Manual assessment of fracture stiffness

A fracture stiffness of 15 Nm/degree measured biomechanically has been proposed as a reliable indicator of early fracture union. This study used a fracture model to examine the ability of orthopaedic surgeons to assess the stiffness of a fracture manually. Twenty orthopaedic surgeons were tested along with 20 controls. They each estimated the stiffness of seven rods representing mid-shaft diaphyseal fractures at different stages of healing, and were asked whether the stiffness suggested that union had progressed to the stage where the stabilizing device could be removed. Surgeons were unable to estimate the fracture stiffness accurately, and greatly overestimated rod stiffness particularly for the lower values. This meant that on 83 per cent of occasions when the stiffness was less than 15 Nm/degree, the surgeons considered the fracture models united to a sufficient degree to prescribe removal of the fixator. The results suggest that clinical assessment of fracture stiffness alone may put 83 per cent of patients at risk of refracture or malunion. Manual testing of the mechanical stability of a fracture appears not to be reliable.