The device performs reference point indentation without a reference probe. The indentation distance is measured relative to the instrument which remains substantially stationary during the impact process, which occurs on the order of one millisecond. In one embodiment, an impact motion with a peak force of order 28N creates an indentation in bone with a depth of approximately 150 mum during which the instrument case moves less than 1 mum. Thus the error in measuring indentation depth due to the motion of the case is less than 1%, making a reference probe unnecessary. Further, this "error" is consistent and can be corrected. In one embodiment, the device measures the fracture resistance of hard tissues by actually creating microscopic fractures in the hard tissues in a measured way. It creates these microscopic fractures by impacting the sample with a sharpened probe. The indentation distance in the sample is correlated with fracture resistance.
