Reproducibility and Reliability of Dynamic Ultrasound for Evaluating Tibiofibular Translation in the Sagittal Plane

CATEGORY: Ankle INTRODUCTION/PURPOSE: Syndesmotic instability, when subtle, is challenging to diagnose and requires visualization of the syndesmosis during an applied stress. Ultrasound is a dynamic, non-invasive diagnostic tool that can do so at the point of care, but its reliability and reproducibility remain unclear. The aim of this study is to evaluate reliability and reproducibility of the dynamic use of ultrasonography, a safe and non-invasive imaging technique, for evaluating tibiofibular translation in the sagittal plane. METHODS: Patients with no history of injury to either ankle were included in this study. The distal tibiofibular joint was examined using an ultrasound probe placed anteriorly with the patient in supine position, and posteriorly with the patient in prone position. Sagittal fibular translation was simulated by applying an increasing manual force to the fibula in the sagittal plane: 1) in supine position, anterior to posterior (SAP), 2) in prone position, posterior to anterior (PPA), and 3) in prone position, anterior to posterior (PAP) (Figure 1). Two examiners performed the dynamic examination independently to investigate reproducibility of the test. To test for reliability, the relative position of the fibula and tibia were subsequently measured by three observers; with no force application and at maximum force application, defined as the end point at which increased force did not result in additional fibular translation. Interrater reliability was tested using intraclass correlation coefficients (ICC). RESULTS: In total 34 ankles among 17 patients were included, of which 24 ankles were male (71%). Mean subject age was 25.0 ± 5 years. Substantial agreement was found for all measurements. Anterior measurements of the distance between the ultrasound probe and the tibia and fibula demonstrated ICC’s of 0.98 and 0.98, respectively. PPA demonstrated ICC’s of 0.99 and 0.99, and PAP ICC’s of 0.99, and 0.99. To test for reproducibility the mean tibiofibular delta values of SAP, PPA, and PAP in neutral, and after maximum force application were compared between exams. Exam 1 vs exam 2: SAPneutral, coef. -0.001, p-value 0.895. PPAneutral, coef. -0.06, p-value 0.076. PAPneutral, coef. -0.01, p-value 0.957. SAPmaxforce, coef. -0.03, p-value 0.365. PAPmaxforce, coef. <-0.01, p-value 0.910, PPAmaxforce, coef. -0.08, p-value 0.028. CONCLUSION: Use of dynamic ultrasound is a reliable and accurate technique for measuring changes in sagittal translation of the tibiofibular joint. Substantial variation between right and left ankles of an individual subject is rare, underscoring the significant utility of the contralateral ankle as a control in the injury setting. This test affords a non-invasive means of diagnosing syndesmotic instability in the sagittal plane.