Association of Regional Bone Synthetic Activities of Vertebral Corners and Vertebral Bodies Quantified Using 18F-Fluoride Positron Emission Tomography with Bone Mineral Density on Dual Energy X-ray Absorptiometry in Patients with Ankylosing Spondylitis.

Seung-Geun Lee,Kyoungjune Pak,In-Joo Kim,Keunyoung Kim,Seong-Jang Kim,Aran Kim,Dong Hyun Sohn

doi:10.3390/jcm9082656

Abstract

We investigated whether the bone-synthetic activities of vertebral bodies or vertebral corners quantified using 18F-fluoride positron emission tomography (PET) was associated with bone mineral density (BMD) at the corresponding lumbar vertebrae in ankylosing spondylitis (AS) at each vertebra level. We analyzed 48 lumbar vertebrae in 12 AS patients who underwent 18F-fluoride PET and dual energy X-ray absorptiometry (DXA). The mean standardized uptake values (SUVmean) of the vertebral body and corners from L1 to L4 were measured using the spatially separated region of interest (ROI). The L1–L4 BMDs were calculated based on the DXA (“conventional BMD”). The BMD of the internal vertebral bodies was measured by manually drawing ROIs to represent the trabecular BMD (“alternative BMD”). After adjusting the within-patient correlation, the 18F-fluoride SUVmean of the vertebral corners but not that of vertebral bodies was significantly related with the conventional BMD of the vertebra. Otherwise, the 18F-fluoride uptake of both the vertebral and vertebral bodies was significantly related with the alternative BMD. The bone-synthetic activities of the vertebral corners may be more closely related with BMD than those of the vertebral bodies, suggesting that the effects of regional bone metabolism at the vertebral corners and bodies on BMD differ in AS.

Highlights

Ankylosing spondylitis (AS) is a chronic rheumatic disease characterized by inflammation in the axial skeleton such as the sacroiliac joints and spine, subsequently leading to new bone formation
The 18F-fluoride SUVmean of the vertebral bodies was significantly related with the alternative bone mineral density (BMD) but not with the conventional BMD
The exact reasons for our finding are not fully understood, one possible explanation is that the effect of regional bone metabolism in vertebral corners on lumbar spine BMD measured by dual energy X-ray absorptiometry (DXA) may be large enough to offset the statistically significant correlation between the 18F-fluoride uptake of vertebral bodies and conventional BMD

Summary

Introduction

Ankylosing spondylitis (AS) is a chronic rheumatic disease characterized by inflammation in the axial skeleton such as the sacroiliac joints and spine, subsequently leading to new bone formation. In AS, there is an apparent paradox of excessive bone formation and bone loss at anatomical sites closely located to each other; the regional bone metabolism between the vertebral corners (cortical bone) and bodies (trabecular bone) may differ in relation to the bone mineral density (BMD) of the vertebrae. To identify this issue, quantitative assessment of bone metabolism in specific sites of the vertebrae may be necessary

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Conclusion