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Syndesmotic injuries of the ankle commonly occur by an external rotation force applied to the ankle joint. Ten fresh-frozen lower extremities from cadavers were used. A specially designed apparatus was used to stabilize the specimen and rotate the ankle joint from internally rotated 25° to externally rotated 35° at a rate of 6°/s for 10 cycles. Two stages were tested (stage I, specimens intact; and stage II, simulated pronation external rotation type injury with fixation). Group 1 was fixed with a novel suture construct across the syndesmotic joint, and group 2 was fixed with a single metallic screw. The torque, rotational angle, and 3-dimensional syndesmotic diastasis readings were recorded. Three-dimensional tibiofibular diastasis was identified. The fibula of the intact specimens displaced an average of 8.6 ± 1.7, 2.4 ± 1.0, and 1.4 ± 1.0 mm in the anterior, lateral, and superior direction, respectively, when the foot was externally rotated 35°. The sectioning of the syndesmostic ligaments and deltoid ligament resulted in a significant decrease in syndesmotic diastasis and foot torsional force (p < .05). The ligament-sectioned specimen lost 57% (externally rotated) and 17% (internally rotated) torsional strength compared with the intact specimen. Groups 1 and 2 provided similar biomechanical stability in this cadaveric model of a syndesmosis deficiency., (Copyright © 2014 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.)