Continued Metacarpal Cortical Bone Growth in Mid to Late Adolescence:

A Longitudinal Study of Cortical Bone Acquisition in Documented Sample of 16- to 20-Year-Olds

Maris A. Schneider and Rebecca J. Gilmour

Objectives: Metacarpal radiogrammetry is widely used by anthropologists and archaeologists to assess cortical bone loss. However, the dynamics of metacarpal cortical bone acquisition, as it relates to epiphyseal fusion during late adolescence, requires greater clarification. This research uses the Burlington Growth Study, a longitudinal dataset of digitized hand-wrist radiographs from a known age and sex sample, to investigate cortical bone growth in the second (MC2) and third (MC3) metacarpals of adolescents aged 16–20 years old.

Materials and Methods: Medullary widths (MW), total widths (TW), and cortical indices (CI) of fully fused MC2 and MC3 bones were measured on digitized radiographs for 54 individuals (28 females, 26 males). Cortical bone thickness changes at the periosteal and endosteal margins were quantified and compared over the four-year period from ages 16–20.

Results: CI increased in the MC2 and MC3 of both sexes, indicating continued bone apposition after fusion. With the exception of female MC2s, this change is predominantly located at the periosteal surface (marked by an increasing TW). Cortex growth slows around 18 years old, with no significant changes in CI, TW, or MW between the ages of 18 and 20.

Discussion: In the MC2 and MC3, cortical bone continues to grow in thickness in the years immediately following epiphyseal fusion. Skeletal maturity of these elements, as represented by fusion, does not equate to the cessation of cortical apposition. These findings contribute insight into bone development at the adolescent-adult age transition and specifically serve to refine radiogrammetry age-based inclusion or categorization criteria.