HEALING-PROCESS OF SPIRAL FRACTURES OF TH E SHEEP TIBIA AFTER DIFFERENT TREATMENT METHODS - OSTEOSYNTHESIS WITH INTERNAL-FIXATION, THE INTRAMEDULLARY NAIL, AND A DYNAMIC COMPRESSION PLATE

The healing process of spiral fractures of the sheep tibia was investi gated in an experiment with simulated clinical conditions. The effects of conventional internal fixation techniques with the DCP and the int ramedullary nail are compared with those of internal fixation with the spine fixator. The internal fixation techniques are described in term s of their bending stiffness when mounted on the fractured bone. The i n vivo investigation was documented clinically and radiographically an d the post mortem specimens were evaluated histologically. The bending stiffness of the healed bone was assessed in relation to the contrala teral side. After application of the DCP, primary healing took place a nd extensive transcortical necrosis occcurred in the implant bed. Intr amedullary nailing led to secondary healing and to necrosis of the inn er cortex close to the endosteum. After internal fixation with the spi ne fixator, gap healing took place and no cortical necrosis was observ ed. The clinical course was generally good after all procedures. The h istological evaluation shows that damage to the vascularity of the bon e can only be avoided by using the spine fixator. This principle seems to be appropriate for the purposes of biological internal fixation.