Is a bone age of 13 indicative of fused growth plates?

Bone Age of 13 and Growth Plate Fusion Status

A bone age of 13 years does not typically indicate complete growth plate fusion, as most growth plates remain open at this developmental stage, though early fusion may be occurring in some bones.

Growth Plate Fusion Timeline

• Growth plate fusion occurs in an ascending order from the foot to the wrist, with complete fusion happening approximately 2 years earlier in females than males 1
• In females, complete growth plate fusion in most long bones (radius, femur, tibia) typically occurs around age 17, while in males this occurs around age 19 1
• By the time growth plates fuse at the end of puberty, skeletal growth is complete, which typically happens after bone age 13 2

Factors Affecting Growth Plate Fusion

• Sex hormones, particularly estrogens, are essential for growth plate fusion and closure in both sexes 3
• Pubertal development strongly correlates with growth plate fusion score (correlation coefficients between 0.514-0.598 for different growth plate sites) 1
• BMI significantly influences growth plate fusion, with overweight or obese individuals showing increased odds of earlier fusion compared to normal-weight subjects 1
• Physical activity does not significantly correlate with growth plate fusion timing 1

Bone Age Assessment Considerations

• Bone age represents skeletal maturity and is defined by the age in years corresponding to the level of bone maturation 4
• Hand and wrist X-rays are the most commonly used images for bone age assessment, as they reflect the maturation of different bone types 4
• Bone age assessments should be interpreted with caution in patients with certain conditions like achondroplasia 2
• When annual height velocity has slowed to <1.5 cm per year, radiography should be performed to check the status of growth plates; closed growth plates indicate the end of growth potential 2

Clinical Implications

• At bone age 13, most individuals still have significant growth potential as their growth plates remain open 3, 1
• During puberty, radiography should be performed every 1-2 years to confirm growth plates remain open in patients where growth monitoring is clinically important 2
• Bone maturation in females is more advanced than in males at all ages, with females typically being about 2 years ahead in skeletal maturation 3, 1
• Growth plate activity is not constant throughout the growth period; it varies by bone and age 5

Common Pitfalls in Interpretation

• Assuming bone age directly correlates with chronological age can lead to misinterpretation, as various factors including gender, nutrition, metabolic and genetic factors can affect bone maturation 4
• Failing to consider sex differences in growth plate fusion timing may lead to incorrect conclusions about remaining growth potential 1
• Not accounting for the differential growth contributions of proximal versus distal growth plates in long bones can lead to misunderstanding of growth patterns 5