A bone age study is a straightforward X-ray procedure used to assess a child’s skeletal maturity, often referred to as their skeletal age. This measurement reflects how far a child’s bones have developed compared to average standards for children of the same chronological age. It involves taking a single X-ray image and comparing the visible changes in bone structure to reference images.
Clinical Reasons for Ordering a Bone Age Study
Physicians, typically pediatric endocrinologists, order this study to investigate concerns related to growth and the timing of puberty in children. This assessment helps diagnose and manage endocrine and growth disorders that affect skeletal development. A common reason for the study is evaluating a child with significantly short or tall stature.
The test is also frequently used to investigate the timing of sexual development, looking for either delayed or precocious (early) puberty. Sex hormones, along with growth and thyroid hormones, play a significant role in orchestrating bone development, and imbalances can accelerate or retard skeletal maturation.
Monitoring treatment efficacy for conditions like growth hormone deficiency or hypothyroidism is another important application. Changes in bone age over time can show whether a child is responding appropriately to hormone therapy. Furthermore, the results are sometimes used in orthopedics and orthodontics to help time surgical or bracing interventions.
The Standard Procedure for Bone Age Imaging
The procedure is quick, painless, and relies on a single X-ray image, almost always taken of the left hand and wrist. This area is chosen because it contains numerous small bones and growth centers that follow a predictable pattern of appearance and fusion throughout childhood.
The left hand is standard practice to ensure consistency and comparability across different patients and studies. The technologist positions the hand flat on the imaging plate, palm down, and the child must remain still for a few seconds while the image is captured. This single posteroanterior (PA) view is sufficient to reveal the necessary bone structure details.
Once the image is obtained, the radiologist compares the appearance of the bones—specifically the shape, size, and degree of mineralization—to standardized references. The comparison is often made using established tools like the Greulich and Pyle atlas or the Tanner-Whitehouse method.
Interpreting Bone Age Versus Chronological Age
Bone age is a measure of a child’s physical maturation, determined by the state of their skeleton, and is distinct from their chronological age (the time elapsed since birth). Interpretation focuses on the difference between these two ages, which helps predict the child’s future growth trajectory. In a child with typical growth, the bone age generally matches the chronological age within a few months.
The study can reveal two primary discrepancies: a delayed bone age or an advanced bone age. A delayed bone age means the skeleton appears younger than the child’s actual age, suggesting more growth potential remains. This finding is common in children with constitutional growth delay (“late bloomers”) or those with certain hormonal deficiencies.
Conversely, an advanced bone age indicates the skeleton is maturing faster than average, meaning the growth plates may close sooner than expected. This result is sometimes seen in cases of precocious puberty or an overproduction of certain hormones. If the difference between the two ages is greater than two years, it helps the physician determine if an underlying medical condition is present.
The calculated bone age is also essential for predicting final adult height. Using specific calculation methods, the doctor can combine the child’s current height with their bone age to estimate how much they still have to grow before their growth plates fully fuse.
Patient Safety and Preparation
A bone age study uses a minimal amount of radiation, similar to other standard X-ray procedures. The risk associated with this single, low-dose examination is considered negligible. Parents may often remain in the room with their child during the brief exposure while wearing a protective lead apron.
No special preparation is required for the test; the child can eat, drink, and take medication as usual before the appointment. The technician may ask the child to remove any metal objects, such as rings or bracelets, from the left hand and wrist area to ensure a clear image.