SAT-666 - Impact of Body Mass Index Z-Score on Skeletal Maturation Assessment by Bone Age

Bone Age (BA) estimation is an important element in the diagnosis of medical conditions that affect children’s growth, such as hypothyroidism, abnormal puberty, and growth hormone deficiency. Moreover, it can be used as a tool to monitor treatment for growth disorders or delays. It allows clinicians to evaluate the effectiveness of sometimes invasive and often costly treatments and make adjustments accordingly. The estimation of BA with a radiological image of the left hand and wrist describes the degree of maturation of a child’s skeleton. One of the most commonly available standards for the BA estimation is the Greulich and Pyle (G&P) Atlas (1959) [1]. This method involves the visual inspection of X-ray images of a child’s left hand and wrist, followed by comparison with a set of reference images collected from a homogenous limited number of children. Nutritional status is linked to growth rate and skeletal maturating and the clinician has to estimate, with great variability, how much obesity or failure to thrive can advance or delay skeletal maturation, respectively. That estimation can have significant influence on the evaluation, the ordering of tests and the treatment of growth disorders.
Research Strategy: We sought to determine the contribution of adiposity, as reflected by body mass index (BMI) Z-score to the BA estimate in boys and girls of various ancestry. We extracted more than 12,000 X-ray images of BA from the EMR of Michigan Medicine spanning from 2000 to 2022.
Subjects: A total of 12,924 images collected across racial groups, included 1109 Black, 10173 White and 1742 Other, with an average age of 140.7±37.1 months. There were 7508 (58.1%) females and 5416 (41.9%) males with a similar distribution across racial groups. There were 3687 (28.5%) overweight (BMI = or > 85%) and 2178 (16.8 %) obese (BMI = or > 95%) children.

Results: The percentage of overweight was greater in Black children at 41.2% versus 27.5% in Whites and 26.1 % in Other. Out of all the Black children with BA images, 28.5% were obese versus 16.0% White and 14.2 % Other. A subset of 100 images were further analyzed with bone age readings showing a positive association between BMI Z-score and BA (F 3.71, Prob>F 0.0583).

Conclusion: The high prevalence of obesity in children affects growth trajectory and advances the BA. Separating weight-related factors from traditional global BA reading will allow the clinician to refine the evaluation of growth disorders. A predictive value assigned to BMI z-score will provide the clinician with a more nuanced interpretation of the growth trajectory associated with BA. We aim to enhance BA reading by incorporating BMI as a predictor of the degree of BA advancement independent of pathology.
[1] Greulich and Pyle Radiographic Atlas of Skeletal Development of the Hand and Wrist (1959)

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