抄録
The purpose of this study is to develop a method with which the mechanical properties of the femoral neck in vivo can be quantitatively evaluated. Modal analysis using the FEM (Finite Element Method) was made to investigate the relationship between Young's modulus of the femoral neck and the resonant frequencies of the femur. The configuration of the finite element model was generated from the CT images of an excised femur obtained from a male cadaver. Reduction of the flexural rigidity of the femoral neck was simulated by sequentially decreasing Young's modulus of the neck in the finite element model. The resonant frequency of torsion decreased more acutely than that of lateral bending as Young's modulus of the femoral neck was decreased. On the other hand, sequential transections were experimentally made in the neck of the femur in order to confirm the validity of the results in the model. The resonant frequency of torsion showed an acuter decrease as the depth of transection increased (i.e. with decrease of the flexural rigidity of the femoral neck) than the lateral resonant frequency. The results of the experimental neck transection were consistent with those of FEM analysis. From the observation of animated vibration modes using the FEM, it was found that torsional vibration was accompanied by bending vibration and that an antinode of the vibration was at the femoral neck. A decrease in the flexural rigidity of the femoral neck was thought to have a stronger effect on the resonant frequency of torsion than on that of bending because there was an antinode of the torsion accompanied by bending at the femoral neck. These results suggested that the resonant frequency of torsion could be one of the parameters reflecting the mechanical property of the femoral neck.
