Human bones change dynamically. For a human, bones usually start to form at the 7th week of the embryonic period and continue to develop until the human has reached skeletal maturity. During this stage of development, the mass, density, morphology, hardness and strength of human bones are constantly changing. There are studies that describe the dynamic changes in bone morphology in each part of the human body from the embryonic period to puberty. For example, the femoral neck torsion angle (FNTA) is approximately 30 to 40 degrees at birth, and the angle gradually recedes to 10 to 15 degrees by early adolescence. Infants have a large femoral neck-shaft angle (NSA), and this angle decreases gradually to an angle common in adults. Recent studies have focused on the physiological and molecular mechanisms by which bones sense, transduce, and respond to mechanical loads and have investigated the effects of aging processes on the relationship between cortical bone properties (such as cross-sectional geometry and bone mineral density) and mechanical function.[1,2]
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