Morpho-mechanical analysis of porcine growth plate tissue mechanics under torsional shear

Torsional loading of the growth plate occurs in daily activities and sports and is associated with growth plate fractures. This study aimed to investigate the microstructural and mechanical properties of growth plate tissue under torsional loading, focusing on variations across individuals, growth plate types, and anatomical locations. A total of 140 samples from three distinct growth plates in five porcine subjects were subjected to cyclic torsion tests followed by ultimate failure testing. Additionally, histological analyses were performed using Movat's pentachrome staining to assess tissue structure. Mechanical testing revealed significant differences in shear moduli across growth plate types; notably, the proximal femur exhibited a higher primary shear modulus compared to both the distal femur and proximal tibia. Correlation analyses showed a negative relationship between hypertrophic zone thickness and primary shear modulus (ρ=-0.47 at 0.5°/s, p<0.001), as well as between cell column angle and secondary shear modulus (ρ=-0.43 at 0.5°/s, p=0.015). This study provides essential insights into the mechanical behavior of growth plates and how structural variations influence their response to loading, aiding in the development of more accurate computational models.