Reliability of distal tibio-fibular syndesmotic instability measurements using weightbearing and non-weightbearing cone-beam CT

•Syndesmotic measurements on weight bearing CT are feasible and reproducible.•High level of agreement was observed between 3 independent readers.•These measurements should be compared to normal side to determine syndesmosis integrity. To investigate the reliability and reproducibility of syndesmosis measurements on weightbearing (WB) cone-beam computed tomography (CBCT) images and compare them with measurements obtained using non-weightbearing (NWB) images. In this IRB-approved, retrospective study of 5 men and 9 women with prior ankle injuries, simultaneous WB and NWB CBCT scans were taken. A set of 21 syndesmosis measurements using WB and NWB images were performed by 3 independent observers. Pearson/Spearman correlation and intra-class correlation (ICC) were used to assess intra- and inter-observer reliability, respectively. We observed substantial to perfect intra-observer reliability (ICC=0.72–0.99) in 20 measurements. Moderate to perfect agreement (ICC=0.45–0.97) between observers was noted in 19 measurements. Measurements evaluating the distance between tibia and fibula in the axial plane 10mm above the plafond had high intra- and inter-observer reliability. Mean posterior tibio-fibular distance, diastasis, and angular measurement were significantly different between WB and NWB images.