Studies of bone microarchitecture in bone health in young and older adults and osteoarthritis
Creators: name: Ma, C
Publisher: name: University Of Tasmania
Year: 2024

description: Osteoporosis and osteoarthritis (OA) are the two major musculoskeletal conditions. Assessing bone mass and strength has been considered critical particularly for osteoporosis in understanding fracture risk and disease pathogenesis. Areal bone mineral density (aBMD) as a surrogate determinant of bone strength has long been used to assess fracture risk. Advanced high-resolution peripheral computed tomography (HRpQCT) can provide more accurate measurement of bone mass and strength in vivo. However, evidence of the utility of bone microarchitecture in discriminating fracture, assessing age-related bone loss, correlating to long-term exposures, such as body composition, dietary patterns, physical activity, and bone microarchitecture changes with OA are very limited in vivo. Given these important evidence gaps, this thesis aimed to describe the role of bone microarchitecture in osteoporosis and OA.We performed studies using samples from two population-based studies, the Tasmanian Older Adult Cohort (TasOAC) study and the Tasmanian birth cohort (T-bone) study. The TasOAC study is a prospective, population-based cohort study, for which adults aged between 50 and 79 years in 2002 were selected from the electoral roll in Southern Tasmania. T-bone is a Tasmanian birth cohort study, for which a total of 1500 infants at higher risk of sudden infant death syndrome (SIDS) from 1988 and 1989 were enrolled in southern Tasmania. Bone outcomes were aBMD at hip, spine, total body by dual-energy X-ray absorptiometry (DXA), cortical and trabecular bone microarchitecture at distal radius and tibia by HRpQCT. Exposures including body composition, vertebral deformity (VD) quantification were measured by DXA. Physical activity was measured by steps per day over seven consecutive days using a pedometer. Grip strength was measured by dynamometer. Serum 25-hydroxyvitamin D [25(OH)D] was assessed by radioimmunoassay. Physical fitness was estimated by physical working capacity at 170 beats/min (PWC170) using a Monark bicycle ergometer. Osteophyte scores and joint space narrowing were assessed by X-ray. Sports participation, dietary pattern, and anthropometrics were assessed during interview and collected by self-administered questionnaire.The first cross-sectional study examined discriminative utility of radial bone microarchitecture alone and in combinations with spine aBMD in VD. Compact cortical area, cortical thickness and compact cortical thickness alone had the largest area under the curve for discriminating VD. However, adding spine aBMD or radial volumetric bone mineral density (vBMD) to each cortical measure did not improve VD discrimination.The second cross-sectional study described differences in spine, total hip, and femoral neck aBMD, vBMD, cortical and trabecular bone microarchitecture at the distal radius between age of peak bone mass (PBM) and older adults. Compared to young adults, older adults had thinner compact-appearing cortices with larger and thicker transitional zone bone. Cortical porosity was modestly higher in older adults than in young adults. The magnitude of the difference in hip aBMD between older and young adults was slightly lower than of total radial vBMD.The third study described longitudinal associations of body composition, physical fitness, and sports participation from childhood to early adulthood with bone measures in early adulthood. Higher and increased lean mass during growth had beneficial association with spine, hip, and total body aBMD and radial and tibial bone microarchitecture in early adulthood, with the exception of vBMD. Fat mass in childhood had beneficial associations with vBMD and trabecular number, detrimental associations with bone geometry in early adulthood. However, continually increased fat mass during adolescence and early adulthood were detrimentally associated with aBMD and bone geometry in early adulthood. Commencing and persistent sports participation and higher physical fitness had beneficial associations with bone strength in early adulthood.In the fourth study, longitudinal data analysis was used to describe the associations between long-term modifiable factors with bone measures in older adults. Greater average lean mass over 5 years was beneficial for hip, spine, and total body aBMD and radial bone area and trabecular bone microarchitecture. Greater average fat mass over 5 years was detrimental for radial vBMD, bone area, and bone porosity. Notably, western dietary pattern scores were detrimentally associated with radial total, cortical, compact cortical, and outer transitional zone vBMD, and cortical, compact cortical, and outer transitional zone porosity. Steps per day was beneficially associated with inner transitional zone area and thickness, but no other measures.The final cross-sectional study described the association between radiographic hand OA (HOA) and HRpQCT measures. There was a decrease in trabecular number and bone volume fraction with increasing osteophyte scores and joint space narrowing (JSN) scores as well as an increase in trabecular separation and inhomogeneity at hand joints. In contrast, osteophyte scores and JSN scores in the hand were not associated with HRpQCT measures at the distal radius.In conclusion, this series of related studies using HRpQCT provide insights into osteoporosis, prevention of fracture, and OA. Assessing HRpQCT alone might be more beneficial for discriminating VD than DXA measures, as radial cortical measures had the best utility for discriminating VD when used alone. Bone microarchitecture had substantial differences between older adults and young adults at age of PBM. Long-term influence of modifiable factors on bone microarchitecture in young and older adults could be considered as potential strategies to improve and maintain bone mass and strength. Furthermore, subchondral bone microarchitecture changes in progression of HOA suggests bone size and trabecular disorganization increase with both osteophyte formation and JSN (proximal more than distal), while local bone density actually decreases.