What region of a long bone fuses at the completion of its growth?

The region of a long bone that fuses at the completion of its growth is the epiphyseal plate, also known as the growth plate. This area is made up of cartilage during childhood and adolescence, allowing for the lengthening of the bone. Once growth is complete, typically in late adolescence to early adulthood, the epiphyseal plate ossifies and becomes the epiphyseal line, marking the end of bone growth in length.