Fig. 3

Showing the measurement of sagittal parameters. A, line 3 is the anterior of femur, line 2 is the posterior of femur, line 1 is the tangent line of posterior condylar and parallel to femur shaft. D1 is the distance between line 1 and line 2, D2 is the distance between line 1 and line 3. The posterior condylar offset ratio is calculated as D1 divided by D2. Insall-Salvati index is the value of the length of patellar(D3) divided by the distance between lower poler of the patellar and the tibial tubercle(D4). B, line 1 is the axis of the femur, line 3 is the parallel line of internal surface of the femoral component, line 2 is the perpendicular line of line 3. The angle between line 1 and line 2 is the femoral sagittal angle. Line 4 is the mechanical axis of tibia, line 5 is the tangent line of tibial component surface, line 6 is the perpendicular line of line 4. The angle between line 5 and line 6 is considered as the posterior tibial slope angle