High energy diaphyseal fractures constitute a complicated matter for trauma units and urgent medical and surgical decisions to prompt stabilization of these patients, might leave some skeletal distortions that affect bone union. The objective is to evaluate the safety and efficacy of extracorporeal shockwave therapy (ESWT), as a treatment for patients with atrophic or pseudoatrophic nonunion. Patients and Methods: Case series which included 50 patients with nonseptic and stable nonunion diaphyseal fracture of femur and tibia. They received a defined protocol of up to three high-energy ESWT (10.000 shocks per session). Each patient was evaluated with x-rays or CT between 4 and 6 weeks, to determine the necessity to continue the protocol and obtain data about initial periosteal-endosteal responses and its evolution. We analyzed, semi-quantitatively, the volume of the fracture zone from initial CT using a mathematical method to calculate the volume in cylinders, and confronting this data with Winquist Classification.