Morphological characteristics of the developing proximal femur: a biomechanical perspective.

INTRODUCTION In contrast to a plethora of studies on the proximal femur in adults, its external and internal morphology in growing children has not been sufficiently analyzed. OBJECTIVE We analyzed changes in external and internal morphology of the proximal femur during growth and development to interpret the links between them and concepts of the human femoral biomechanics. METHODS We assessed external geometry, internal trabecular and cortical arrangement, and bone mineral density (BMD) of the proximal femur in 29 children (age at death from 1 month to 14 years) from archaeological context by using microscopic and radiographic methods. Results The results showed that both the femoral neck width and length increased with age, with the femoral neck becoming more elongated, while the collo-diaphyseal angle decreased. A strong relationship between age and adjusted areal BMD was found, showing continuous increase during childhood. Parallel trabecular pattern at birth changed to mature three distinct trabecular groups (longitudinal-principal compressive, transversal-tensile and randomly scattered) starting from the age of 8 months. In older children the superior and inferior aspects of the femoral neck differently changed with growth, with medial neck having thicker cortex and trabeculae. CONCLUSION In the light of bone adaptation principle, the observed changes in external and internal morphology are governed by mechanical forces acting on the developing femur. Our findings on the development of trabecular pattern and cortical distribution are compatible with recent views on the femoral biomechanics which point out the predominance of compressive stresses in the femoral neck, adaptation to shear stresses, multiaxial loading perspective, prevalence of muscle effects over body weight, and existence of adaptational eccentricity.