Abstracts Category : Other

Cortical porosity - Its regulation and association with fracture

by Daniel Sundh

Objective: Osteoporosis is a disease characterized by low bone mineral density anddeteriorated bone microstructure. This thesis aimed to determine whether corticalporosity is associated with previous fracture and increase the knowledge regarding theregulation of this bone trait.Methods: The studies included in this thesis were based on two well-defined cohorts.The first was a sub-sample from the Swedish part of the Osteoporotic fractures in men(MrOS) study. This cohort comprised of 456 older men (mean age 80.2 years). Thesecond cohort was the Sahlgrenska University hospital Prospective Evaluation of Riskof Bone fractures SUPERB study, which is based on 3030 elderly women (75-80years). Two sub-populations were used selected either on an X-ray verified hipfracture or available measurements of bone material properties. Bone mineral densitywas assessed with dual-energy X-ray absorptiometry. Bone geometry andmicrostructure were measured at the tibia with high-resolution peripheral quantitativecomputed tomography. Microindentation was performed with the hand-heldOsteoprobe to assess bone material strength.Results: Cortical porosity was associated with prevalent fracture in older men andprevalent hip fracture in older women independently of areal bone mineral density andclinical risk factors. Serum levels of 25-hydroxyvitamin D were inversely associatedwith cortical porosity independently of parathyroid hormone, indicating that vitamin Dmight directly regulate this bone trait. A high amount of adipose tissue was associatedwith higher cortical porosity and lower bone material strength. Conclusions: Cortical porosity is higher in individuals with a prevalent fracture, low vitamin D levels, or large amount of adipose tissue. These results indicate that corticalporosity is important for bone strength and has a role in the etiology of bone fractures.