2D/3D Planning

Accurate preoperative planning is important in achieving optimal implant placement for target alignment in total knee arthroplasty (TKA). Generally, radiographs and computed tomography (CT) slices are used for two-dimensional (2D) preoperative planning to ensure reproducible intraoperative procedures. However, caution should be exercised because measurements using radiographs and CT slices are affected by limb position and imaging direction due to the internal and external rotation of the lower limbs and flexion contractures. Detailed preoperative measurements using 2D planning is difficult because of one-slice evaluation. In contrast, three-dimensional (3D) preoperative planning can enable a more detailed preoperative planning with the use of 3D analysis software, such as 3D templates and bone models reconstructed from CT scans. 3D planning enables the accurate setting of 3D spatial coordinates according to the TKA surgical technique and detailed planning to reproduce intraoperative osteotomy and implant placement. By implementing an accurate preoperative planning, difficulties experienced during the actual operation, such as “Determination of implant size and cutting bone volume is different from preoperative planning: Do you trust preoperative planning or surgical technique?” In this chapter, specific methods and precautions for 2D planning and evaluation of surgical techniques using 3D planning to achieve mechanical neutral alignment are described.