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Cortical bone development in black and white South African children: iliac crest histomorphometry
C M Schnitzler1, J M Mesquita, J M Pettifor
1MRC Mineral Metabolism Research Unit, University of the Witwatersrand, Johannesburg , South Africa. cmsch@mweb.co.za
Insights
Black children have denser bones than white children, with thicker cortices and endocortical walls, potentially explaining lower fragility fracture rates. These structural bone differences are evident from childhood, suggesting early developmental influences.
Area of Science:
- Orthopedics
- Human Anatomy
- Pediatrics
Background:
- Fragility fracture incidence is lower in Black (B) individuals compared to White (W) individuals in South Africa across all age groups.
- Previous studies in adults suggest histomorphometric differences in iliac crest cortical bone contribute to this disparity.
- No comparative data exists for Black and White children regarding these bone characteristics.
Purpose of the Study:
- To investigate and compare the histomorphometric properties of iliac crest cortical bone in Black and White children.
- To determine if structural bone differences observed in adults are also present in children.
- To explore potential factors contributing to lower fragility fracture rates in Black children.
Main Methods:
- Routine histomorphometry was performed on iliac crest cortical bone samples.
- Samples were obtained from 57 Black and 56 White children aged 0-23 years.
- Analysis focused on cortical thickness, endocortical wall thickness, canal number, cortical porosity, osteoid thickness, and bone turnover markers.
Main Results:
- Growth effects on cortical bone were similar in both groups until age 15.
- Black children exhibited continued increases in cortical thickness and endocortical wall thickness with age, unlike White children.
- After age 11, Black children had fewer canals and a tendency towards lower cortical porosity compared to White children.
- Greater osteoid thickness in Black children may indicate enhanced osteoblast activity and contribute to a structural advantage.
Conclusions:
- Black children demonstrate greater osteoid thickness, endocortical wall thickness, and cortical thickness, with lower porosity compared to White children.
- These bone structural differences in childhood may underlie the lower rates of fragility fractures observed in Black children.
- Environmental and genetic factors likely play a role in these observed disparities.
Unlabelled:
Fragility fracture rates in South Africa are lower in blacks (B) than in whites (W) both in adults and in children. In adults this difference may in part be explained by histomorphometric findings in iliac crest cortical bone of B of thicker, less porous cortices, greater endocortical (Ec) wall thickness, fewer canals and greater osteoid thickness accompanied by greater mineral apposition rate and bone formation rate compared to W. Since no comparative data for B and W children are available we examined iliac crest cortical bone of 57 B and 56 W aged 0-23 yrs by routine histomorphometry.
Results:
The effects of growth as expressed in differences between external and internal cortex were similar in B and W children. Cortical thickness increased with age similarly in B and W until about age 15 whereafter it continued to increase only in B. Ec wall thickness rose with age in B but did not change in W. After age 11 canal number was lower in B. Cortical porosity was highest between ages 6 and 15 with a tendency to lower values in the external cortex in B. Thus structural differences reported in adults were evident in children. Bone turnover as reflected in osteoid surface and eroded surface declined with age similarly in B and W but osteoid thickness did not change with age. Greater osteoid thickness in B children could reflect greater vigor of osteoblasts and greater osteoblast team performance as it did in B adults and may have contributed to the structural advantage in B children.
Conclusion:
B children showed greater values for osteoid thickness, endocortical wall thickness and cortical thickness, and a tendency to lower porosity compared to W children. These features may contribute to lower fragility fracture rates in B children. Differing environmental influences and possibly genetic effects may play a role.
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