In our laboratory, we have been using an 858 Bionix MTS hydraulic material testing machine (MTS Systems Co., Minneapolis, USA) for bone and biomaterial testing (www.mts.com) (Figure 1). The machine is custom fit with software for test control and data acquisition. A collection of interchangeable hardware for compression, tension and bending, and maintenance of controlled environment is also available for use with the machine.
We perform several types of mechanical tests, e.g. axial compression test, tensile test, three-point bending test, push-out test of metal implant, combined test of cartilage and bone, reduced platen test, and shear test of femur head etc.
Any material with a linear elastic component under uniaxial loading can be described by a proportional relationship between change in load and change in length of the material. During mechanical testing, a force-deformation curve is obtained, and is converted to stress and strain curve using the cross-sectional area of the specimen for normalization of load to stress and the original length of the specimen for normalization of deformation to strain.
Prior to mechanical testing, bone samples are prepared by standard procedures with various saws. These saws include EXAKT Diamond Band Saws (Norderstedt, Germany), Leica SP 1600 Saw Microtome (Wetzlar, Germany) or custom-made Microtome for metal implant sectioning (Leiden, the Netherlands) (Figure 2). In addition, an array of refrigerators and freezers are available for tissue storage.
Figure 1: A photo of the MTS 858 Bionix hydraulic material testing system at the Laboratory. A focus of testing device with extensometer and a testing curve are shown at the right.
Figure 2: A photo of various saws for sample preparation prior to mechanical test
