A Novel Model for Predicting the Sagittal Length of the Distal Tibia Using CT Imaging and Statistics

The purpose of this study was to determine the ratio of sagittal length to coronal length of the distal tibia for predicting the sagittal length of the distal tibia. A total of 202 ankles were measured based on CT imaging availability. We measured the coronal length (Width, W) parallel to the Chaput tubercle from CT scans. Sagittal length was divided into 3 points (Diameter D1, D2, D3) in the axial plane on the same level. The relationship between coronal length and each sagittal length was determined through correlation analysis. A prediction model was then developed using multiple regression. We also analyzed the quality of the prediction model and validated the prediction model with a validation cohort. Each sagittal length (D1, D2, D3) and coronal length had a significant positive correlation (p < .01). In the prediction model, sex, height, and W were significantly associated with D1, D2, and D3 (p < .05). Prediction models were made for each sagittal length (D1, D2, D3). Concordance correlation coefficient (CCC) values of prediction models for D1, D2, and D3 were 0.78, 0.72, and 0.72 for the derivation cohort and 0.69, 0.63, and 0.61 for the validation cohort, respectively. Accuracies of models as ± 2SD for D1, D2, and D3 were 93.9%, 94.9%, and 94.9%, respectively. This study predicted the sagittal length of the distal tibia for preoperative planning by measuring the coronal length of the distal tibia. Prediction of the sagittal length of the distal tibia can help foot and ankle surgeons fixate screws stably to prevent iatrogenic injury of posterior structures of the distal tibia.