BACKGROUND:Large bone defect caused by various reasons has been a difficult problem in clinical practice. To establish a standard experimental animal model of critical bone defects has vital significance for evaluating the efficacy of bone osteogenesis using various materials and techniques.
OBJECTIVE:To establish the rabbit model of parietal critical bone defects and to determine the diameter of the critical defects of parietal bone in limited time.
METHODS:10 New Zealand white rabbits were selected. The skul seam was treated as the boundary. Four ful-thickness round defects of bone in the parietal bone were made, with diameters of 4, 5, 6 and 7 mm, so as to establish rabbit models of parietal critical bone defects. Gross anatomical observation, X-ray and cone beam CT were used to determine the bone density in the new bone defect area. The healing of bone defects was evaluated by histological examination.
RESULTS AND CONCLUSION:After 12 weeks, the 4 mm group showed high bone healing capacity significantly, and part of the bone bridge had been connected completely. Quantitative analysis of bone mineral density revealed that gray value at defect site and trabecular bone area at the same magnification and the same vision in the 4 mm group were significantly higher than the other three groups (P<0.001). Only a smal amount of new bone in the periphery of bone defects appeared in the 5, 6 and 7 mm groups. The center of defect site was mainly fil ed by fibrous connective tissue. The results confirmed that this study successful y established rabbit models of parietal critical bone defects. During the 12 weeks of observation, bone defects with a diameter of ≥ 5 mm could not be self-healed, which was conformed to the criteria of critical defects of bone, and could be used as a reference value for critical parietal bone defects of a rabbit.

Objective To compare the osteogenesis effect of platelet-rich fibrin (PRF) and platelet-rich plasma (PRP) and investigate the methods of repairing bone defect with PRF.Methods Four defects measuring 7 mm in diameter were made in the parietal bone of 16 New Zealand white rabbits.The defects named A,B,C,and D and were filled with PRF,PRF-mixed Bio-Oss (BO),PRP-mixed BO,and PRP separately.Every four rabbits were sacrificed at postoperative 2,4,8,and 12 weeks and defects were examined grossly,radiographically,and histologically.Besides,bone mineral density and bone trabecular area were determined and expressed as gray-scale values.Results Newly regenerated bone appeared at all defect areas at postoperative 2 weeks.Thereafter,more bone formations were observed over time and area B demonstrated the best bone healing followed by area C,A,and D in succession.Bone trabecular area in areas A,B,C,and D was 10.95 ± 0.58,15.45 ± 0.79,10.22 ± 0.43,and 6.58 ± 0.64 at postoperative 2 weeks with significant differences in pair comparison (F =22.869,P ＜0.01),followed by some increase at postoperative 4 and 8 weeks.Whereas,bone trabecular area in areas A,B,C,and D increased largely at postoperative 12 weeks (35.09 ± 0.58,59.44 ± 0.60,50.75 ± 1.56,and 30.94 ± 1.19) and showed significant difference when compared in a pair (F =1 002.904,P ＜ O.01).Conclusion PRF is superior to PRP in promoting bone formation,but a much better effect of PRF/BO composite is observed in bone repair.

Bedside ultrasound plays an important role in the evaluation of critically ill patients. In order to standardize the application of bedside ultrasound, Chinese Research Hospital Association of Critical Care Medicine and Nursing Research Group of Chinese Research Hospital Association of Critical Care Medicine organized the experts in related fields in China to analyze, discuss and summarize the following contents: ① bedside ultrasound assessment of lungs; ② bedside ultrasound -guided nutrition tube placement; ③ bedside ultrasound assessment of gastric residual volume; ④ bedside ultrasound -guided endovascular catheterization. Finally, the Evidence-based nursing expert consensus on adult bedside ultrasound was formulated.