Computational simulation of spontaneous bone straightening in growing children.

Periosteal surface pressures have been shown to inhibit bone formation and induce bone resorption, while tensile strains perpendicular to the periosteal surface have been shown to inhibit bone resorption and induce new bone deposition. A new computational model was developed to incorporate these experimental findings into simulations of spontaneous bone straightening in children with congenital posteromedial bowing of the tibia. Three-dimensional finite element models of the periosteum were used to determine the relationships between the defect angle and the distribution of bone surface pressures and strains due to growth-generated tensile strains in the periosteum. These relationships were incorporated into an iterative simulation to model development of a growing, bowed tibia with an initial defect angle of 27 degrees. When periosteal loads were included in the simulation, the defect angle decreased to 10 degrees after 2 years, and the bone straightened by an age of 25 years. When periosteal loads were not included in the simulation, the defect angle decreased to 23 degrees after 2 years, and a defect angle of 9 degrees remained at an age of 25 years. A "modeling drift" bone apposition/resorption pattern appeared only when periosteal loads were included. The results suggest that periosteal pressures and tensile strains induced by bone bowing can accelerate the process of bone straightening and lead to more complete correction of congenital bowing defects. Including the mechanobiological effects of periosteal surface loads in the simulations produced results similar to those seen clinically, with rapid straightening during the first few years of growth.