It is well known that the density and trabecular orientation of cancellous bone adapts to its loading environment . Distribution of the density in the subchondral bone (trabecular bone underneath the joint surface) reflects the loading history of the joint associated with physiological activity. Therefore, trabecular orientation adjacent to the joint surface may reveal the biomechanical function of the joint. This information would be especially beneficial for determining the physiological
loading of the knee joint, where there is a wide range of dynamic loading to the joint surface, and redundant muscle, tendon, and ligament forces are applied. Analysis of the trabecular orientation of the proximal tibia provides the loading history of the tibio-femoral joint following Wolff's hypothesis .
The proximal tibia trabecular structure was analyzed in seven fresh human tibias using the two-dimensional Fourier analysis of contact radiograph images taken from 5-mm sagittal sections (Fig. 14A). Several specific regional differences in trabecular orientation were identified (Fig. 14B). Trabeculae beneath the lateral condyle were oriented toward the posterior cortex and particularly toward the proximal tibio-fibural joint (TF). Beneath the medial condyle, trabeculae were oriented toward both the anterior cortex and the posterior cortex. Trabeculae located immediately below the center of the medial condyle (subchondral bone region) were oriented parallel to the joint surface (S). At the tibial tuberosity, there was a strong orientation (DP) toward the patellar tendon insertion site (PT). Superior to the tibial tuberosity, there were trabeculae oriented in the direction of the patellar tendon insertion surface on the tibial tuberosity. The specific power spectrum of trabeculae beneath the insertion sites of the anterior and posterior cruciate ligaments was also observed.
The distinct trabecular orientation found in the proximal tibia may be adapted to its applied loading, not only at the joint surface but also at the tendon and ligament insertion sites. Mechanical properties of cancellous bone show anisotropy based on trabecular orientation. Distribution of the trabecular orientation in the proximal tibia could be used for material property data for numerical analysis such as a finite element analysis and/or validation of the analysis.
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