Distal Phalangeal Physeal Closure Preceding Ossification of the Thumb Adductor Sesamoid: A Case Report

Assessment of skeletal maturity is fundamental to pediatric orthopedic practice, as remaining growth potential influences prognosis and treatment decisions. Ossification of the thumb adductor sesamoid is widely used as a pubertal landmark and is expected to precede distal phalangeal physeal closure in established bone age assessment methods. Deviation from this sequence is rarely described. We report a case of distal phalangeal physeal closure occurring in the absence of thumb adductor sesamoid ossification in a patient with growth hormone deficiency.

A 15-year-old female with hypopituitarism and growth hormone deficiency was followed for adolescent idiopathic scoliosis. Despite long-term recombinant growth hormone therapy, she demonstrated delayed pubertal progression. A posteroanterior radiograph of the left hand and wrist obtained to assess skeletal maturity revealed complete distal phalangeal physeal closure across all digits without ossification of the thumb adductor sesamoid. The contralateral hand demonstrated early sesamoid ossification. At a chronological age of 15 years and 4 months, bone age was estimated at 13 years and 6 months, consistent with delayed skeletal maturation. This represents a discordant and atypical sequence of ossification.

This case demonstrates that thumb adductor sesamoid ossification may be absent despite distal phalangeal physeal closure in patients with endocrine dysfunction. Simplified skeletal maturity assessment methods that rely on sesamoid appearance may therefore be misleading in this population. Careful evaluation of the overall pattern of physeal development is essential when managing growth-dependent orthopedic conditions. This report highlights clinically relevant variability in skeletal maturation in the setting of growth hormone deficiency.