Abstract

Background: Chronic lateral ankle instability describes multiple pathologies affecting the tibiotalar or talocalcaneal articulations of the foot. One quarter of cases are caused by isolated or concomitant subtalar instability. The standard anterior drawer test (ADT) is used in routine clinical practice to assess abnormal movement at the tibiotalar joint. However, a positive test does not discriminate whether excessive translation is at the tibiotalar or subtalar joint. We suggest a modification to the standard ADT which separates the ankle joint translation by manually immobilising the tibiotalar joint in order isolate anterior translation at the subtalar joint. In the presence of a positive ADT, the modified anterior drawer test (MADT) would help discriminate if the pathological translation is at the tibiotalar or the subtalar joint or both.
Methods: Our clinical study was an observational analysis of a cohort of 12 patients who had presented to an outpatient foot clinic in east of England. In addition, a cadaveric study was used to assess subtalar anterior translation.
Results: In 50% of patients who had a clinically positive ADT, the MADT was negative which correlated 100% with Stress Broden radiographic views. Cadaveric analysis was done to show an increase in anterior translation with sequential sectioning of supporting ligaments. We demonstrated an absolute reduction in anterior translation in subtalar instability with the additional posterior force (MADT).
Conclusion: The clinical and cadaveric data supports the use of the MADT as a valuable adjunct in the diagnosis and exclusion of subtalar instability as a cause of symptoms in addition to stress radiography.

Keywords: Subtalar instability; Anterior drawer test; Ankle instability; Subtalar joint