Characterisation of the difference in fracture mechanics between children and adult cortical bone

  • Berteau J.-Ph.
  • Pithioux M.
  • Baron C.
  • Gineyts E.
  • Follet H.
  • Lasaygues Ph.
  • Chabrand P.

ART

Clinical literature describes a specific type of children bone fracture, known as “greenstick facture” which is never encountered for adult bone. Concerning children bone, there is a tremendous lack of mechanical references. Indeed, the few studies which explored the mechanical characteristics of growing process in bone dealt with samples close to cancerous cells [1], or with samples from cadavers [2]. These studies gave dispersive results and did not provide insights to the two different kinds of fracture (i.e. brittle for mature bone and plastic for growing bone). Part of the answer could lie in the evolution of the biochemical composition of cortical bone; indeed, Bala et al. [3] have shown that the elasticity depends on the mineral part of the bone matrix and the plasticity on the organic part (collagen 1). This organic part of cortical bone seems to differ between adult and children. Saito et al. [4] have shown that the main non enzymatic crosslinks in mature bone (PYD+DPD) are different from those of growing bone (DHLNL+HLNL). It seems to us that the difference between plastic growing bone fractures and brittle adult bone fractures could be explained by this difference in the non enzymatic collagen crosslinking. We performed three point microbending tests on children and adult bone to evaluate the mechanical Young’s modulus (Em) and the plastic strain energy (ωp). The results are in agreement with the clinical observations. The goal of this study is to explain these differences in mechanical behaviour between children and adult bone by using a biochemical analysis of the organic part quantifying the composition of the collagen.