Today’s Children Reach Bone Maturity Earlier, Study Reveals

Children born in the most recent century have bones that reach full maturity earlier – by nearly 10 months in girls and nearly seven months in boys, according to a study recently published in Clinical Orthopaedics and Related Research.

Researchers led by Dana Duren, PhD, director of orthopaedic research at the Thompson Laboratory for Regenerative Orthopaedics at the University of Missouri in Columbia, point out that the timing of epiphyseal fusion (EF) in the bones of the hand and wrist corresponds to late stages of skeletal maturation and signals the end of longitudinal growth. “As such,” the authors write, “assessments of EF status provide a simple means for insight into skeletal development status when evaluating children with disorders such as idiopathic scoliosis, leg length inequality, or constitutional growth delay.”

The authors continue: “We, therefore, sought to answer the following questions: (1) Do children today initiate the process of EF in the hand and wrist earlier than past generations on which maturity standards are based? (2) Do children today complete EF in the hand and wrist earlier than past generations on which maturity standards are based?”

The researchers assessed the radiographs of more than 1,000 children born between 1915 and 2006. The team evaluated radiographs of the bones in the hands and wrists to determine the precise timing of the beginning and ending of a developmental process called epiphyseal fusion.

“We focused on epiphyseal fusion because it signals the end of the growth of the bone,” says Duren. “It begins when the growth plate, which is cartilage at the end of the bone, starts to connect the epiphysis, or bone cap, to the long bone through small calcifications. Eventually, the growth plate completely calcifies and attaches, or fuses, to the long bone. When fusion is complete, so is the growth of that bone.”

The research team used radiographs gathered in the Fels Longitudinal Study, which is the world’s only century-long study of human growth and development, to track when fusion started and when it was complete in children born as far back as 1915. The results showed that the skeletons of children born in the 1990s are reaching fusion completion, and thus skeletal maturity, faster and sooner than children born in the 1930s.

These findings directly impact the timing of the clinical care of certain pediatric orthopaedic conditions, such as leg-length differences, scoliosis and the timing of using growth hormone.

“Our findings show there is a ‘new normal’ for timing when kids’ skeletons will reach full maturity,” says Duren.

Mel Boeyer, MS, predoctoral orthopaedic research fellow and co-author of the study, works closely with pediatric orthopaedic surgeons to understand how physicians time this care.

“The timing for the treatments of these conditions is a critical component to a good outcome,” said Boeyer. “What this research shows us is physicians will need to start looking for the beginning of epiphyseal fusion sooner than they once thought.”

The study does not address what might be the cause of this new normal. However, Duren and many of her colleagues think an increase in exposure to environmental hormones and hormone mimickers could be a contributing factor.

Based on their findings, the authors conclude: “In general, EF [initiation] traits exhibited greater changes in age than did EF [complete] traits with the magnitude of the observed trends appearing to be larger in females than in males. As the contemporary population shifts the timing of maturational milestones, expectations regarding the average age of occurrence for a maturational milestone, including EF, must shift as well.”

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