Background

It has been known that hydroxyapatite is an outstanding biomaterial in orthopedic surgery and Chitosan is excellent on wound healing, bone formation in rodents and human. We hypothesize that HAp-CS composites will be benefit and the effect could be different according to their mixture ratio in dogs

Aims

The purpose of this study was to investigate therapeutic effects of HAp-CS with different content-ratio in canine bone defect model.

Methods

Five adult beagle dogs were used. Six drill-hole defects a dog were established in long bones, making 30 sites totally. Thirty sites were divided into 5 groups: 2 sham groups (12 sites) and 3 experimental groups (18 sites). The following composites were implanted into experimental groups: gel-formed 100 wt% HAp (HAp100 group), gel-formed 80:20 wt% HAp-chitosan (HAp80CS20 group), gel-formed 60:40 wt% HAp-chitosan (HAp60CS40 group). The evaluations were performed by radiographs obtained biweekly until 10 weeks after surgery, image analysis, bone mineral density and histology.

Results

After 10 weeks, complete healing was observed in HAp100 group. Less complete healing was shown on HAp80CS20, HAp60CS40 and Sham groups in decreasing order. The periosteal reaction of HAp60CS40 group was most aggressive followed by the HAp80CS20 group. The response in HAp100 and Sham groups was scant.

Conclusion

These results suggested that HAp alone is the most effective in healing in this study. Unexpectedly, the lesser the amount of Chitosan mixed with HAp, the better the therapeutic consequence. Further study might be required to reveal the effect of Chitosan on orthopedic treatment in various species.