A biomechanical evaluation of clinical stress tests for syndesmotic ankle instability

Displacement transducers were placed across the anterior and posterior tibiofibular ligaments of 17 fresh cadaver (78.4±6.7 years old at death) lower extremities. Displacements induced by various clinical tests (squeeze, fibula translation, Cotton, external rotation, and anterior drawer) were measured with the ankle ligaments intact and after sequential sectioning of the anterior tibiofibular ligament, anterior deltoid ligament, and posterior tibiofibular ligament. None of the syndesmotic stress tests could distinguish which ligaments were sectioned. Furthermore, the small displacements measured during the stress tests (with the exception of the external rotation test) suggest it is unlikely that the displacement induced in injured syndesmoses can be clinically differentiated from normal syndesmoses. Therefore, pain, rather than increased displacement, should be considered the outcome measure of these tests.