The epiphyseal line the part of the bone that replaces the epiphyseal growth plate in long bones once a person has reached their full adult height. Either rounded end of a long bone is called an epiphysis, and the shaft of the bone is called the diaphysis. The epiphyseal line is the marking that indicates where the two parts of the bone meet and where the epiphyseal plate was once located in children and young adults.
An epiphyseal line is visible on a standard x-ray. It looks like a thin dark streak that stretches horizontally across the rounded ends of the bone. The line may be slightly raised and rougher than the surrounding bone. A person with abnormal bone growth may have a visible crack or an uneven line showing on an x-ray.
Formation of this line takes place over many years. When the growth rate slows down after puberty, the cells stop the process of replication and all bone growth eventually stops. Ossification, the hardening of cells into bone, of the epiphyseal plate occurs when osteoblasts transform the cartilage cells found in the growth plate into bone. Once the entire growth plate is ossified, the epiphyseal line has formed.
The epiphyseal plate is the portion of the bone that is responsible for a bone’s growth in length. It is formed from cartilage cells that are constantly dividing within the growth plate. As the new cells get older, they begin to ossify, or harden, and become part of the bone. Bone growth occurs when the layers of ossified cells build up in size.
Injuries to the epiphyseal plate may cause abnormal bone growth. This may cause early formation of the epiphyseal line and an end to longitudinal bone growth in the affected limb. Fractures that pass through the epiphyseal plate may need to be stabilized with the surgical placement of pins and plates. These may allow the delicate cartilage growth plate to heal and restore the normal pattern of bone growth.
The presence of an epiphyseal line on the long bones can be used to indicate the age of skeletal remains. Only fully grown adults will show evidence of the formation of bone marking. Bones that are not marked with the line can be reasonably determined to belong to an individual that is still growing.
