[Histopathological changes of three kinds of bone grafts in vivo]

To evaluate the tissue response induced by three kinds of bone transplantation materials implanted in rat so as to provide proper evidence for their clinical application.

Thirty-six healthy mature Sprague-Dawley rat, weighing from 229 g to 358 g, were randomly assigned to groups A and B (n=18). Three kinds of materials were implanted into muscles of rats. Calcium sulfate (CS) granular preparations and allogeneic demineralized bone matrix (DBM) were transplanted into the left (group A1) and right (group A2) thigh muscle pouches of group A. Respectively, whereas xenogenic DBM were transplanted into the left (group B1) thigh muscle pouches of group B and the right (group B2) sites were taken as control without implant. The samples (n=6) were collected to make the observation of gross and histology and to analyze histological score after 2, 4, and 6 weeks.

The gross observation: implanted materials were gradually absorbed at late stage in group A1. No obvious degradation and absorption, but fibrosis of tissues were observed in group A2 and B1. The inflammatory reactions were more severe in groups A2 and B1. In group B2, only the changes of scar were seen at operative site. The histological observation: no obvious inflammatory reactions were seen in group A1, CS were gradually absorbed and completely absorbed at 6 weeks, while fibrosis of tissues increased at late stage. Inflammatory reactions in group A2 and group B1 were alleviated gradually, no obvious absorption and degradation were observed. The different two DBM could induce granulation tissues and bone formation at different sites and secondary fibrosis with no obvious immune response was observed. In group B2, there was an increase in collagen fiber density and angiogenesis at late stage. The scores of inflammatory infiltration were significantly higher in groups A2, B1 than in groups A1, B2 (P < 0.05), and the scores of fibrosis was larger in groups A1, A2 and B1 than in group B2 (P < 0.05).

CS has rapid dissolution and good biocompatibility. It is a good replaceable packing materials of bone defects in some upper limb's or acute bone fracture. Both of two DBM have biocompatibility and osteoinductive potential, which dissolution are very slow. Due to these capacity, they can be served as an ideal materials in treatment of lower limb's bone defect and nonunion.