Comparative Computed Tomography with Stress Manoeuvres for Diagnosing Distal Isolated Tibiofibular Syndesmotic Injury in Acute Ankle Sprain: a Protocol for an Accuracy-Test Prospective Study.

ABSTRACT Introduction Although there are several imaging options for diagnosing syndesmotic injury, a fundamental question that guides treatment remains unanswered. Syndesmotic instability is still challenging to correctly diagnose, and syndesmotic disruption and true syndesmotic instability should be differentiated. Currently, imaging tests quickly diagnose the severe syndesmotic instability but have difficulty in diagnosing mild and moderate cases. This study aims to investigate which strategy among an existing computed tomography (CT) index test and two new add-on CT index tests with stress manoeuvres can more accurately diagnose syndesmotic instability. The secondary objective is to investigate the participants disability outcomes by applying the Foot and Ankle Ability Measure questionnaire. Methods and analyses This diagnostic accuracy-test study will consecutively select individuals older than 18 years with a clinical diagnosis of suspected acute syndesmotic injury. Three strategies of the CT index test (one in the neutral position and two with stress) will examine the accuracy using magnetic resonance imaging as the reference standard. The external rotation and dorsiflexion of the ankle will guide the stress manoeuvres. Comparison measurements between the injured syndesmosis and the uninjured contralateral side of the same individual will investigate syndesmotic instability, evaluating the rotational and translational relationship between the fibula and tibia. Sensitivity, specificity, area under the ROC curve and likelihoods will compare the diagnostic accuracies of the strategies. Ethics and dissemination The Internal Review Board and the Research Ethics Committee approved this study (registered number 62100016.5.0000.0071). All the participants will receive a spoken description of the aim of the study, and the choice to participate will be free and voluntary. Participants enrolment will occur after signing the written informed consent, including the terms of confidentiality. The results will be presented at national and international conferences and published in peer-reviewed journals and social media. Trial registration number ClinicalTrials.gov (identifier NCT04095598), pre-results. Strengths and limitations of this study This study is the first to examine the accuracy and feasibility of CT with stress manoeuvres for diagnosing syndesmotic instability. The disability outcomes will be used to evaluate syndesmotic instability diagnosed by CT with stress manoeuvres as a prognostic factor. The limitations of this study include the use of MRI as the reference standard test, which, although not perfect, is estimated to have high accuracy compared to the gold-standard arthroscopy.1 An inherent degree of imprecision related to the severity of the ankle sprain and pain exacerbation may occur when the participants themselves control stress manoeuvres; therefore, some variability is unavoidable. Researchers will monitor and investigate the influence of this source of variability on the results.