Objective To investigate the utility and medium-term results of a new intra-operative classification system for distal tibiofibular syndesmosis injury in ankle fractures.Methods Between January 2010 to January 2013 our department treated 58 patients diagnosed with displaced,closed Weber B and C ankle fractures.After fixation the fibular fracture,we classify syndesmosis stability as either normal or one of three grades of instability using the fibular hook traction test.This determined further fixation selection and final syndesmosis treatment.Results 41 of 58 cases (71%) demonstrated a tibiofibular syndesmosis injury and 26 (45%) were unstable.Type Ⅰ injury;(<4mm displacement) 26%,type Ⅱ injury (4-7mm displacement) 41%,type Ⅲ injury (>7mm displacement) 3%.Types Ⅱ and Ⅱ are defined as unstable and required stabilisation.Type Ⅲ has multiplanar instability and requires two screws at the syndesmosis.Weber C fractures demonstrate significantly greater degrees of instability than Weber B fractures (X2=15.50,p=0.0014).All patients were followed-up for 12-24 months,no non-union,no screw breakages.Outcome according to the AOFAS scoring system showed good/excellent results in 93 %,no poor outcomes.Conclusion The syndesmosis instability classification system provides a rational and efficient basis for managing syndesmosis instability.Our results from application of the algorithm justify its further evaluation in the treatment of patients with closed displaced Weber B and C ankle fractures.