[Experimental fundamental of secondary osteosynthesis (author's transl)]

The process of fracture healing in rats -- femur shaft fractures stabilised by intramedullary nailing -- immediately after osteotomy of 7 -- 21 days afterwards shows the same morphological picture of events. 40 -- 45 days after stabilisation the fracture repair was in the same stadium of woven bone bridging the fracture gap independent of the date the nailing had been performed, with the exception of those animals which had been stabilised 3 days after the osteotomy; these showed morphological signs of different grades of osteitis. In animals which had had internal plate fixation at different times after fracture the definite date of fixation correlated with the occurrence of osteitis. The later the fracture had been stabilised the more frequently delayed union occurred according to instability. Hence, intramedullary nailing of bone fractures should be done at times before or after the phase of massive cell proliferation and infiltration to prevent infection of the bone. Internal plate fixation is more successful when callous tissue is removed from the fracture gap in order to achieve a close bone reduction.