Abstract:
Daily physiological activities subject our skeletal system to cyclic loading with varying frequencies and mag-
nitudes. These loadings interact with the microstructure of bone and create microdamage, which can cause
stress-induced injuries if not repaired on the time. The early detection is required to prevent the complications
associated with these fractures. In the present study, to examine fatigue loading-induced damage in cortical bone,
the sensitivity of four different indentation devices was investigated. For this, cortical bone samples were
fatigued in four-point bending configuration at 0.5 Hz, 2 Hz and 4 Hz frequencies. Following the fatigue loading,
cyclic reference point indentation (cRPI), impact reference point indentation (iRPI), Vickers microhardness and
nanoindentation tests were performed on the bone samples. Results show that indentation devices are sensitive
to detect fatigue loading induced damage only in 0.5 Hz group samples on compressive region. On the other
hand, the sensitivity of indentation devices for tensile stress-induced damage is not clear. Also, histological
examination of fatigued bone samples shows a significant increase in the crack density and crack length with
fatigue loading only for the 0.5 Hz group samples. The present study provides insight into the sensitivity of
different indentation devices to fatigue loading induced damage, which could be helpful in the development of
new devices for the early diagnosis of stress induced injuries.
