gms | German Medical Science

Introduction: The calculation of the ossicles vibration is more exactly with consideration of its deformation. Different measuring procedures for mechanical parameters of the bone involve a certain structure level in each case. In addition to former measurements carried out with the scanning acoustic microscopy and the nanoindentation, the application of the microindentation is presented here. The structural dimension involves parts of osteons with the integration over many lamellas in predominantly axial as well as tangential orientation and areas of light microscopically identifiable skein bone.

Method: On 8 in PMMA embedded, cut and polished probes of ossicles were carried out instrumented hardness tests with the Fischerscope HV100XYp (Fischer, Germany) with Vickers indenter. Single indentations on selected positions and series of equidistant impressions show the distribution of hardness. A maximal force of 1000 mN produced impressions of typical depth of 7 µm and diagonal of 40 µm.

Results: The modulus of elasticity EIT/(1-vs^2) was determined to 16 GPa. The relative standard deviations of the test series of the light-microscopically defined ROI (regions of interest) were between 7 and 15%. Axial indented lamellas (Martens hardness HM 496 MPa and Vickers hardness HV 68 MPa) were significantly (p<5%) softer than skein bone without lamellar structure (HM 593 MPa and HV 84 MPa).

Conclusions: The heterogeneity of the bone can be proven with the microindentation. The low deviation of measured values permit in first approximation the use of median values of the mechanical parameters for calculations of ossicle deformation.