Dual-energy X-ray Absorptiometry Does Not Represent Bone Structure in Patients with Osteoporosis

Abstract

Study Design Prospective cross-sectional exploratory study. Objective To evaluate the correlation between in vivo lumbar dual-energy x-ray absorptiometry (DXA) and parameters of bone architecture in micro–computed tomography (micro-CT) in patients with osteoporosis. Summary of Background Data DXA is the current diagnostic standard for evaluating osteoporosis. However, there are various concerns regarding its validity, especially in the spine. No study has so far investigated whether in vivo DXA correlates with the actual lumbar bone architecture. Methods Lumbar DXA scans were compared with micro-CT analysis of vertebral biopsies in patients with osteoporotic vertebral fractures (fracture group) and those without (control group). Preoperatively, all patients underwent a DXA scan (L1-L4). Intraoperative biopsies from nonfractured vertebrae (preferably L3) were analyzed by micro-CT regarding bone quantity and quality. The groups were compared regarding differences in DXA and micro-CT results. In each group, a correlation analysis was performed between DXA and micro-CT. Results The study included 66 patients (33 per group). Preoperative DXA results were worse in the fracture group than the control group (areal bone mineral density [aBMD] 0.95 vs. 1.31, T-score −1.97 vs. 0.92, each P < 0.001). Micro-CT analysis confirmed differences regarding quantitative parameters (bone/total volume: 0.09 vs. 0.12, P < 0.001) and qualitative parameters (connectivity index: 15.73 vs. 26.67, P < 0.001; structure model index: 2.66 vs. 2.27, P < 0.001; trabecular number: 2.11 vs. 2.28, P = 0.014) of bone architecture between both groups. The DXA results did not correlate with micro-CT parameters in the fracture group. In the control group, correlations were found for some parameters (bone/total volume vs. aBMD: r = 0.51, P = 0.005; trabecular number vs. aBMD: r = 0.56, P = 0.001). Conclusion These data constitute the first comparison of DXA measurements with microstructural analysis of vertebral biopsies in patients with osteoporosis. Our results indicate that lumbar DXA neither qualitatively nor quantitatively represents microstructural bone architecture and is therefore not a reliable tool for the evaluation of bone quality in the spine. Level of Evidence: 3

Fatty infiltration of the multifidus muscle independently increases osteoporotic vertebral compression fracture risk

“…However, it should be considered that the T-score sometimes shows discordance with osteoporotic fracture risk. Degenerated lumbar spine showed uncertainty for BMD measurement for aging [ 42 ]. Measurement of bone density can be affected by calcifying structures around the spine, which are the anterior and posterior longitudinal ligaments, ligament flavum, aorta, and interspinous ligament [ 43 , 44 ].…”

“…Degenerated lumbar spine showed uncertainty for BMD measurement for aging [ 42 ]. Measurement of bone density can be affected by calcifying structures around the spine, which are the anterior and posterior longitudinal ligaments, ligament flavum, aorta, and interspinous ligament [ 43 , 44 ]. Therefore, the prediction of fracture risk through only BMD is a challenge concerning the degenerative spine, especially in those who cannot use hip BMD due to history of hip fracture or surgery, and attempts are being made to compensate for this problem with a new method called the trabecular bone score to measure the microstructure of bones [ 45 ].…”

The association between paraspinal muscle parameters and vertebral pedicle microstructure in patients undergoing lumbar fusion surgery

“…Other parameters like bone microarchitecture and bone composition cannot be predicted with the current gold standard for evaluating BMD and DEXA [ 17 ]. Pumberger et al demonstrated that DEXA measurements of the spine do not properly represent the microstructure of the vertebral body and are therefore not a reliable tool to determine bone quality in the spine [ 24 ].…”

Osteosarcopenia in the Spine Beyond Bone Mineral Density

“…However, areal bone mineral density, quantifies primarily the quantity of bone and does not capture the other factors that contribute to bone integrity, such as microarchitecture, bone remodeling, and collagen properties. [15][16][17] Bone collagen is subject to posttranslational modifications, such as non-enzymatic collagen cross-linking, resulting in advanced glycation endproducts (AGEs). 17 The accumulation of AGEs is associated with impaired mechanical bone properties indicative of poor bone quality.…”

“…Osteoporosis is commonly diagnosed using dual-energy x-ray absorptiometry derived from areal bone mineral density. However, areal bone mineral density, quantifies primarily the quantity of bone and does not capture the other factors that contribute to bone integrity, such as microarchitecture, bone remodeling, and collagen properties 15–17 . Bone collagen is subject to posttranslational modifications, such as non-enzymatic collagen cross-linking, resulting in advanced glycation endproducts (AGEs) 17 .…”