Aims: The purpose of the study is to review retrospectively a series of consecutive unstable closed fractures of the humerus in order to evaluate clinical results. Methods: 40 patients affected by closed diaphyseal fractures of the humerus have been treated by Dynamic Axial Fixator (DAF Orthofix). Minimum follow up is two years. Only unstable fractures has been included in the protocol of treatment. Patients affected by uncontrolled diabetes, HIV and psychotic diseases have been excluded. Results were evaluated considering healing time, complications (number and quality), long term clinical results including back to work activity, functional findings and radiographic aspects. Results: Average time of healing is between 10 and 14 weeks. Results were: Excellent: 35; Good: 2; Fair: 2; Poor: 1. Complications were: non-union: 1; replacement of screws: 1; osteolysis of pin track: 4; realignments due to secondary displacement: 3; refracture after frame removal: 1. Conclusions: We believe that this semi-invasive, versatile and well tolerated method may be considered a valid alternative to conservative treatment or to internal synthesis even in case of single trauma, provided a careful selection of patients due to the necessity of close follow up during treatment time.