Trabecular bone score value is associated with new bone formation independently of fat metaplasia on spinal magnetic resonance imaging in patients with ankylosing spondylitis

Bibliometric analysis of publications on trabecular bone score (TBS)

Purpose

Trabecular bone score (TBS), as a texture indicator of bone microarchitecture, predicts the risk of fracture. This study aims to explore the knowledge map of TBS.

Methods

We searched Scopus for "trabecular bone score" or "trabecular score" from the beginning to 2021. Our inclusion criteria were original articles and reviews that were related to TBS and our exclusion criteria were non-English articles, non-related to TBS, and document type other than original articles and reviews. and related documents were included for bibliometric analysis. Excel, VOS viewer, and Science of Science (Sci2) software were used for data synthesis.

Results

From 749 retrieved articles, 652 articles were included for analysis. These documents were cited 12,153 times and had an H-index of 56. The most productivity belonged to the USA (n = 130 documents), Switzerland (n = 101), and Italy (n = 67). "Osteoporosis International" (n = 80) had the highest participation in publishing. The research topics of interest were mainly related to the applicability of TBS for fracture risk assessment in chronic endocrine disorders such as osteoporosis and diabetes mellitus. Bursting analysis of the title and abstract revealed the initial focus of the discriminative power of TBS for osteoporotic fracture and the more recent focus on comparing bone mineral density (BMD) and TBS in a variety of chronic diseases.

Conclusion

The number of annual publications on TBS has increased, especially after 2016. These publications highlight the importance of in-depth knowledge of TBS in predicting fracture risk and also its strengths and limitations of treatment monitoring in different health conditions.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01338-7.

Prevalence of low trabecular bone score and its association with disease severity and activity in patients with axial spondyloarthritis

Axial spondyloarthritis (axSpA) increases the risk of osteoporosis and vertebral fractures. Bone mineral density (BMD) measured by dual X-ray absorptiometry (DXA) has limitations in axSpA patients. Trabecular bone score (TBS) indirectly assesses bone microarchitecture and can be used to predict fracture risk. However, few studies have investigated the role of TBS in axSpA patients. The objective of this study were to compare TBS between axSpA patients and 1:1 sex- and age-matched healthy volunteers and determine factors associated with low TBS in axSpA patients. A cross-sectional study was conducted in two tertiary-care hospitals. A total of 137 axSpA patients and healthy volunteers were enrolled. Demographics, disease characteristics, and risk factors for osteoporosis were recorded. TBS, BMD at the lumbar spine, hip, and vertebral fractures were assessed by DXA. Low TBS was defined as a TBS value < 1.230. Factors associated with low TBS were examined by logistic regression. Most patients were male (75.9%) and tested positive for HLA-B27 (88.3%). The mean (SD) age was 42.8 (12.0) years. The mean (SD) of TBS in the axSpA patients was lower than those in the healthy volunteers [1.402 (0.107) vs 1.440 (0.086), respectively; p = 0.002]. The mean (SD) of lumbar BMD in the axSpA patients was higher than in healthy volunteers [1.186 (0.212) vs 1.087 (0.124), p < 0.001], whereas the mean (SD) of femoral neck BMD in the axSpA group was lower than that in the healthy volunteers [0.867 (0.136) vs 0.904 (0.155), p = 0.038]. Disease severity as indicated by sacroiliac joint fusion and a high ASDAS score were associated with low TBS with the odds ratios (95% confidence interval) of 11.8 (1.2-115.4) and 5.2 (1.6-16.9), respectively. In conclusion, axSpA patients had a higher prevalence of low TBS than healthy volunteers. Sacroiliac joint fusion and a high ASDAS score were associated with low TBS.

Syndesmophyte Growth in Ankylosing Spondylitis: from Laboratory to Bedside

PURPOSE OF REVIEW

This study aims to review recent studies on risk factors for syndesmophyte growth in ankylosing spondylitis (AS) and on treatment effects.

RECENT FINDINGS

New genetic studies, including a genome-wide association study, provided only limited evidence of specific genetic associations with radiographic severity. Measures of inflammation, including vertebral osteitis and C-reactive protein level, were strongly associated with radiographic progression, while studies of adipokines had mixed results. Mesenchymal stem cells from HLA-B27 positive AS patients were found to promote vertebral ossification via a pathway of B27 misfolding, retinoic acid receptor-β activation, and increased bone alkaline phosphatase. Low vertebral trabecular bone density is associated with syndesmophyte growth, with reciprocal effects when bridged. Several observational studies suggested radiographic severity was reduced by treatment with tumor necrosis factor inhibitors, particularly when longer than 2 years. Syndesmophyte development in AS is the result of a complex, incompletely understood, interplay of inflammatory and mechanical factors.

Dickkopf-1 directs periosteal bone formation in two murine models of inflammatory arthritis

OBJECTIVE

The Wnt signalling antagonist Dickkopf-1 (DKK1) inhibits osteoblast differentiation and function and has been described to play a central role in promoting bone loss, while blockade of DKK1 increases bone formation. We investigated the effects of DKK1 on periosteal new bone formation in two murine models of inflammatory arthritis, the antigen-induced arthritis (AIA) and K/BxN serum transfer arthritis (STA) models.

METHOD

The flare variant of AIA was induced in wild-type mice and a blocking antibody to DKK1, control rat immunoglobulin G (IgG), or phosphate-buffered saline (PBS) was administered starting on day 14, a time at which inflammation and erosions are known to be established. Knees were assessed for histological inflammation and periosteal new bone formation was quantitated. In addition, STA was generated in transgenic (Tg) mice with osteoblast-specific overexpression of Dkk1 and littermate controls. New bone formation around the wrists of these mice was quantified by micro-computed tomography.

RESULTS

Blockade of DKK1 in arthritic mice resulted in significantly more periosteal new bone formation compared to mice treated with control rat IgG or PBS. Conversely, in the setting of increased Dkk1 expression, arthritic Dkk1 Tg mice developed significantly less periosteal new bone than arthritic controls.

CONCLUSION

DKK1 is a regulator of periosteal bone formation in inflammatory arthritis. Thus, regulation of DKK1 may be considered as a therapeutic approach in inflammatory diseases in which patients suffer from excessive periosteal bone formation, such as spondyloarthritis.

Chemical Shift-Encoded MRI of Bone Metabolic Markers in Ankylosing Spondylitis

Objective

To investigate the feasibility and correlation of sacroiliac joint (SIJ) fat fraction (FF) and R2^∗ as markers of bone metabolism in patients with ankylosing spondylitis (AS).

Methods

75 AS patients were classified into an early active group (EA), late active group (LA), and inactive group (IA). Additionally, 54 matched healthy individuals were selected to be part of the normal control group (NC). All participants underwent chemical shift encoded based MRI (IDEAL-IQ) and routine clinical SIJ MRI at 3.0 T. FF and R2^∗ were measured in subchondral bone, bone marrow edema (BME), and fat metaplasia (FM). Out of the participants, 39 with BME lesions (15 from EA, 16 from LA, 8 from IA) and 39 with FM lesions (9 from EA, 17 from LA, 13 from IA) were included. Differences in FF, R2^∗ value for subchondral bone of all participants and for BME, FM lesions were evaluated. Subsequently, different stages of BME and FM in patient groups were compared, and the relationship between FF and R2^∗ was analyzed.

Results

A significant difference in FF was demonstrated among the BME, FM and the normal bone marrow (p < 0.001), meanwhile, the difference of R2^∗ value in FM was significantly lower (p = 0.034, 0.012) than that of BME and that of normal bone marrow. At lever of different lesions, only the FF for BME was significantly different among 3 patient groups (p = 0.001), while there was no significantly different FF for FM among 3 patient groups. Unlike in BME lesions, the FF in FM lesions had a negative correlation with R2^∗ (p < 0.001, r = −0.488).

Conclusion

FF and R2^∗ measurements help to quantitatively analyze the bone marrow fat composition and bony trabecular microstructure changes in AS, providing a noninvasive and accurate assessment basis for AS bone metabolism abnormalities.

Trabecular Bone Score in Rheumatic Disease

PURPOSE OF REVIEW

Patients with rheumatic disease are at high risk of low bone mass and osteoporotic fracture. Trabecular bone score (TBS), derived from lumbar spine dual-energy x-ray absorptiometry (DXA), is a novel measure of bone texture that independently predicts fracture risk. This review examines the role of TBS in rheumatic disease including fracture prediction.

RECENT FINDINGS

Most studies concerning TBS and rheumatic disease are cross-sectional, with consistent evidence of lower TBS in patients with rheumatic disease compared to controls. Recent studies have shown association and predictive ability of TBS for prevalent fracture, and the few longitudinal studies showed predictive ability of TBS for incident fracture. TBS in ankylosing spondylitis is of interest given the high rates of vertebral fracture and technical difficulty with lumbar spine bone mineral density. TBS degradation has been associated with disease activity in ankylosing spondylitis, systemic sclerosis, and rheumatoid arthritis. Glucocorticoid exposure is associated with lower TBS, and predicts prevalent fracture, in patients with rheumatic conditions.

Trabecular Bone Score (TBS) in Patients with Early Ankylosing Spondylitis-Limited Utility

Purpose: Ankylosing spondylitis (AS) not only results in pathological ossification of the spine, but can also be associated with osteoporosis. Due to the presence of syndesmophytes and possible involvement of the hip joints, classical dual X-ray absorptiometry (DXA) is of limited use in patients with advanced stages of AS. Trabecular bone score (TBS) is a method complementary to DXA, providing additional information about bone microarchitecture. There is a growing body of evidence for the usefulness of TBS in AS patients. The aim of this study was to assess the clinical utility of TBS in patients with AS. Methods: Patients with AS underwent DXA with additional TBS assessment. A cross-sectional analysis of the frequency of osteoporosis and bone microarchitecture deterioration and their association with patients’ characteristics was done. Results: A total of 51 male patients, mean age 40.7 years, were enrolled. Osteoporosis was diagnosed in seven patients (13.7%). Lumbar bone mineral density (BMD) was higher (p < 0.001) than femoral BMD, indicating abnormal BMD readings in the spine caused by syndesmophytes. Patients with DXA-diagnosed osteoporosis had lower TBS (p = 0.03) and TBS T-score (p = 0.043) values compared to patients without osteoporosis. However, disturbed bone microarchitecture (TBS < 1.23) was present in only three patients (5.9%). None of the patients had a history of an osteoporotic fracture. A lower TBS T-score (p = 0.032) was demonstrated in patients with sacroiliitis grade 4 than in patients with sacroiliitis grade 2, with no significant differences in BMD and T-score values. Conclusion: Among patients with early AS, the clinical utility of TBS is limited—it does not add value to DXA.

Trabecular bone loss contributes to radiographic spinal progression in patients with axial spondyloarthritis

OBJECTIVES

To investigate the longitudinal relationship between trabecular bone loss and spinal progression in axial spondyloarthritis (axSpA).

METHODS

Patients enrolled in the Incheon Saint Mary's axSpA prospective observational cohort were evaluated. The number of syndesmophytes was assessed by two trained readers at baseline and at 2 and 4 years follow-up. Trabecular bone loss was assessed using the trabecular bone score (TBS). Disease activity measures included the BASDAI, ASDAS, CRP, and ESR. The relationship between trabecular bone loss and radiographic damage was investigated using generalized estimating equation models with 2 year time lags.

RESULTS

Of the 245 patients included (80% males; mean (SD) age, 37 (12) years), 26 (11%) had mild trabecular bone loss (1.23-1.31) and 25 (10%) had severe trabecular bone loss (≤1.23) at baseline. Trabecular bone loss was associated with longitudinal radiographic spinal progression. Those with severe trabecular bone loss at baseline had an average 0.42 more syndesmophytes/2 years than those with normal TBS. Multivariate analysis revealed that severe trabecular bone loss compared with normal TBS resulted in an additional 0.4 syndesmophytes over 2 years. Adjusting for significant clinical factors revealed that both mild and severe trabecular bone loss were independent risk factors for new syndesmophyte formation over the next 2 years (OR [95% CI] = 2.4 [1.1-5.1]) and OR [95% CI] = 4.0 [1.6-9.7], respectively).

CONCLUSIONS

Trabecular bone loss is longitudinally associated with spinal progression of axSpA. The more severe the trabecular bone loss, the stronger the effect on the progression of the spine.