Histomorphologische Untersuchungen zur Frakturheilung unter temporärem Distraktionsreiz

Abstract

Mechanical strain during callus distraction is known to stimulate osteogenesis. The new idea was to use this stimuli to enhance the healing of a normal fracture without lengthening the bone. In this study we stimulated fracture healing by temporary distraction and subsequent reconstruction of the fracture gap. 14 skeletally mature mountain sheep underwent a middiaphyseal osteotomy of the right tibia, stabilized by external fixation with an interfragmentary gap of 3 mm. A custom-made external fixator allowed either a temporary axial distraction (TD-group; n = 6) or a constant fixation (K-group; n = 8). Distraction began 7 days post-operatively with a rate of 0.5 mm twice per day for 2 days and adjacent shortening of 1.0 mm twice on the third day. The procedure was repeated 4 times. Fluorochrome labeling was performed at day 20 (Calceingreen) and day 30 (Tetracycline). After 8 weeks the sheep were sacrificed and healing of the osteotomies was evaluated by histological methods. In order to compare these two groups with a model of classic distraction osteogenesis a third group was analysed (D-group; n = 8). This group had been part of an already finished project. In the fracture gap there was 22 % bone in the TD-group and 2 % bone in the K-group. After completing the distraction protocol there was a significantly higher bone formation rate in the TD-group than in the C-group. In the D-group 40 % bone was found. Temporary axial strain in the osteotomy gap increased callus formation during secondary fracture repair in the gap and at periostal and peripheral sites. This study demonstrated the feasability of fracture healing stimulation by temporary application of mechanical strains.