Metacarpophalangeal length changes in humans during adulthood: a longitudinal study.

Total lengths of the 19 diaphyseal hand bones were measured from standardized radiographs of healthy American whites as young adults (ca. 21 years) and again at ca. 55 years of age. The four hand-bone rows exhibit distinctive length changes: Distal and middle phalanges continue to increase significantly in length, proximal phalanges constitute a transition zone of little change, and metacarpals uniformly decrease in length. Clear-cut sex differences are noteworthy: Males change more (lose more in some bone rows, gain more in others) than females. Progressive elongation was greatest in the distal phalanges where apposition around the distal aspect ("tufting") is not constrained by a joint or epiphysis. Loss of bone length in the metacarpals by subchondral resorption is consistent with documented reductions in activity levels and grip strength with age, as well as diminished joint spaces which alter loading of the joints.