Combined Hind Limb Suspension and Srankle on Bone Strength in Mic by Finite Element Analysis: Effects of Anatomic Model Height

Abstract

With commercial space travel on the horizon, it is necessary to understand how the microgravity environment present in space impacts bone in conjunction with the osteoporotic effects of aging. The microgravity environment causes an absence of skeletal loading, which in turn increases resorption and decreases formation of bone. Since hind limb suspension (HLS) has been demonstrated as an effective simulator of the effects of microgravity on bone, it was used to simulate microgravity in this study. Additionally, the elderly population suffers from hormonally induced bone loss which is often a precursor to injuries such as hip fracture (often fatal in this population). Increased levels of Receptor Activator of Nuclear factor κ-β Ligand (RANKL) are often present in individuals with decreased estrogen levels, which is associated with decreases in bone strength post menopause. Previous work found that soluble RANKL (sRANKL) results in bone loss and a decrease in bone mineral density (BMD) similar to that experienced in postmenopausal osteoporotic women, and was thus used to simulate osteoporosis associated with aging in this study [2]. In this study, in vivo μCT model derived finite element analysis (FEA) quantitatively measures changes in bone FE volume, stiffness, structural efficiency, and the 10th and 90th percentile nodal Von Mises stresses as they vary with changes in anatomic model size. These parameters are associated with the microstructural mechanics of bone, and understanding how strength is decreased on a structural level may lead to the development of in vivo bone strength testing clinically, and in space.