Tibiofibular syndesmosis in acute ankle fractures: additional value of an oblique MR image plane

Objective To evaluate the additional value of a 45° oblique MRI scan plane for assessing the anterior and posterior distal tibiofibular syndesmotic ligaments in patients with an acute ankle fracture. Materials and methods Prospectively, data were collected for 44 consecutive patients with an acute ankle fracture who underwent a radiograph (AP, lateral, and mortise view) as well as an MRI in both the standard three orthogonal planes and in an additional 45° oblique plane. The fractures on the radiographs were classified according to Lauge-Hansen (LH). The anterior (ATIFL) and posterior (PTIFL) distal tibiofibular ligaments, as well as the presence of a bony avulsion in both the axial and oblique planes was evaluated on MRI. MRI findings regarding syndesmotic injury in the axial and oblique planes were compared to syndesmotic injury predicted by LH. Kappa and the agreement score were calculated to determine the interobserver agreement. The Wilcoxon signed rank test and McNemar’s test were used to compare the two scan planes. Results The interobserver agreement (κ) and agreement score [AS (%)] regarding injury of the ATIFL and PTIFL and the presence of a fibular or tibial avulsion fracture were good to excellent in both the axial and oblique image planes (κ 0.61–0.92, AS 84–95%). For both ligaments the oblique image plane indicated significantly less injury than the axial plane ( p