SKELETAL AGE AS A DETERMINANT OF BONE MASS IN PREADOLESCENT FEMALES

Objective. To evaluate the association between chronological age, skel etal age, pubertal stage, and basic anthropometry with bone mass of th e total body, forearm, and second metacarpal bone in 456 healthy Cauca sian females, aged 8-13 years. Design. Total body and forearm bone mea surements were performed by dual X-ray absorptiometry, while bone mass of the second metacarpal was assessed by radiogrammetry. Skeletal age (SA) was assessed by the FELS method and pubertal stage was self-dete rmined by selecting corresponding illustrations of breast and pubic ha ir development. The C-p criterion was used to select the best multiple regression model containing the subset of independent variables with the least bias and best predictive ability for each of the measured bo ne mass variables. Results. Of all the independent variables, weight, stature, and SA emerged as the most significant predictors for almost all the bone mass variables. Multiple regression models were created b ased on the C-p criterion with the resulting R(2) (adjusted) for bone mineral content of total body, proximal forearm, ultradistal forearm, length of second metacarpal, as well as of total, medullary, and corti cal areas: 0.793, 0.523, 0.390, 0.602, 0.232, 0.073, and 0.264, respec tively. The measured bone variables were also regressed on SA using ei ther quadratic or linear equations, depending on the shape of the cubi c splines used for the best curve fitting. Significant positive associ ation (p<0.0001) of SA and each of the bone variables was noted, the h ighest being with bone mineral density and content of total body (R(2) =0.176, 0.338) and proximal and ultradistal forearm (R(2)=0.216, 0.203 , 0.106, 0.201), respectively, as well as with the length of the secon d metacarpal bone (R(2)=0.339). Chronological age and pubertal stage d id not have statistically significant predictive abilities for bone ma ss variables in the multiple regression models. Conclusions. We conclu de that skeletal age is a powerful determinant of bone mass in childre n. It can be used as the criterion for the selection of a biologically homogeneous population with regard to bone mass. This may be importan t for the design of intervention studies targeting bone mass of childr en and adolescents.