MRI versus lateral stress radiography in acute lateral ankle ligament injuries.

Purpose: Our goal was to compare the abilities of MRI and stress radiography to detect the extent of recent lateral ankle ligament inversion injuries.

Method: In this prospective study, 60 athletically active patients (aged 18-45 years) with recent inversion trauma (< or = 7 days) underwent stress radiography and MRI. In 15 patients, the MR findings were reviewed at surgery. Patients were divided into three groups according to severity of ligament injury on MRI (no, one, or two to three ligament tears). Based on bilateral stress radiography, patients were classified into three groups according to the differential degree of talar tilt (< or = 5, 6-14, or > or = 15 degrees) and compared with patients from the MR groups.

Results: Surgery showed MRI to have 74% sensitivity and 100% specificity in the evaluation of complete lateral ankle ligament tears. Agreement between MR and stress radiography groups for the severity of recent lateral ankle ligament tears was poor (kappa = 0.030).

Conclusion: MRI should be performed in young, athletically active patients if surgical intervention is contemplated, especially at 6-14 degrees talar tilt on stress radiography, since stress radiography tends to over- and underestimate the severity of lateral ligament trauma.