ANATOMICAL INVESTIGATIONS ON THE KNEE BY MEANS OF COMPUTER-DISSECTION

Abstract

This paper reports an extensive analysis of the articular surfaces of the femur and the tibia in sagittal, frontal and coronal sections, obtained by digitizing the bones with a precise electrogoniometer (FARO Arm) and elaborated off-line fitting the profiles with least square curves. Within the method resolution, we show that the tibio-femoral joint can be described as consisting of two different compartments rigidly connected. The femoral medial side can be represented by an ellipsoid with its main axis in the AP direction, semi-axes equal to 30 and 23 ± 2 mm (posteriorly spherical) and circular ML section with a radius equal to 20 ± 2 mm, which articulates on a (tibial) semi-cylinder with its main axis in the AP direction and conform circular ML section (radius equal 22 ± 1.3 mm). The femoral lateral side can be represented by a ellipsoid with lower eccentricity and a shorter AP size than the medial side, semi-axes equal to 26 and 20 ± 4 mm. It has an elliptic ML section with a sloped major axis parallel to the tibial spine, which forms an angle around 160° with the lateral tibial plateau. This study integrates a previous study by two of the authors with further data on tibia and femur, explaining when the sagittal view of femoral condyles can be better fitted by ellipses than two circles and when it is equivalent. This work represents a systematic numerical study of the tibio-femoral joint in six cadaveric knees, integrates the known anatomical data and provides updated and quantitative 3D information useful for mathematical knee models, prosthesis design, further understanding of knee biomechanics and the function of knee anatomical structures.