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Biomechanical consequences of an isolated overload on the human vertebral body
Author(s) -
Kopperdahl David L.,
Pearlman Jonathan L.,
Keaveny Tony M.
Publication year - 2000
Publication title -
journal of orthopaedic research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.041
H-Index - 155
eISSN - 1554-527X
pISSN - 0736-0266
DOI - 10.1002/jor.1100180502
Subject(s) - strain (injury) , context (archaeology) , stiffness , cadaver , vertebral body , compression (physics) , lumbar , anatomy , lumbar vertebrae , bone density , biomechanics , materials science , medicine , composite material , osteoporosis , biology , paleontology
The biomechanical consequences of an isolated overload to the vertebral body may play a role in the etiology of vertebral fracture. In this context, we quantified residual strains and reductions in stiffness and ultimate load when vertebral bodies were loaded to various levels beyond the elastic regimen and related these properties to the externally applied strain and bone density. Twenty‐three vertebral bodies (T11‐L4, from 23 cadavers aged 20–90 years) were loaded once in compression to a randomized nominal strain level between 0.37 and 4.5%, unloaded, and then reloaded to 10% strain. Residual strains of up to 1.36% developed on unloading and depended on the applied strain (r 2 = 0.85) but not on density (p = 0.25). Percentage reductions in stiffness and ultimate load of up to 83.7 and 52.5%, respectively, depended on both applied strain (r 2 = 0.90 and r 2 = 0.32, respectively) and density (r 2 = 0.23 and r 2 = 0.22, respectively). Development of residual strains is indicative of permanent deformations, whereas percentage reductions in stiffness are direct measures of effective mechanical damage. These results therefore demonstrate that substantial mechanical damage—which is not visible from radiographs—can develop in the vertebral body after isolated overloads, as well as subtle but significant permanent deformations. This behavior is similar to that observed previously for cylindrical cores of trabecular bone. Taken together, these findings indicate that the damage behavior of the lumbar and lower thoracic vertebral body is dominated by the trabecular bone and may be an important factor in the etiology of vertebral fracture.