In vivo determination of homogenised mechanical characteristics of human tibia: application to the study of tibial torsion in vivo.

OBJECTIVE: The study presents a method allowing the in vivo homogenised characteristics of the tibiae of children to be assessed.
DESIGN: Studies have been performed on two groups of children: six normal children, aged from 5 to 16 yr, and on four children, aged from 8 to 11 yr with tibial deformities. We analysed the tibial transverse sections from CT scans performed on the left tibia of each child.
BACKGROUND: Most tibial torsion studies have only been based on geometrical parameters. Our study integrated mechanical and geometrical considerations.
METHODS: The finite element models and integration of mechanical properties were performed from CT scans. Then homogenised mechanical characteristics (tensile stiffness, flexural stiffness and torsional stiffness) were calculated.
RESULTS: The homogenised mechanical characteristics decrease between 20 to 80% of the tibial length. The values increased with age for both groups of children. Children with abnormalities seem to have values of tibial rigidities comparable with those of normal tibiae.
CONCLUSIONS: By considering the mechanical and geometrical properties of the tibia in our study, we showed that the bone stiffness of children is not altered with torsional deformities. RELEVANCE: Torsional tibial abnormalities of children are a frequent phenomenon which may have important consequences on gait and joints. The method developed could be used as an objective assessment of bone rigidities for analysing tibial disorders such as torsional abnormalities of varying severity.