Abstract
Purpose
In patients with multiple trauma delayed fracture healing is often diagnosed, but the pathomechanisms are not well known yet. The purpose of the study is to evaluate the effect of a severe hemorrhagic shock on fracture healing in a murine model.
Methods
10 male C57BL/6N mice per group (Fx, TH, THFx, Sham) and point in time were used. The Fx-group received an osteotomy after implantation of a fixateur extern. The TH-group got a pressure controlled hemorrhagic shock with a mean arterial blood pressure of 35 mmHg over 90 minutes. Resuscitation with 4 times the shed blood volume of Ringer solution was performed. The THFx group got both. Sham-animals received the implantation of a catheter and a fixateur extern but no blood loss or osteotomy. After 1, 2, 3, 4 or 6 weeks the animals were sacrificed. For the biomechanics the bones were analyzed via X-ray, µCT and underwent a 3-point bending test. The nondecalcified histology based on slices of Technovit 9100. The signaling pathway was analyzed via RT2 Profiler™ PCR Array Mouse Osteoporosis, Western Blot and Quantikine ELISA for RankL and OPG. Statistical significance was set at p < 0.05. Comparisons between groups were performed using the Mann–Whitney U (Fx vs. THFx) or Kruskal-Wallis Test (other groups).
Results
The experiment showed that after 1 week the bones of the Fx- and THFx-mice were macroscopically instable. After 2 weeks the Fx-group showed macroscopically a stable bridging whereas the bones of the THFx-group were partly not stable bridged. 3 weeks after surgery the bones of both groups were stable bridged. Analysis via µCT showed that trauma hemorrhage leads to decreased density of the bone and callus and also to increased share of callus per bone volume after 2 weeks. The 3-point-bending test showed that the maximum bending moment is decreased in the group THFx compared to Fx after 2 weeks. The studies of the histology showed after 2 weeks a decrease in bone and cartilage after trauma-hemorrhage by optical analysis of photographs of the slices. The analyses of the signaling pathway pointed to an involvement of the RankL/Opg and IL6 pathway.
Conclusion
A hemorrhagic shock has a negative effect on fracture healing in terms of reduced density of the bone and callus, increased share of callus per bone volume, decreased maximum bending moment, reduced mineralization of the callus and leads to changes in the RankL/Opg and IL6 pathways.
