Preparation Of Bone Defect Models And Study Of Critical Size Defect In Radius Of Rabbit

Objective:To obtain anatomical data of radius in New Zealand rabbits and establish bone defect nonunion model of radius which periosteum had been retained. To study the critical size defect of bone defect nonunion model in radius of New Zealand rabbits.Methods:1.20 adult New Zealand rabbits were selected. The contours of radius were observed, and the anatomical parameters including the length and the front curvature of radius, the transverse diameters and the sagittal diameters of the middle of radius were measured respectively.2. Select 20 adult New Zealand rabbits to establish bone defect nonunion model of radius, and divide them into two groups of 15mm and 30mm. Bone nonunion was observed by X-ray examination after 4,8,12, 16 weeks. At 16th week the bone nonunion was tested by histological.3. There were 5 groups of adult New Zealand rabbits. In each group, the length of bone defect segment in the middle of radius in New Zealand rabbits was 10mm,15mm,20mm,25mm and 30mm,which was obtained by surgery. The union of bone defect and the number of healing cases were observed by X-ray examination in every 4 weeks, until 16 weeks after surgery. The data were analyzed by SPSS.Results:1.The contours of radius were similar to the ones of human. The related average data are listed as follows:radius length is (70.66±1.91) mm, mid-point diameter is (4.18±0.37) mm, the midpoint of the sagittal diameter is (3.07±0.29) mm, the front curvature of radius is (26.08± 2.54)°, the average weight of the experimental rabbits is (2.88±0.22) kg. The rate of radial midpoint of the diameter ratio and radial length is 5.9% and the rate of the midpoint of the sagittal diameter and the radius bone length ratio is 4.3%. The length of radius was positively correlated with body weight. The transverse diameters and the sagittal diameters of the middle of radius were not correlation with weight, and the transverse diameters was irrelevant with length.2. With periosteum retained, the models that the length of bone defect segment in the middle of radius was 15mm and 30mm were bone nonunion at 16th week after procedure. The bone marrow cavity was blockinged and the bone defect was filled by fiber scar tissue, without any bone tissue, and nonunion.3. When the length of bone defect segment is 35.5-42.2% to the length of radius, and when the length of bone defect segment is 6-7 times to the transverse diameters, the bone defect of radius which periosteum had been retained in rabbits is nonunion.Conclusions:1.This is the first time to observe the anatomical features and the data of radius in New Zealand rabbits. The anatomical parameters including the length and the front curvature of radius, the transverse diameters and the sagittal diameters of the middle of radius may provide credible references for relevant experimental research.2. Bone defect nonunion model of radius which periosteum had been retained in New Zealand rabbits is established successfully.3. When the length of bone defect segment is 35.5-42.2% to the length of radius, and when the length of bone defect segment is 6-7 times to the transverse diameters, the bone defect of radius which periosteum had been retained in rabbits is nonunion. The numerical value is the critical size defect of this bone defect nonunion model of radius, and the data may be significant for the subsequent research of bone nonunion.