Abstract
Bone is in a continuous state of remodeling whereby old bone is absorbed and new bone is formed in its place. During this process, new formations reinforce the bone in the direction of the dominant stress trajectories through a functional adaptation. In normal aging, the balance between bone resorption and formation can be shifted. How this affects the functional adaptation remains to be investigated. Furthermore, how or whether the bone continues to change beyond the age of 85 is not yet studied in detail. In this study we examined the age-related changes in the cortical and trabecular bone in old age, and assessed whether we can find evidence of the presence of functional adaptation. We measured cortical and trabecular parameters from micro-computed tomography scans of the femoral head extracted from hip fracture patients between the age of 70 and 93 years. A significant decrease in global trabecular bone mineral density (38.1%) and cortical thickness (13.0%) was seen from the 9th to the 10th decade of life. The degree of anisotropy was maintained globally as well as locally in both high and low stress regions. The local trabecular bone mineral density decreased in both high stress and low stress regions between the 9th and 10th decade of life with similar trends. This suggests that the role of functional adaptation in maintaining the bone structural integrity in old age may be limited. This study highlights the need for a controlled clinical trial examining the cause of the continued bone degradation throughout old age.
Highlights
Normal aging is associated with a shift in balance between bone resorption and formation
Between the 9th and 10th decade a significant Tb.bone mineral density (BMD) decrease is seen for the EPC, SPT, APT and PPT regions of 34.2%, 57.0%, 42.2% and 52.8% respectively
There was no significant difference in Tb.BMD between the first two age groups
Summary
Normal aging is associated with a shift in balance between bone resorption and formation. The law of bone remodelling, commonly referred to as Wolff ’s law but more accurately described by Roux[3], asserts that the internal trabecular bone adapts to external loading conditions to maximize its resistance to the principal stress trajectories. It has been hypothesized that, while trabecular elements transverse to the primary load direction may decrease during aging, trabeculae oriented along the principal compressive axis are largely maintained due to functional adaptation. This might make a bone more susceptible to fractures at loading conditions deviating from the main direction, as experienced for instance with a fall on the hip. Gao et al.[11] showed that the mechanical properties in the longitudinal direction deteriorated more quickly than those in the transverse direction
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
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.
