ASSESSMENT OF THE STRENGTH OF PROXIMAL FEMUR IN-VITRO - RELATIONSHIP TO FEMORAL BONE-MINERAL DENSITY AND FEMORAL GEOMETRY

Femoral neck axis length, neck width, and neck-shaft angle mere measur ed on radiographs of right proximal femora from 64 cadavers (28 female , 36 male), Bone mineral density (BMD) was measured using dual energy X-ray absorptiometry (DXA) for various regions of interest, and quanti tative computed tomography (QCT) was used to determine BMD and bone ar eas for cortical and trabecular bone at the trochanter and femoral nec k, The strength of the femur was determined by a mechanical test simul ating a fall on the greater trochanter, and the fracture type (cervica l or trochanteric) was subsequently determined from radiographs. Twent y-six cervical fractures and 38 trochanteric fractures were observed, with no significant sex difference in the distribution of fracture typ es, Femoral strength was significantly elevated in males compared to f emales, DXA trochanteric BMD was more strongly (p < 0.05) correlated w ith femoral strength (r(2) = 0.88) than were any of the other DXA BMD measurements (r(2) = 0.59-0.76), In multiple regression models, a comb ination of different DXA BMD measurements produced only a small increa se (1%) in the explained variability of femoral strength, Of the QCT m easurements, trochanteric cortical area yielded the optimal correlatio n with femoral strength (r(2) = 0.83), Weak, but significant, correlat ions were observed between femoral strength and cortical BMD at trocha nteric (r(2) = 0.28) and neck regions (r(2) = 0.07). In multiple regre ssion models, combining QCT parameters yielded, at best, an r(2) Of 0. 87, Of the geometrical parameters, both neck axis length and neck widt h were significantly correlated with femoral strength (r(2) = 0.24, 0. 22, respectively), but no significant correlation was found between st rength and the neck shaft angle, Combining DXA trochanteric BMD with f emoral neck width resulted in only a small increase in the explained v ariability (1%) compared to trochanteric BMD alone, The results demons trated that DXA and QCT had a similar ability to predict femoral stren gth in vitro, Trochanteric BMD was the best DXA parameter, and cortica l area (not cortical BMD) was the optimal QCT parameter, Geometric mea surements of the proximal femur were only weakly correlated with the m echanical strength, and combinations of DXA, QCT, and geometric parame ters resulted in only small increases in predictive power compared to the use of a single explanatory variable alone. (C) 1997 by Elsevier S cience Inc.