702 Hindfoot Stability Test - Introduction and Validation of a Diagnostic Test of Subtalar Instability in Deltoid Ligament Injury Associated with Ankle Fractures

Abstract

Abstract Aim Deltoid ligament complex (DLC) injury repair in the presence of an ankle fracture remains a topic of controversy in the current literature. No work in the current literature has commented on hindfoot and subtalar instability in the presence DLC injury associated with ankle fracture fixation. Our aim was to introduce and validate a new method for assessment of hindfoot instability, when fixing an ankle fracture with associated DLC injury. Method DLC injury, specifically superficial DLC, controls not only the ankle but the subtalar joint and medial longitudinal arch. Valgus stressing can unmask subtalar instability. It was noted by referencing the hindfoot position to a line parallel with the lateral aspect of the fibula, the lateral fibula line, subtalar instability was probable. We used six morphologically normal cadaveric specimens to validate the test. Results Six cadaveric specimens were used for validation of the hindfoot stability test. Pre-injury, no specimen illustrated bisection of the calcaneal tuberosity by the lateral fibular line on hindfoot stability test under fluoroscopy. Post-injury, all specimens showed bisection of the calcaneal tuberosity by the lateral fibular line on hindfoot stability test. Conclusions The hindfoot stability test assesses hindfoot stability on valgus stressing of the hindfoot using the calcaneal tuberosity bisection of a line drawn from the lateral border of the fibula as a reference point for instability. This was validated using morphologically normal cadavers.