Radiographic evaluation of the distal tibiofibular syndesmosis injury in ankle fractures

Abstract

Objective To compare the X-ray and CT manifestations of ruptured distal tibiofibular syndesmosis coupled with ankle fracture for better diagnosis of lower tibiofibular syndesmosis injury.Methods A retrospective study was performed of 36 patients who had been treated in our department for ankle fracture complicated with distal tibiofibular syndesmosis injury from January 2009 to December 2011.They were 16 men and 20 women,18 to 67 years of age (average,41.9 years).They all had anterior-posterior X-ray and CT examinations preoperatively.The clear gaps and lower tibiofibular distances 10 mm above the tibial astragaloid joint were measured respectively on X-ray films and CT scans.The differences were compared between positive X-ray clear gaps and CT lower tibiofibular distances.Results The mean X-ray clear gap 10 mm above the tibial astragaloid joint was 7.95 ± 0.49 mm while the mean CT lower tibiofibular distance 10 mm above the tibial astragaloid joint was 8.48 ± 0.41 mm.The difference was significant (t =-3.376,P =0.002).The ankle mortise was less than 6 mm in 6 X-ray films,giving a rate of missed diagnosis of 16.7％ while the lower tibiofibular distance was hess than 6 mm in 2 CT scans,giving a rate of missed diagnosis of 5.67％.The difference was significant (x2 =2.250,P =0.034).Conclusions Both standard X-ray imaging and CT scan can detect ankle fracture complicated with separation of distal tibiofibular syndesmosis,but CT may lead to a reduced rate of missed diagnosis compared with X-ray,displaying the situation of distal tibiofibular syndesmosis injury more precisely and clearly. Key words: Ankle; Fracture; Joint instability; X-Ray, diagnostic; Computerized tomography