Strong similarities in the creep and damage behaviour of a synthetic bone model compared to human trabecular bone under compressive cyclic loading

A combined experimental and computational study of mechanical properties after balloon kyphoplasty

“…Specimen stiffness showed the highest degree of variation at 21.7% for the kyphoplasty and 13.5% for the untreated specimens respectively, consistent with previous studies of the synthetic bone model. 37 Computational model results for the static response in Table 1 show simulation predictions within the range of standard deviation for the experimental data. Consistent with the experimental observations for increases in stiffness and strength, simulation results similarly predict increases by factors of 2.07 and 1.54 after kyphoplasty.…”

“…A commercially available open cell polyurethane foam which has previously been found to share comparable mechanical and morphological characteristics to human trabecular bone was utilised for the study. 37,38 Consistent with the composite nature of real trabecular bone, the foam model comprises a network of ;400 mm diameter polyurethane struts reinforced with glass fibres ;10 mm in diameter. Two 0.12 g/cm 3 foam blocks (Sawbones Ò product number 1522-507) were prepared in accordance with the procedures described in a previous study.…”

“…Two 0.12 g/cm 3 foam blocks (Sawbones Ò product number 1522-507) were prepared in accordance with the procedures described in a previous study. 37 Fourteen cylindrical specimens in total were extracted from the two blocks and were then randomly assigned to the kyphoplasty (n = 7) or untreated control (n = 7) groups accordingly.…”

“…Physiologically relevant cyclic loads for the fatigue tests were assigned based on a previously outlined protocol to approximate loads experienced while walking up stairs two at a time. 37,42 Applying this protocol results in a load range of 13.4%-52.6% of the ultimate static strength for each specimen using a sinusoidal waveform at a frequency of 2Hz. 37,[43][44][45] The criteria for fatigue failure was set as a 40% reduction in peak-topeak secant modulus of the cyclic loading hysteresis loop compared to the stiffness of the first loading cycle 'E 0 '.…”

“…37,42 Applying this protocol results in a load range of 13.4%-52.6% of the ultimate static strength for each specimen using a sinusoidal waveform at a frequency of 2Hz. 37,[43][44][45] The criteria for fatigue failure was set as a 40% reduction in peak-topeak secant modulus of the cyclic loading hysteresis loop compared to the stiffness of the first loading cycle 'E 0 '. 45 A final end of test condition was defined to approximate a two month period of daily activity up to 333,334 loading cycles 46 or when the total strain reached 20%.…”