Fracture stiffness as a guide to the management of tibial fractures.

We have studied the progression of healing in 103 unstable fractures of the tibia. In 76 patients we removed the external fixator once the stiffness had reached 15 Nm/degrees in the sagittal plane. Deformity at the site of the fracture subsequently occurred in four patients. In a further 27, we measured stiffness in several planes and removed the fixator only when the stiffness reached 15 Nm/degrees in each. We found that stiffness in two orthogonal planes may differ widely (maximum difference 9.0 Nm/degrees, mean 4.1 Nm/degrees). There were no failures in the second group. We advocate that fracture stiffness be measured in two orthogonal planes when assessing tibial healing and suggest that values above 15 Nm/degrees in two planes give an indication that it is safe to remove the fixator.