[Healing of spiral fractures in the sheep tibia comparing different methods--osteosynthesis with internal fixation, interlocking nailing and dynamic compression plate].

The healing process of spiral fractures of the sheep tibia was investigated in an experiment with simulated clinical conditions. The effects of conventional internal fixation techniques with the DCP and the intramedullary nail are compared with those of internal fixation with the spine fixator. The internal fixation techniques are described in terms of their bending stiffness when mounted on the fractured bone. The in vivo investigation was documented clinically and radiographically and the post mortem specimens were evaluated histologically. The bending stiffness of the healed bone was assessed in relation to the contralateral side. After application of the DCP, primary healing took place and extensive transcortical necrosis occurred in the implant bed. Intramedullary nailing led to secondary healing and to necrosis of the inner cortex close to the endosteum. After internal fixation with the spine fixator, gap healing took place and no cortical necrosis was observed. The clinical course was generally good after all procedures. The histological evaluation shows that damage to the vascularity of the bone can only be avoided by using the spine fixator. This principle seems to be appropriate for the purposes of biological internal fixation.