An Automatic Orientation Method of Tibial Sagittal Plane Based on Anatomical and Statistical Features

Preoperative planning of total knee arthroplasty (TKA) has a significant impact on the quality of the surgery. Nowadays, determining the orientation of the tibia and femur during preoperative planning usually relies on manual implementation by experienced operators, which is complex and lacks of agreement among observers. In this paper, we propose an automatic tibial sagittal plane orientation method to determine the tibial sagittal plane. Based on the statistical information, the position of the axial plane where the tibial tuberosity is located is defined. The lateral border of the tibial tuberosity (lTT) is determined as the farthest point away from the projection point of the mechanical axis in the axial plane. Then the angle between the lTT and the medial third of the tibial tuberosity (m3TT) is calculated according to the anatomical characteristics of the tibial contour. Tibial sagittal plane is determined as the plane which passes through the mechanical axis and the m3TT. For the given tibial model, the result is unique and has the highest repeatability in contrast to other alignment approaches involving manual operations. The average error of our method is -1.9° ± 11.6° compared to the observer's result. This method reduces the cost of manual operation in the preoperative planning process of TKA, whereas the repeatability eliminates the measurement error between multiple operations, and provides an effective reference for preoperative planning.