Growth plates are specialized areas of developing tissue found in the bones of children and adolescents. These structures are instrumental in determining an individual’s final height and bone length as they mature. They serve as the primary sites where new bone is generated, allowing the skeleton to expand during the years of growth.
Understanding Growth Plates
Growth plates, scientifically known as epiphyseal plates or physes, are composed of hyaline cartilage. This tissue is located at the ends of long bones, where it facilitates longitudinal bone growth. The process involves cartilage cells, called chondrocytes, undergoing continuous division. These newly formed cells then push older cells away from the growth plate, towards the center of the bone shaft. As these older cells degenerate, they are replaced by bone cells in a process known as endochondral ossification, leading to the lengthening of the bone.
Location in the Human Body
Growth plates are primarily situated at the ends of long bones, which are those longer than they are wide. Examples include the femur (thighbone), tibia and fibula (lower leg bones), humerus (upper arm bone), radius and ulna (forearm bones), and the small bones of the hands and feet (phalanges). Each long bone typically possesses at least two growth plates, one near each end. While most prevalent in the limbs, growth plates are also present in other parts of the skeletal system, such as the spine and pelvis.
Approximate Number and Closure
There is no single fixed number of growth plates in the human body, as the exact count can vary slightly among individuals. A growing skeleton contains numerous growth plates, often described as dozens or even hundreds, given that most long bones have two. The growth plates remain active throughout childhood and adolescence, continually producing new bone tissue.
This process of lengthening eventually concludes through a phenomenon called growth plate closure, or epiphyseal fusion. During closure, the cartilage of the growth plate is entirely replaced by solid bone, forming an epiphyseal line. Once a growth plate closes, that particular bone can no longer increase in length. The timing of this closure varies, influenced by factors such as sex and individual development. In girls, growth plates typically close between 13 and 15 years of age, with most completing fusion by 16 to 18 years. For boys, closure generally occurs between 15 and 17 years, with most completing by 19 to 20 years. Different growth plates within the same individual also close at varying times, following a general sequence.
Implications of Growth Plate Injuries
Growth plates are softer and more vulnerable than the surrounding bone, making them susceptible to injury in children and adolescents. Fractures that involve the growth plate are known as Salter-Harris fractures, and they are a specific concern due to their potential impact on future bone growth. These injuries are common, accounting for 15% to 30% of all fractures in children, often occurring in the wrist, fingers, and lower leg.
If a growth plate fracture is not properly diagnosed and treated, it can lead to complications such as altered bone growth, which might result in a limb that is shorter, longer, or crooked compared to its opposite side. Severe injuries or those left untreated can even cause premature closure of the growth plate. Prompt medical attention and careful monitoring are important to minimize long-term issues.