Animal experiments to examine the histology of fracture healing in osteosynthesis with external fixation and compression.

Tibia osteotomies in sheep were stabilized in nail-fixed and wire-fixed external devices with static longitudinal compression. During the 8-week study programme the mechanical situation of the osteotomies was checked via continuous measurements of interfragmentary tension, used as a functional indicator of stabilization. Simultaneously the test animals were marked by polychromatic fluorescent pigments. The histological findings made at the site of osteotomies showed that the temporal and local progress of ossification was influenced by the degree of stability of osteosynthesis. Under stable osteosynthesis conditions primary bone healing occurred analogous to findings in flattened experimental shaft fractures. On grounds of varying stability performance of external pressure osteosynthesis differences in secondary healing of osteotomies were observed due to interfragmentary instability.