Fracture stiffness measurement in the assessment and management of tibial fractures.

Fracture stiffness results obtained from patients with tibial fractures treated with external skeletal fixation are reviewed. A threshold value of bending fracture stiffness at which removal of the external fixator and functional loading of the fracture can be prescribed is proposed to be 15 N m degree(-1). The logarithm of the bending stiffness was found to give a linear relationship with time post-fracture, thus implying that stiffness increases exponentially with time. From three previous studies of mechanical measurements of fracture healing, the fracture stiffnesses at which independent weight-bearing was permitted were determined and were found to be comparable with the threshold value of stiffness proposed in this paper. A review of previously published data for the in-vivo stiffness of intact tibiae showed that the stiffness required for functional healing of a tibial fracture is between 17 and 25% of that of the intact tibia.