Portal de Periódicos da CAPES

DENSITY-BASED LOAD ESTIMATION PREDICTS ALTERED FEMORAL LOAD DIRECTIONS FOR COXA VARA AND COXA VALGA

1999; World Scientific; Volume: 03; Issue: 02 Linguagem: Inglês

10.1142/s0218957799000105

1793-6497

Kenneth J. Fischer, F. Eckstein, Christoph Becker,

Hip disorders and treatments

Quantifying differences in joint loading for coxa vara and coxa valga is important for understanding what constitutes a pathological deformity. Prior free-body analyses for varus and valgus femora suggest that the loading direction in single-leg stance becomes more vertical for coxa valga and more horizontal for coxa vara. The objectives of this study were: 1) to apply a density-based load estimation technique to varus and valgus femora; 2) to infer potential differences in femoral loading for varus and valgus femora from the density; and 3) to compare the results with previous studies of femoral loading for single-leg stance. Representative valgus, normal, and varus femora from male cadavers were scanned in the plane of the femoral neck using computed tomography. A two-dimensional finite element model, including the density data from the CT scans, was constructed for each femur. A density-based bone load estimation method was used to determine the dominant loading pattern, and an average load direction was calculated. The average load direction varied consistently from more vertical for coxa valga to more horizontal for coxa vara. The results indicate that the differences in loading directions reduce the risk of epiphyseal slip or neck fracture in coxa vara and increase the tendency for subluxation or dislocation in coxa valga. Agreement between relative load angles from the density-based load estimation and free-body analyses confirms that internal femoral density is adapted to applied loads regardless of external femoral geometry.