Abstract
BackgroundDelayed union or nonunion are frequent and feared complications in fracture treatment. Animal models of impaired bone healing are rare. Moreover, specific descriptions are limited although understanding of the biological course of pathogenesis of fracture nonunion is essential for therapeutic approaches.MethodsA rat tibial osteotomy model with subsequent intramedullary stabilization was performed. The healing progress of the osteotomy model was compared to a previously described closed fracture model. Histological analyses, biomechanical testing and radiological screening were undertaken during the observation period of 84 days (d) to verify the status of the healing process. In this context, particular attention was paid to a comparison of bone slices by histological and immunohistological (IHC) methods at early points in time, i.e. at 5 and 10 d post bone defect.ResultsIn contrast to the closed fracture technique osteotomy led to delayed union or nonunion until 84 d post intervention. The dimensions of whole reactive callus and the amounts of vessels in defined regions of the callus differed significantly between osteotomized and fractured animals at 10 d post surgery. A lower fraction of newly formed bone and cartilaginous tissue was obvious during this period in osteotomized animals and more inflammatory cells were observed in the callus. Newly formed bone tissue accumulated slowly on the anterior tibial side with both techniques. New formation of reparative cartilage was obviously inhibited on the anterior side, the surgical approach side, in osteotomized animals only.ConclusionTibial osteotomy with intramedullary stabilisation in rats leads to pronounced delayed union and nonunion until 84 d post intervention. The early onset of this delay can already be detected histologically within 10 d post surgery. Moreover, the osteotomy technique is associated with cellular and vascular signs of persistent inflammation within the first 10 d after bone defect and may be a contributory factor to impaired healing. The model would be excellent to test agents to promote fracture healing.
Highlights
Delayed union or nonunion are frequent and feared complications in fracture treatment
Impairment of fracture healing is linked to demographic changes in society e.g. the growing proportion of elderly people and causes individual and economic damage [3]
In order to evaluate an applicable in vivo model for local therapeutical targeting, we investigated the impaired healing course of a rat tibial osteotomy with intramedullary stabilization compared to a previously described closed fracture model with regular healing
Summary
Delayed union or nonunion are frequent and feared complications in fracture treatment. Animal models of impaired bone healing are rare. Specific descriptions are limited understanding of the biological course of pathogenesis of fracture nonunion is essential for therapeutic approaches. Ten percent of all fractures require further surgical procedures because of impaired healing [1]. Coles [2] reported up to 17 percent of nonunions after treatment of closed tibial shaft fractures. Models simulating impaired fracture healing in animals are not easy to conduct. Animal models of bony nonunion mainly utilize techniques with large segmental defects, thermic treatment of the defect region, instable fixation or combinations of these procedures [5,6,7,8]
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