Factors Affecting Bone Growth

Local Regulation. Given that periosteal bone development is site-specific, whereas systemic hormones and nutrition are blind to structure,⁴ it is clear that local regulation is key to bone growth in width. Genetic heritage seems to have an overwhelming effect on periosteal bone development. Volkman and colleagues,¹⁰⁹ who experimented with various genetic markers in rats, concluded that genetic control of cortical bone geometry is complex and that femoral size and shape may be influenced by different but overlapping groups of polymorphic loci.

Mechanical Regulation. Mechanical forces seem to be very important in determining bone width. For example, the difference in width between femur and humerus can be explained by the different mechanical forces acting on each bone. This perspective is supported by Ruff,⁸² who showed that the correlation of body size (body weight–bone length) and bone strength is stronger in the femur than in the humerus.

The vital role of mechanical forces in bone growth in width is also supported by results of a study by Goodship and colleagues,¹¹⁰ who overloaded the radius of young pigs by partially removing the ulna. They showed that the radius was strengthened by rapid periosteal apposition. This effect has also been noticed in the clinical setting, when the tibia is replaced with the fibula, which quickly hypertrophies in order to resemble the tibia.¹¹¹

Conclusion

Longitudinal bone growth has been extensively studied. Systemic and local hormonal pathways control bone growth in a complicated regulation system. Mechanical loading is also strongly correlated with longitudinal bone growth. Bone growth in width has received less attention. Despite its importance in bone stability, periosteal development—and periosteal apposition and resorption more specifically—has not received enough attention. Researchers need to clarify the role of genetic factors affecting periosteal development.