A CT-based and mechanobiologic model for the simulation of rotation of tibia deformities during patient´s immobilization treatment

Abstract

Tibial torsion deformity produces a change in the alignment of the planes of motion of the articulations of the knee and ankle. Lower limb immobilization by cast is one of the corrective treatments. The objective of this paper was to study the bone remodeling of rotation of tibia deformities during patient´s immobilization treatment. The Finite Element (FE) method was used in the simulation of bone remodeling of the correction process of tibial torsion. A mechanobiologic CT-based FE model of the tibia was defined. An user material subroutine was used to define the bone constitutive material model. Bone density increased its value when the torque was bigger than 12 Nm and it decreased when the torque was lower than 8 Nm. Stress during the iteration process for all load conditions increased. Except for a torque of 4 Nm, the strain decreased its value during the iteration process. At the final iteration step, strain was equal to 0.025 approximately for all load conditions. As it was expected, the variation of bone density during simulation indicates that the bone adapts its structure to load conditions. The bone showed the same density distribution at the end of the simulation for all torque values applied. The highest density was located at the mid-shaft of the diaphysis and at the epiphysis density decreased, adopting a circular ring arrangement.