Three dimensional strain measurement by image registration technique

Tendons are tough fibrous tissues that facilitate skeletal movement by transferring muscular force to bone. Studies into the effects of mechanical stress on tendons have shown that these can either accelerate healing or cause tendon injuries depending on the load applied. It is known that local strain magnitude and direction play an important role in tendon remodeling and also failure, and different techniques to study strain distribution have been proposed. Image registration and processing techniques are among the recently employed methods. In the present study, a novel three dimensional image processing technique is introduced to study local strain and displacement distribution in tendon. The results shown that, the local normal strain values in the loading axis are smaller than the global applied load and fibers sliding are detected as a dominant mechanism for transferring the applied load within tendon. However, results from different samples suggest twisting or deflection in some cases. The proposed 3D image registration method is essential for analyzing this out of plane movement, which cannot be detected using standard 2D method.