High-speed photography of compressed human trabecular bone correlates whitening to microscopic damage

• Published in: Engineering fracture mechanics 2007-08, Vol.74 (12), p.1928-1941
• Main Authors: Thurner, P.J., Erickson, B., Jungmann, R., Schriock, Z., Weaver, J.C., Fantner, G.E., Schitter, G., Morse, D.E., Hansma, P.K.
• Format: Article
• Language: English
• Subjects: Biological and medical sciences; Delamination; Exact sciences and technology; Fracture; Fracture mechanics (crack, fatigue, damage...); Fundamental and applied biological sciences. Psychology; Fundamental areas of phenomenology (including applications); High-speed photography; Medical sciences; Microdamage; Physics; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Skeleton and joints; Solid mechanics; Stress-whitening; Structural and continuum mechanics; Technology. Biomaterials. Equipments. Material. Instrumentation; Trabecular bone; Vertebrates: osteoarticular system, musculoskeletal system
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2006.05.024

Mechanical testing of trabecular bone is mainly motivated by the huge impact of osteoporosis in post-menopausal women and the aged in society in terms of social and health care costs. Trabecular bone loss and impairment of its mechanical properties reduce bone strength and increase fracture risk, especially in vertebrae. It is generally accepted that in addition to bone mineral density, microarchitecture and material properties of bone also play important roles for bone strength and fracture risk. In order to overcome the limitations of standard mechanical tests delivering merely integral information about complicated samples, experiments were designed for step-wise mechanical testing with concurrent imaging of trabecular and cortical bone. In this communication we present an approach for real-time imaging of trabecular bone during compression using high-speed photography and investigate the hypothesis whether the whitening of deformed trabeculae is due to microdamage. Experiments on human trabecular bone samples from a healthy male donor revealed that failure of such samples is highly localized in fracture bands. Moreover, strongly deformed trabeculae were seen to whiten, an effect similar to stress whitening in polymers. Scanning Electron Microscopy of the same regions of interest revealed that whitened trabeculae were strongly damaged by microscopic cracks and mostly failed in delamination. Higher resolution images uncovered mineralized collagen fibrils spanning the cracks. The whitening partially faded after unloading of the samples, presumably due to partial crack closure. Overall, high-speed photography enables microdamage detection in real-time during a mechanical test and provides a correlation to recorded stress strain curves.