Fig. 5

Schematic diagrams showing the method of measuring the tibial plateau-tibial shaft angle (TPTSA), lateral posterior tibial slope angle (LPSTA), step-off, and condylar widening. The anteroposterior view radiograph (A) shows that the axial line of the tibial shaft and the tangential line of lateral condyle and medial condyle formed the TPTSA (about 92.54°). The LPSTA is measured on the two-dimensional sagittal CT images of the lateral tibial plateau (about 16.58°). In most cases, the cortex of the posterior wall of the lateral tibial plateau was not collapsed. This method can directly measure the LPSTA of the lateral tibial plateau, not the LPSTA of the knee (C) (about 10.77°), i.e., the angle between extending the vertical line of the anterior tibial cortex and the line along the tibial plateau represents the LPSTA on the lateral radiograph of the knee. Step-off was measured on two-dimensional coronal-computed tomography images (D, about 21.54 mm). Line A is the tangent line of the medial tibial plateau, and line B is parallel to line A. Normally, the lateral tibial plateau is about 2–3 mm higher than the medial tibial plateau; in the fracture here, the articular surface collapsed, but the residual tibial spine can be used as a marker to measure the step-off. Condylar widening (E, about 20.75 mm) was measured by first determining the medial margin of the medial tibial plateau and the medial femoral condyle to be in a state of “kissing,” in the largest condylar widening view on two-dimensional coronal-computed tomography images; the greatest articular surface widening of the condylar was measured