Effect of initial micro-movement of a fracture gap fastened by composite prosthesis on bone healing

Abstract

Micro-movements are considered to have strong influence on the secondary healing process of fractured long bones, however, the translational shear movement is assumed to have a negative effect on the healing of such fractures. Numerical simulations were carried out with initially applied individual and combined, axial and shear displacements (ranging 0.1 mm to 1.0 mm for a 3 mm fracture at day 1) for a tibial fracture fastened by flexible composite prostheses. The best individual case of healing was seen with an initial axial displacement of 0.1 mm (86% reduced movement compared to the worst, 1.0 mm translational movement) while in combined cases, 0.1–0.1 mm (axial-shear combination) gave the best healing results (0.000157 mm) at day 56. Moreover, using composite intramedullary (IM) nail and bone plate as a superior implant resulted in 157.81% and 201% improved callus volumes with a promising bending stiffness of 20.62 and 19.03 Nm/θ, respectively, at day 154. But the excessive shear movement for the initial 4–6 weeks using an IM nail delayed fracture healing.