MAGNETIC-RESONANCE-IMAGING IN THE DIAGNOSIS OF ACUTE INJURED DISTAL TIBIOFIBULAR SYNDESMOSIS

RATIONALE AND OBJECTIVES. This study assessed the diagnostic potential of magnetic resonance imaging for the evaluation of the tibiofibular syndesmosis. METHODS. A total of 38 patients with an acute ankle traum a and clinical suspicion of a syndesmotic tear were prospectively stud ied with conventional plain film radiography and magnetic resonance im aging, Magnetic resonance imaging studies included plain T1-weighted ( T1-w) and T2-weighted (T2-w) sequences and contrast-enhanced T1-w sequ ences 0 to 3 days after trauma. All images were read by two independen t radiologists before surgical intervention, Sensitivity and specifici ty were determined for the two observers and the concordance of the tw o observers were calculated using the interobserver analysis (Kappa-Te st), Intraoperative inspection (n = 21) revealed rupture of the anteri or tibiofibular ligament (ATIF) in 15 patients, intact ATIF in 6 patie nts, and intact posterior tibiofibular ligament (PTIF) in 21 cases, Cl inical and follow-up examinations revealed an intact syndesmotic compl ex in another 17 patients. RESULTS. Primary diagnostic criteria for di agnosing a ligamentous tear included tibiofibular diastasis in convent ional plain films; nonvisualization of the ATIF; an abnormal course, a wavy, irregular contour of the ligament; increased signal intensity o f the ligament in T2-w sequences, in plain T1-w sequence, and marked e nhancement in T1-w after contrast, Important secondary signs were defi ned as joint fluid in the tibiofibular space and prolapse of interspac e fat, Highest diagnostic accuracy was achieved if three or more diagn ostic criteria could be visualized, Both readers performed best with t he enhanced T1-weighted and the T2-weighted images in transverse orien tation, The interobserver analysis resulted in high concordance: Kappa = 0.9 (confidence interval: 0.76 to 1.00) for all patients, and in Ka ppa = 0.76 (confidence interval: 0.45 to 1.0) for surgically treated p atients. CONCLUSIONS. Magnetic resonance imaging of the syndesmotic co mplex is a highly sensitive and specific tool for the pretherapeutic e valuation of syndesmotic injury.