EFFECTS OF AGE, DENSITY, AND GEOMETRY ON THE BENDING STRENGTH OF HUMAN METATARSALS

In this basic study, we investigated the relative roles of donor age, bone density, and bone geometry in determining structural strength of human metatarsals tested in a four-point bending configuration. Densit y measurements were made noninvasively using dual energy x-ray absorpt iometry, and geometric measurements were made by digitally imaging cro ss-sections of specimens. Correlations between area bone mineral densi ty and metatarsal strength were strong (r(2) = 0.83, 0.81 for second a nd third metatarsals, respectively) and were not improved by including cross-sectional area or minimum moment of inertia in multiple regress ion analyses. Increased donor age was associated with decreased bendin g strength (r(2) = 0.51 and 0.45, respectively), which was expected be cause increased age correlated significantly with decreased bone densi ty (r(2) = 0.69 and 0.80, respectively). These results indicate that t he strength of human metatarsals generally decreases with age and that this decrease is likely attributable to decreased bone density. Moreo ver, the results indicate that noninvasive dual energy x-ray absorptio metry measurements of metatarsal density are useful for assessing meta tarsal strength and that additional measurements of bone geometry are not required.