Abstract
Vertebral fractures associated with osteoporosis are often the result of tissue damage accumulated over time. Microscopic tissue damage (microdamage) generated in vivo is believed to be a mechanically relevant aspect of bone quality that may contribute to fracture risk. Although the presence of microdamage in bone tissue has been documented, the relationship between loading, microdamage accumulation and mechanical failure is not well understood. The aim of the current study was to determine how microdamage accumulates in human vertebral cancellous bone subjected to cyclic fatigue loading. Cancellous bone cores (n = 32) from the third lumbar vertebra of 16 donors (10 male, 6 female, age 76±8.8, mean ± SD) were subjected to compressive cyclic loading at σ/E0 = 0.0035 (where σ is stress and E0 is the initial Young’s modulus). Cyclic loading was suspended before failure at one of seven different amounts of loading and specimens were stained for microdamage using lead uranyl acetate. Damage volume fraction (DV/BV) varied from 0.8±0.5% (no loading) to 3.4±2.1% (fatigue-loaded to complete failure) and was linearly related to the reductions in Young’s modulus caused by fatigue loading (r2 = 0.60, p<0.01). The relationship between reductions in Young’s modulus and proportion of fatigue life was nonlinear and suggests that most microdamage generation occurs late in fatigue loading, during the tertiary phase. Our results indicate that human vertebral cancellous bone tissue with a DV/BV of 1.5% is expected to have, on average, a Young’s modulus 31% lower than the same tissue without microdamage and is able to withstand 92% fewer cycles before failure than the same tissue without microdamage. Hence, even small amounts of microscopic tissue damage in human vertebral cancellous bone may have large effects on subsequent biomechanical performance.
Highlights
Vertebral fractures are the most common form of osteoporosisrelated fractures [1,2]
51% of all vertebral fractures are associated with a discrete loading event, suggesting that many vertebral fractures are the result of tissue damage caused by multiple loading events over time [3,4]
Maximum strain was increased in specimens receiving more fatigue loading, but did not exceed 2% in the groups where cyclic loading was stopped before failure (Groups 1–6, Fig. 3C)
Summary
51% of all vertebral fractures are associated with a discrete loading event, suggesting that many vertebral fractures are the result of tissue damage caused by multiple loading events over time [3,4]. Cancellous bone is the primary load-carrying component in human vertebral bodies, suggesting that damage accumulation and related degradation in biomechanical performance of vertebral cancellous bone is part of the development of vertebral fractures [5]. Microdamage may be stained using radio-opaque contrast agents combined with x-ray computed tomography (micro-CT, etc) [15,16,17]. Relations between a single loading event and the amount of resulting microdamage have been reported [16,24,25,26], but less is known about microdamage accumulation during cyclic fatigue loading
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
