BACKGROUND:Hydrolysis in vivo is the key mechanism of degradation in DL-polylactic acid (PDLLA). When it is combined with hydroxyapatite (HA), could the biodegradation and weight loss rate be improved? OBJECTIVE: To observe the changes in the interface and structure of HA/PDLLA composite after in vivo implantation into rabbit femoral defects.DESIGN: Randomized grouping and controlled observation.SETTING: Biomedical Materials and Engineering Research Center, Wuhan University of Technology.MATERIALS: Forty healthy adult Japan White Rabbits of 2.0-2.5 kg, either male or female were provided by the Animal Experimental Center of Hubei Province (No. SCXK. 2003-0005).METHODS: The experiment was conducted in Biomedical Materials and Engineering Research Center, Wuhan University of Technology from June 2005 to March 2006. ①The rabbits were randomly divided into two groups: HA/PDLLA group and PDLLA control group with 20 animals in each group. After anesthetized with ketamine and proazamine, the sample rods of HA/PDLLA and PDLLA were respectively implanted into the drilled bone cavities (φ5 mm × 8 mm) among condyles of femur sites of the rabbits, and the rod could be slightly higher than the surface of bone substance. The samples were covered by periosteum and skin, and then the skin and periosteum were repositioned. ②The complete implants and peripheral bone tissues were taken out respectively after 3, 6, 12 and 24 weeks implantation. The changes in the interface and structure of HA/PDLLA composite after in vivo implantation were observed by using scanning electron microscope (SEM, JSM-5610LV, Japan).MAIN OUTCOME MEASURES: Changes in the interface and structure of HA/PDLLA composite after in vivo implantation.RESULTS: Totally 40 rabbits were involved in the result analysis. After the materials were implanted, HA granules shed from the material surface, some fibroblasts grew into the tissue and a little new osteotylus was formed, indicating HA/PDLLA composite had capabilities of bone-formation and bone-connection. After 24 weeks implantation, the material was divided and wrapped by tissues, neogenetic bone tissue grew into the material, and the fracture healed well,indicating HA/PDLLA composite had good biocompatibility. As for biodegradable PDLLA polymer, hydrolysis in vivo is the most main mechanism of degradation; the degradation speed was decreased owing to being compounded with HA.CONCLUSION: HA/PDLLA composite has capabilities of bone-formation and bone-connection; the biocompatibility of the composite is improved accordingly on account of the decrease of the degradation speed. HA/PDLLA composite is suitable for clinical application as absorbable materials for internal fixation.

Objective To investigate certified specialized nurses' willingness in building an reappraisal system and to provide a basis for further completing the appraisal system and criteria for specialized nurses, defining their roles, and encouraging them to play their leading roles in clinical work.Methods Totally 250 certified specialized nurses from 8 Class Ⅲ hospitals in Beijing were selected by convenient sampling and investigated with the self-designed questionnaire. The subjects' willingness in building the reappraisal system and criteria were analyzed.Results In terms of the 240 specialized nurses' wiliness in building the reappraisal system, their scores in clinical competence, teaching ability and research capability were (13.14±3.86), (13.60±2.27) and (9.50±2.94), respectively. There was statistical difference in the willingness in building the evaluation criteria of clinical competence between specialized nurses with different length of service and titles (P<0.05); there was also statistical difference in the willingness in building the evaluation criteria of teaching ability between specialized nurses with different educational background (P<0.05).Conclusions The specialized nurses' willingness in building the reappraisal indicators. Nursing managers shall train specialized nurses based on their shortcomings, build stricter criteria for future training for specialized nurses, and encourage the nursing team to become expert nurses.