Objective To evaluate the antibacterial activity of titanium dioxide-coated screw, and observe its effects on pinhole infection in external fixator treating fractures.

Methods Titanium dioxide-coated screw was prepared, and its antibacterial experiment was performed in vitro.Thirty New Zealand white rabbits were randomly divided into the pinhole group(MO group) and titanium oxide-coated screw group(TG group)(30 rabbits each group).A fracture complicated with pinhole infection model was established.Two groups were treated with taking X-ray, taking photo, harvesting materials for HE staining, culturing bacteria and counting.

Results The bacteriostatic radius in TG group(2.96±2.86)cm was greater that in MO group(33.96±6.10)cm (P < 0.01).The inflammation scores of soft tissue in MO group after 1 d, 1 week and 4 weeks were higher that in TG group(P < 0.05 to P < 0.01).The difference of bacteria count after 1 d of operation between two groups was not statistically significant(P>0.05), which in TG group after 1 week and 4 weeks of operation decreased compared with the MO group(P < 0.01).A large number of inflammatory cells infiltrated, and gradually increased in MO group after 1 d, 1 week and 4 weeks of operation, and a few inflammatory cells infiltrated in TG group.Partial bone tissue with thread destroy absorption in MO group, and pinhole with clear and no damage and absorption in TG group were identified.At the first week, X-ray findings showed that fracture line began to blur in TG group, while fracture line in MO group remained clear.At the fourth week, the fractures in TG group had reached the bony union, and the displacement of the fracture end in MO group was still obvious and did not reach bony union.

Conclusions Titanium dioxide-coated screw has a photocatalytic bactericidal effect, which can effectively prevent the pinhole infection in external fixator treating fracture.