New Evaluation Method for Lateral Ankle Instability using Ultrasound

Abstract

Category: Ankle; Trauma Introduction/Purpose: Despite the fact that stress fluoroscopy is the most common method of quantifying lateral ankle instability, ultrasound evaluation has grown in popularity as a way to assess ankle stability at the point of care due to its simplicity, accuracy, low cost, and lack of exposure. The aim of this study is to introduce a new method for evaluating lateral ankle instability using ultrasound. Methods: A 37-year-old man with history of lateral ankle ligament injury underwent ultrasound and fluoroscopic evaluation. The anterior drawer distance (ADD) was quantified under anterior drawer stress. During ADD measurement, the patient sat with the knee extended and the heel on the examination table or chair, and the examiner performed the anterior drawer test (Image 1a). The amount of talar movement was measured as an ADD using an ultrasound probe placed on the posteromedial side of the ankle (Image 1b). A lateral clear space (LCS) was also measured under varus stress using ultrasound from the tip of the lateral malleolar to the lateral process of the talus. The aforementioned measurements were repeated under stress fluoroscopy and compared with ultrasound findings. Results: On ultrasound evaluation, the ADD was 7.1 mm and the LCS was 17.1 mm. Furthermore, the stress fluoroscopic evaluation yielded a similar result, with an ADD of 8.7 mm and an LCS of 17.5 mm. Conclusion: Our findings suggest that this new method of evaluation of lateral ankle instability under dynamic ultrasound appears to be a highly accurate and useful alternative for assessing lateral ankle stability at the point of care in a radiation-free, non- invasive, and low-cost manner.