How To Diagnose Lateral Ankle Injuries

Author(s): 
By Remy Ardizzone, DPM, and Ronald L. Valmassy, DPM

How To Perform And Assess Talar Tilt And Anterior Drawer Tests

   Specific diagnostic tests are required to definitely diagnose instability. Most practitioners perform manual stress X-rays of the ankle. Like most manual tests, accuracy and reproducibility depend on the skill of the practitioner. One can reduce this variability by using a stress device machine, which exerts a constant pressure of 15 kPa in an attempt to displace the talus within the ankle mortise. However, access to such equipment is limited. In either case, the specific diagnostic tests consist of talar inversion stress (talar tilt) and anterior displacement stress (anterior drawer). In most cases, one should apply both tests to the symptomatic as well as the asymptomatic ankle.    Originally described by Farber in 1932, the talar tilt test refers to the angle formed during forceful inversion of the hindfoot between the talar dome and tibial plafond. One may perform this test by cupping the patient’s calcaneus in one’s hand, keeping the thumb clear of the ankle joint, and stabilizing the tibia with the other hand. Then the clinician would invert the calcaneus and talus as far as possible given the patient’s tolerance. The practitioner holds this position while an AP X-ray is taken. If the patient resists movement in any way, then it may be necessary to administer a local anesthetic block to the ankle. Typically, this is not necessary with manual exams but is often required when using a stress device machine. Exact measurements vary but generally the test is considered positive when the angle of talar tilt measures greater than 18 degrees or differs from the contralateral side by more than 5 degrees.7,13    The anterior drawer test consists of manipulating the affected ankle while taking a lateral X-ray view. To perform this test, it is important for the patient to lie partially on the affected side in such a manner as to obtain as true a lateral projection of the ankle as possible. The fibula should be slightly posterior to the line of the X-ray beam, mimicking its anatomic position. Placing the ankle in 10 degrees of plantarflexion improves the sensitivity of the test.14 One should perform an anterior displacement test on the talus by cupping the calcaneus and pulling forward and slightly downward with one hand while stabilizing the tibia with the other hand. There are various methods of measuring this test but typically the test is considered positive when there is a 10 mm excursion of the talus from under the tibia or 3 mm more than the contralateral side.15 Recent studies suggest that measuring the posterior excursion of the tibia from the posterior aspect of the talus may produce more reliable and reproducible measurements.16    These tests also provide insight into which ligaments may be injured. An anterior drawer test indicates injury to the anterior talofibular ligament but does not necessarily exclude injury to the calcaneofibular ligament. The talar tilt test isolates injury to the calcaneofibular ligament.9    While magnetic resonance imaging (MRI) may offer valuable information for an elite or professional athlete in the setting of an acute ankle sprain, it has little to offer when it comes to establishing a diagnosis of chronic instability. This requires dynamic testing such as the anterior drawer and talar tilt stress X-rays.17,18

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