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

Background: 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. Methods: 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. Results: 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. Conclusion: Measurements evaluating the distance between tibia and fibula in the axial plane 10 mm 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.