WHAT RESULTS DO WE GAIN FROM POSTOPERATIVE CT AFTER SYNDESMOTIC SCREW IN ANKLE FRACTURES? NEW RADIOLOGIC AND FUNCTIONAL RESULTS OF A PROSPECTIVE STUDY

Abstract

Objective: 36 patients (male:female= 26:10, mean age 40.6 years) with ankle fractures treated with osteosynthesis including a syndesmotic screw were enrolled in this prospective study. Instability of the distal syndesmosis was proven intraoperatively and then a quadricortical syndesmotic screw was placed.

Patients were mobilized with an AirCast^® ankle brace and cranes for six weeks, then the syndesmotic screw was removed and patients started full weight bearing.

Using the x-rays of the ankle before and after and the CT of both ankles before removal of the syndesmotic screw we evaluated the radiologic results: the syndesmotic interval in the axial cuts, the Espace claire de Chaput (total clear space, TCS) und the medial clear space (MCS). Ventralization of the fibula as a measurement for the position of the fibula in the incisura was defined as the difference between the vertical reference lines of tibia and fibula in the CT. The functional results were evaluated by the scores of Phillips, Olerud/Molander and Weber.

Results: The mean axial interval difference was 0.83 mm (range -2.6 – 4.5), in seven case (19.4%) the interval had been over corrected. There was one case of subluxation of the talus (2.8%). In 3 patients (8.3%) the syndesmotic screw had been corrected in a second operation after the first CT, in 2 cases (5.6%) the syndesmotic screw had been placed after there was suspection of syndesmotic insufficiency in the x-rays which had been verified by CT. Mean ventralization of the fibula was 2.3mm (range 0–6.4). Average TCS was 5.3 mm (range 3.0 – 8.8), mean MCS was 3.3 mm (range 1.0 – 8.2).

The functional scores showed good to very good results in most patients.

Conclusions: Only with CT, the correct placement of the syndesmotic screw can be verified, the syndesmotic interval in the axial cuts can be evaluated and the position of the fibula in the Incisura fibularis can be assesed, therefore CT should be postoperative standard after syndesmotic screw placement. If an ankle fracture has not been treated with a syndesmotic screw, postoperative CT of both ankles should be done in any radiological or clinical suspicion of syndesmotic insufficiency.