Bone Age in Boys Aged 28 Months — Greulich-Pyle Hand and Wrist X-Ray Reference
Bone age assessment using a left hand and wrist radiograph is a standard method for evaluating skeletal maturity in children. The Greulich-Pyle (GP) atlas provides reference standards derived from healthy North American children, allowing comparison of an individual child’s ossification pattern against age- and sex-matched norms. In boys aged 28 months, this assessment is commonly requested during workup for short stature, growth hormone deficiency, precocious puberty, or other endocrine disorders.
Expected Ossification Centers and Skeletal Findings
At approximately 28 months of age in boys, several carpal and epiphyseal ossification centers are typically present. The capitate and hamate are the earliest carpal bones to ossify, appearing around 3 and 6 months respectively, and are well established by this age. The triquetral ossification center typically appears between 2 and 3 years in boys and may be visible or just emerging at 28 months. The lunate generally appears somewhat later, around 3 to 4 years, and is often absent or just beginning to ossify at this age.
The distal radial epiphysis is typically present by around 1 year of age and should be clearly visible at 28 months. The distal ulnar epiphysis generally does not appear until approximately 5 to 7 years in boys and is not expected at this age. Epiphyses of the metacarpals and proximal, middle, and distal phalanges are typically ossifying progressively during this period, with variable maturation across rays. The scaphoid, trapezium, trapezoid, and pisiform ossification centers are not expected at 28 months in boys.
Clinical Pearls
Skeletal maturation in girls is generally ahead of boys by approximately 2 to 6 months during early childhood, a difference that widens further around puberty. At 28 months, the standard deviation for bone age in boys spans roughly ±6 months, so moderate variation is within the normal range. A bone age significantly advanced beyond 28 months in a boy of this chronological age may suggest precocious puberty, congenital adrenal hyperplasia, or exogenous androgen exposure. Conversely, a notably delayed bone age may raise concern for growth hormone deficiency, hypothyroidism, or constitutional delay of growth and puberty. A key interpretive pitfall at this age is over-reliance on a single ossification center: the triquetral in particular shows wide normal variability in timing of appearance and should not be used in isolation to assign bone age. Clinical correlation with growth velocity, auxology, and hormonal parameters remains essential.
Reference: Greulich WW, Pyle SI. Radiographic Atlas of Skeletal Development of the Hand and Wrist. 2nd ed. Stanford University Press, 1959.
