Operative treatment of acute humeral shaft fractures represents a major sou
rce of nonunions. The analysis of the biomechanical and biological causes o
f diaphyseal nonunions of the humerus is a prerequisite for the successful
treatment of ununited humeral shaft fractures. Biologically active nonunion
s heal after debridement and correction of deformities with an improvement
of mechanical stability preferably by fixation with a compression plate. In
atrophic nonunions, the restoration of the biologic capacity to restore os
teogenesis by bone grafting is additionally necessary. The treatment of syn
ovial pseudarthrosis and infected non-union requires removal of bone and de
bridement of synovial and infected avascular tissues, respectively. Intrame
dullary nails to improve mechanical stability and nonoperative treatment wi
th extracorporeal shock waves should only be used in a few special cases wh
ich do not have any severe deformities.