Mapping the Multi-Directional Mechanical Properties of Bone in the Proximal Tibia

Abstract

The remodeling behavior of bone is influenced by its mechanical environment. By mapping bone's mechanical properties in detail, orthopedic implants with respect to its mechanical properties could stimulate and harness remodeling to improve patient outcomes. In this study, multiaxial apparent modulus and strength of cadaveric proximal tibial bone are mapped and predicted from computed tomography (CT) derived apparent density. Group differences are identified from testing order, subchondral depth, condyle, and sub-meniscal bone with covariates; age and gender. Axial modulus is 50% greater than the transverse modulus. Medial axial modulus is 30% greater than the lateral side. On the lateral side, axial modulus decreases by 50% from proximal to 25 mm distal. On the medial side, axial modulus remains relatively constant. Differences are quantified for density and multiaxial modulus across all subchondral depths, and different power law relationships are provided for each location. Density explains 75% of variation when grouped by subchondral depth and condyle. Yield strength is well-predicted across all test directions, with density predicting 81% of axial strength variation and no differences over subchondral depth. Quantified mapping of bone multiaxial modulus based on condyle and subchondral depth is shown for the first time in a clinically viable protocol using conventional CT.