A description of spinal fatigue strength

TY - JOUR

T1 - A description of spinal fatigue strength

AU - Huber, Gerd

AU - Nagel, Katrin

AU - Skrzypiec, Daniel M

AU - Klein, Anke

AU - Püschel, Klaus

AU - Morlock, Michael M

N1 - Copyright © 2016 Elsevier Ltd. All rights reserved.

PY - 2016/4/11

Y1 - 2016/4/11

N2 - Understanding fatigue failure of the spine is important to establish dynamic loading limits for occupational health and safety. In this study experimental data were combined with published data to develop a description of the predictive parameters for spinal fatigue failure. 41 lumbar functional spinal units (FSUs) from cadaveric spines (age 49.0 ± 11.9 yr) where cyclically loaded. Three different levels of sinusoidal axial compression (0-3 kN, 0-2kN or 1-3kN) were applied for 300,000 cycles. Further, published data consisted of 70 thoracic and lumbar FSUs loaded in axial compression for 5000 cycles. Cyclic forces ranged from lower peaks (Fmin) of 0.7-1kN to upper peaks (Fmax) of 1.2-7.1 kN. Based on Wöhler analysis, a fatigue model was developed accounting for three parameters: I) specimen-specific scaling based on the endplate area, II) specimen-specific strength dependency on age or bone mineral density, III) load-specific correction factors based on Fmax and Fmin. The most predictive model was achieved for a combination of Fmax, endplate area and bone mineral density; this model explained 61% of variation (p<0.001). A model including Fmax, endplate area and age explained only 28% of variation (p<0.001). Inclusion of a load-specific correction factor did not significantly improve model prediction of fatigue failure. This analysis presents the basis for the prediction of specimen-specific fatigue failure of the lumbar spine, provided the endplate area and bone mineral density can be derived.

AB - Understanding fatigue failure of the spine is important to establish dynamic loading limits for occupational health and safety. In this study experimental data were combined with published data to develop a description of the predictive parameters for spinal fatigue failure. 41 lumbar functional spinal units (FSUs) from cadaveric spines (age 49.0 ± 11.9 yr) where cyclically loaded. Three different levels of sinusoidal axial compression (0-3 kN, 0-2kN or 1-3kN) were applied for 300,000 cycles. Further, published data consisted of 70 thoracic and lumbar FSUs loaded in axial compression for 5000 cycles. Cyclic forces ranged from lower peaks (Fmin) of 0.7-1kN to upper peaks (Fmax) of 1.2-7.1 kN. Based on Wöhler analysis, a fatigue model was developed accounting for three parameters: I) specimen-specific scaling based on the endplate area, II) specimen-specific strength dependency on age or bone mineral density, III) load-specific correction factors based on Fmax and Fmin. The most predictive model was achieved for a combination of Fmax, endplate area and bone mineral density; this model explained 61% of variation (p<0.001). A model including Fmax, endplate area and age explained only 28% of variation (p<0.001). Inclusion of a load-specific correction factor did not significantly improve model prediction of fatigue failure. This analysis presents the basis for the prediction of specimen-specific fatigue failure of the lumbar spine, provided the endplate area and bone mineral density can be derived.

KW - Journal Article

KW - Research Support, Non-U.S. Gov't

U2 - 10.1016/j.jbiomech.2016.01.041

DO - 10.1016/j.jbiomech.2016.01.041

M3 - SCORING: Journal article

C2 - 26948575

VL - 49

SP - 875

EP - 880

JO - J BIOMECH

JF - J BIOMECH

SN - 0021-9290

IS - 6

ER -