high) and medial injuries typically result in more time off the field. In order to help limit or mitigate ankle injuries, it is important to understand the mechanisms of injury. While numerous biomechanical studies have been conducted to investigate ankle injuries, most of them are designed to study ankle fractures rather than sprains. Ankle sprains have been graded in the clinical literature and associated with the degree of damage to a ligament resulting from excessive strains [2]. Recently, there have been studies of lateral ankle sprain in laboratory settings [3,4] and based on investigation of game films [5], providing considerable insight into the mechanism of lateral ankle sprain. On the other hand, few biomechanical studies have been conducted on high and medial ankle sprains. A more recent study from our laboratory used human cadaver limbs to investigate such injuries [6]. The study showed that the type of ankle injury, whether medial or high, under excessive levels of external foot rotation depends on the extent of foot eversion [6]. Everted limbs showed isolated anterior tibiofibular ligament injuries (high ankle sprain) only, while neutral limbs mostly demonstrated deltoid ligament failures (medial ankle sprain). Additionally, the study documented grade II (partial tears) and grade III (ruptures) ligament injuries. While a computational ankle model has also been developed and validated to help understand the mechanisms of injury [7], it is a generic model. The objective of the current study was to develop computational, subject-specific models from those cadaver limbs and determine the levels of ligament strain generated in the medial and high ankle injury cases, as well as correlate the grades of injury with ligament strains from the computational model.