Final answer:
The femur head fuses to the shaft between the ages of 14 to 17 years. Epiphyseal plates, visible in radiographs, are an indicator for this fusion, with their disappearance signifying maturity of the bone.
Step-by-step explanation:
The femur head fuses to the shaft during adolescence, with the process being complete between the ages of 14 to 17 years. In terms of skeletal development, large bones like the femur have several secondary ossification centers that appear at different stages after birth. For the femur specifically, the lesser trochanter fuses first at around 11 years of age, followed by the greater trochanter around 12 years of age. Knowledge of these timelines is crucial in interpreting radiographs, where the epiphyseal plates appear dark compared to the ossified bone. A radiograph can identify whether these plates have disappeared to help estimate the age of the individual. For example, the disappearance of the epiphyseal plate at the femur head is an indication of skeletal maturity and an approximate age of 14-17 years.