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The measurement of cortical bone is an X-ray absorptiometry estimation method, generally tubular bones of the midpoint of the thickness of the cortical bone and cortical bone index and the measurement technique is easy to learn, can be measured on the old X-ray film, the favor of groups Longitudinal observation and research. Objective: through the study of children and adolescents of the second metacarpal cortical thickness and cortical bone index, explore the different location of the second metacarpal cortical thickness in children and adolescents, a clear process of growth and development of children and adolescents in the second metacarpal cortical thickness and cortical bone index changes in the law, and its north-south regional differences, for the development of children and adolescents of the second metacarpal cortical thickness and cortical bone index standard, a better evaluation of the growth and development of children and adolescents, bone mass change detection in children and adolescents, the prevention of metabolic bone diseases, bone osteoporosis and provide a reference, provide the basis for the impact of sports on the bone mass of children and adolescents. PATIENTS AND METHODS: The study sample reference \Shijiazhuang City. The sample was divided into men's and women's two categories, stratified cluster sampling. 3-19 years 11 258 children and adolescents (male 5588, female 5670) is selected years a group of children and adolescents of all age groups within 15 days after the birth before shooting left wrist before X-ray, the simultaneous measurement of the height , weight. Endpoint to the straight line distance between the distal most bumps vernier caliper measurement of X-ray film in the X-ray film viewer, use the second metacarpal bone at the bottom of a straight line midpoint cross-section of bone width of the second metacarpal transverse diameter (The second metacarpal outer cortical diameter, D), the midpoint of the cross-section of the bone marrow cavity width the second metacarpal ID (The second metacarpal inner both cortical and diameter, d). The calculation of the second metacarpal cortical thickness of the second metacarpal cortical index, second metacarpal cortical thickness of the second metacarpal (The second metacarpal corticalthickness, MCT): transverse diameter - internal diameter of the second metacarpal, MCT = D-d. Second metacarpal cortical index (Thesecond metacarpal cortical index, MCI): the second metacarpal cortical thickness / second metacarpal diameter × 100%, MCI = C / D × 100%. Results: The majority of the age group, the second metacarpal cortical thickness northern boy than a Southern boy, the Northern girls less than southern girl; Southern male and female children and adolescents of the second metacarpal cortical index is greater than the north. Second metacarpal cortical thickness of the north-south regional differences significant age group: 11, 13, 15-year-old boy (P lt; 0.01), girls 3-5 years old, 9-13 years old (P lt; 0.05). 11-16 year-old boys, girls 8-13 years old north-south region of the second metacarpal cortical index significant difference statistically significant (P lt; 0.05). 3-19 years old and the second metacarpal cortical thickness southern boy growth 3.22mm, the northern boy growth 2.97mm; the Southern girl growth 2.64mm, northern girl growth 2.77mm. Substantial growth period of the second metacarpal cortical thickness boys 11-16 years old Southern boy growth rate of 55.90 percent of the total growth of more than 51.85% of the northern boys, Southern boy growing period of 12-16 years mainly in northern boys 13-15 years old, 13-15 years old in northern children and adolescents growth rate (47.81%) is greater than the South (34.16%); growth period of the second metacarpal cortical thickness of the Southern woman 10-13 years old, accounting for 43.64% of the total growth in the northern girls major growth period of 11-14 years old, accounting for 45.13% of the total growth. MCT, MCI not only with increasing age change is also subject to the influence of height, weight. 8-15 year-old man, a woman aged 7-14 MCT height, weight correlation (P lt; 0.05). MCI height has significant age group (P lt; 0.05): the Southern boys 11-13 years old, the northern boys 12-14 years old Southern girl in 5,11,15 years old, 7, 11-year-old northern girl. MCI and body weight was significantly related to age group (P lt; 0.05): Southern boys 12-15 years old Southern girl in 5,12 years old, the North 7, 11-year-old girl; the Northern boy MCI and weight were not statistically significance. Age, height, weight of MCT Multiple regression analysis showed that height regression coefficients were significant (P lt; 0.05): the North and South boys 10-14 years old, southern girl 5-7,9,11 years, the North girls 8 -14 years old. Weight the regression coefficient is statistically significant (P lt; 0.05): Southern boy 8-9 years old, 14-18 years old, the northern boy of 14, 16, 18 years old, the Southern girls 12-17 years old, the northern girls 4-8 years old, 13 -16 years old. Age, height, weight of MCI Multiple regression analysis showed that MCI height regression coefficient was significant (P lt; 0.05): Southern boys 11-13 years old, the northern boys 12-14 years old, southern girl 5,15,17 year-old northern girl 11-14 years old. Weight the regression coefficient is statistically significant (P lt; 0.05): Southern boys 13-16 years old, the north 13-year-old boy, 18-year-old, 16-year-old girl in northern, southern girls weight the regression coefficient is not significant. Research findings: (1) the second metacarpal cortical thickness and cortical index the same height, weight and development indicators, growth gradually with increasing age, the second metacarpal cortical thickness: 11, 13, 15-year-old northern boy than Southern boys (P lt less than Southern girls (P lt; 0.05);; 0.01), 3-5-year-old, 9-13-year-old northern girl second metacarpal cortical index: 11, 13, 15-year-old northern boy than a Southern boy, 12, 14, 16 years old is less than the Southern boys (P lt; 0.05); less than 8-13 years old northern girl southern girl (P lt; 0.05); period of substantial increase in the second metacarpal cortical thickness and cortical index in children and adolescents 10-16 years of age, increase north-south difference. ② MCT, MCI not only grow older changes, is also subject to the influence of height, weight. After eliminating the effect of age, before puberty is mainly Height MCT has a certain effect, enhance the impact of body weight after puberty. By age groups smaller height of MCI, MCI substantially independent of body weight.
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