A Biomechanical Evaluation of Clinical Stress Tests for Syndesmotic Ankle Instability

Abstract

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.

Syndesmosis injuries

“…The joint is clearly unstable with plain radiographs (greater than 2 mm of medial clear space widening and/or widened syndesmosis) [29]. All clinical tests are positive.…”

Acute and Chronic Injuries to the Syndesmosis

“…This test causes the greatest amount of displacement of the fibula when biomechanically analyzed. 40 A positive test result occurs if pain if reproduced in the syndesmosis. 30,41 The squeeze test involves compressing the proximal fibula to the tibia above the level of the calf, which may separate the bones distally.…”

“…Pain, rather than fibular translation, should be the outcome measure of these tests, because very small amounts of displacement are actually conferred by the physical examination maneuvers. 40 The external rotation stress test can be performed either by sitting while placing the knee in 90 of flexion and applying an external rotatory force on the foot or standing with a single limb stance on the affected side and then rotating the body externally 41,42 (Fig. 1).…”

Syndesmotic Injuries in Athletes

“…Beumer and colleagues al performed a biomechanical evaluation of 5 special tests (squeeze, fibula translation, Cotton, external rotation, and anterior drawer) to determine the degree of distal tibiofibular displacement induced by each test in intact cadaveric ankles and after sectioning of the anterior talofibular ligament, the posterior talofibular ligament, and the deltoid ligament [60]. The average increase in displacement after sectioning of all ligaments was only approximately 1 mm.…”

“…However, the accuracy, prognostic potential, ability to detect severity of injury, or capability to correlate with the degree of instability present have not been well established [55]. A number of exam tests have been developed that include the external rotation test, the Cotton test, the fibular-translation test, the squeeze test, and the crossed-leg test [60]. The squeeze test is performed by compressing the tibia and fibula at midcalf level [61].…”