[CT scan evaluation of the syndesmotic diastasis in AO/OTA B and C ankle fractures]

There are anatomical variants of the tibiofibular syndesmosis that lead to changes in the radiographic criteria applied to its injury.

To determine the syndesmotic diastasis using CAT scan in B and C (AO/OTA) ankle fractures and relate the anatomical variants of the tibial incisure with the separation from the fibula.

Comparative, cross-sectional and prolective screening that included all patients with B and C (AO/OTA) ankle fractures who completed their X-ray and CAT scan assessment. The radiographic parameters included the tibiofibular clearance, tibiofibular overlapping and the internal clearance. The length, depth and shape of the tibial incisure were measured with CAT scan. The statistical method used was the chi2.

The total number of patients was 17:8 females (47%) and 9 males (53%), with a mean age of 41 years. Fourteen (82%) had a syndesmotic fracture and 3 had suprasyndesmotic fractures. The CAT scan found 10 concave incisures, 4 irregular and 3 flat ones. The mean depth of the incisure was 2.82 +/- 0.89 mm, and the mean width was 22.18 +/- 3.04. No syndesmotic diastasis was detected radiographically in 6 cases (35.2%); the CAT scan only detected 3 of them (17.7%). The diagnosis of syndesmotic diastasis was made with plain X-rays in 11 cases (64.8%) and with CAT scan in 14 (82.3%) (p = 0.043).

The X-rays are questionable to define the syndesmotic diastasis, so the CAT scan should be considered in cases of a doubtful diagnosis.