Lateral radiograph ankle arthrodesis.Lateral ankle radiograph with the measurement of the sagittal tibiotalar angle (STTA). The STTA is the angle between the the two axes A and B. A = longitudinal axis of the tibia, created by connecting two points in the middle of the proximal and the distal tibial shaft (according to method B). B = axis of the talus, defined by a line drawn from the inferior aspect of the posterior tubercule of the talus to the most inferior aspect of the talar neck.