Growth plates are found at the end of the long bones in the body. The bones get longer as the child grows because of growth at the growth plate. There are rows of cartilage cells in the growth plate that multiply and enlarge during the growth process. The cartilage cells secrete enzymes and are surrounded by a matrix that eventually forms part of the new bone. The cartilage cells eventually die when they run out of nutrients as they get pushed to the edge of the growth plate. As they die, bone forming cells invade the area using the matrix that is already there as scaffolding to create the new bone. This process is called endochondral ossification and without it our bones would stay the same length.
Closure of the growth plates
As long as the growth plate remains open and continues to produce cartilage cells that multiply and expand, the bone will continue to get longer and the child will grow. After puberty, complex signals that are not well understood cause the growth plates to close. There are no more cartilage cells available in the growth plate to multiply and expand and the bone does not get any longer once the growth plate has closed. This process is irreversible.
The growth plates of the different bones of the body normally close at different ages. For example, the growth plates of the humerus (arm bone) typically close around 15 years of age but the growth plate of the radius (forearm bone) may stay open until 22 years of age.
There are many factors that can affect the rate and amount of bone growth in an individual. Illness, injury or severe nutritional deprivation can all cause slowing of the growth process and in severe cases can cause premature closure of the growth plate leading to shorter stature. Some injuries cause part of the growth plate to close while some of it stays open, which can lead to uneven growth of the long bone and subsequent deformity.
Growth plate fractures
Fractures through the growth plate are a concern due to the risk of disruption of the growth process from injury to the cells in that area. There are different types of growth plate fractures depending on which part of the growth plate they involve and if there is extension into the joint at the end of the long bone. All growth plate fractures in children should be reviewed by a specialist, to ensure adequate treatment at the time of injury to prevent permanent injury to the growth plate and growth arrest.
Some growth plate injuries are acute fractures, occurring during the trauma of falls or contact in sport. Other growth plate injuries are slower to progress, build up over time and present as joint pain or a limp that seems to have no cause. One such growth plate injury is a slipped upper femoral epiphysis (SUFE) that is explained further in the section on hip injuries in children and adolescents.
Some growth plate injuries are due to compression of the cells of the growth plate under repetitive loads. This is most common in the growth plate of the wrist in a gymnast. This is known as a distal radius stress injury. Repetitive loading of the wrist in handstand work can compromise the blood supply to the growth plate. This interrupts the calcification and mineralization of the growth plate into normal bone but the cartilage cells continue to multiply and expand so the growth plate actually gets wider and this can be detected on xray. This disruption can eventually lead to premature closure of the growth plate if the load continues. Rest from upper limb weight bearing under the guidance of a specialist experienced in treating this type of injury is advised until the problem resolves, to prevent growth arrest or bony deformity.
If your child has sustained a growth plate injury, a consultation at Shire Sports Medicine can be beneficial to get an accurate diagnosis, to help guide management and to ensure the prevention of further complications.