Relationship between spinal structural damage on radiography and bone fragility on CT in ankylosing spondylitis patients

The prevalence of vertebral fractures in diffuse idiopathic skeletal hyperostosis and ankylosing spondylitis: A systematic review and meta-analysis

Background

Subjects with ankylosing spinal disorders, including diffuse idiopathic skeletal hyperostosis (DISH) and ankylosing spondylitis (AS) are more prone to vertebral fractures and frequently present with neurological deficit compared to the patients without an ankylosed spine. Moreover, prevalent vertebral fractures are an important predictor for subsequent fracture risk. However, the pooled fracture prevalence for DISH is unknown and less recent for AS. We aimed to systematically investigate the prevalence and risk of vertebral fractures in DISH and AS populations.

Methods

Publications in Medline and EMBASE were searched from January 1980 until July 2023 for cohort studies reporting vertebral fractures in AS and DISH. Data on prevalence were pooled with random effects modeling after double arcsine transformation. Heterogeneity was assessed with I2 statistics and we performed subgroup analysis and meta-regression to explore sources of heterogeneity.

Results

We included 7 studies on DISH (n = 1,193, total fractures = 231) with a pooled vertebral fracture prevalence of 22.6% (95%CI: 13.4%-33.4%). For AS, 26 studies were included (n = 2,875, total fractures = 460) with a pooled vertebral fracture prevalence of 15.2% (95%CI: 11.6%-19.1%). In general, fracture prevalence for AS remained similar for several study-level and clinically relevant characteristics, including study design, diagnostic criteria, spine level, and patient characteristics in subgroup analysis. AS publications from 2010 to 2020 showed higher fracture prevalence compared to 1990 to 2010 (18.6% vs. 11.6%). Fractures in DISH were most common at the thoracolumbar junction, whereas for AS, the most common location was the mid-thoracic spine.

Conclusions

Vertebral fractures are prevalent in AS and DISH populations. Differences in fracture distribution along the spinal axis exist between the 2 disorders. Additional longitudinal studies are needed for incident fracture assessment in patients with ankylosing spinal disorders.

Probability of the 10-year Risk of Hip and Major Osteoporotic Fracture in Non-radiographic Axial Spondyloarthritis

BACKGROUND

Fracture risk in non-radiographic spondyloarthritis is underestimated. A reliable tool such as the Fracture Risk Assessment tool (FRAX) may assess this risk probability. This study aimed to assess the fracture risk by the FRAX score in patients with nr-axSpA and to determine factors associated with high fracture risk.

METHODS

We conducted a retrospective study of nr-axSpA patients meeting the Assessment of SpondyloArthritis International Society (ASAS) classification criteria for spondyloarthritis. All patients had Bone Mineral Density (BMD) by dual-energy X-ray absorptiometry (DEXA). The 10- year probability of major osteoporotic fracture (MOF) and hip fracture (HF) was calculated using the Fracture Risk Assessment Tool (FRAX).

RESULTS

Among 40 patients with nr-axSpA, 27 were women (67.5%). Their mean age was 43.7 ± 12.1 years. The mean disease duration was 3.15 ± 2.7 years. Eighteen patients (45%) had osteopenia, and 12 patients (30%) had osteoporosis. The median HF FRAX was 0% [0-1.2]. The median MOF FRAX was 0.5% [0.3-1.8]. MOF FRAX was positively correlated with age (p = 0.002), disease onset age (p = 0.006), disease duration (p = 0.024), and the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) (p < 0.0001), and negatively correlated with daily calcium intake (p < 0.0001). HF FRAX was positively correlated with mSASSS (p < 0.0001) and negatively correlated with daily calcium intake (p = 0.005).

CONCLUSION

Our study confirmed the frequency of bone loss during nr-axSpA and showed that osteoporotic risk fracture was related not only to traditional risk factors for osteoporosis but also to disease-related factors.

Inflammation, bone loss and 2-year bone formation at the same vertebra in axial spondyloarthritis: a multilevel MRI and low-dose CT analysis

OBJECTIVE

To investigate whether in radiographic axial spondyloarthritis (r-axSpA) inflammation is associated with lower trabecular bone density (TBD), and subsequently, if a lower TBD increases the likelihood of 2-year bone formation at the same vertebra.

METHODS

Whole spine (C3-L5) data from patients included in the multicentre 2-year Sensitive Imaging in Ankylosing Spondylitis cohort was used. Two readers measured baseline TBD by Hounsfield units (HU) on low-dose CT (ldCT). Baseline MRI bone marrow oedema (BME) status scores and ldCT syndesmophyte formation and/or growth change-from-baseline scores were assessed by three and two readers, respectively. Average of readers' continuous measurements or readers' agreement in binary scores generated within the same vertebra (1-present in ≥1 quadrant/0-absent in all quadrants) were used. Multilevel generalised estimating equations models were used, the unit of analysis being the vertebra.

RESULTS

In 50 patients with r-axSpA, TBD HU decreased from cranial to caudal vertebrae. Baseline MRI-BME was present in 300/985 (30%) and syndesmophytes in 588/910 (65%) vertebrae, both most prevalent at thoracolumbar region. Syndesmophyte formation or growth was observed in 18% of at-risk vertebrae (124/691). A significant confounder-adjusted association was found between inflammation and lower TBD (regression coefficient=-51; 95% CI-63 to -39). TBD was not associated with 2-year syndesmophyte formation or growth (adjusted OR 1.00; 95% CI 0.99 to 1.00).

CONCLUSION

In r-axSpA, while vertebral inflammation was associated with lower vertebral TBD, lower vertebral TBD itself did not increase the risk for new bone formation at the same vertebra. In preventing syndesmophyte progression, targeting local inflammation seems more important than targeting vertebral trabecular bone loss.

Hounsfield Units measured in low dose CT reliably assess vertebral trabecular bone density changes over two years in axial spondyloarthritis

OBJECTIVES

To describe low dose Computed Tomography (ldCT) Hounsfield Units (HU) two-year change-from-baseline values (expressing trabecular bone density changes) and analyse their inter-reader reliability per vertebra in radiographic axial spondyloarthritis (r-axSpA).

METHODS

We used 49 patients with r-axSpA from the multicentre two-year Sensitive Imaging in Ankylosing Spondylitis (SIAS) study. LdCT HU were independently measured by two trained readers at baseline and two years. Mean (standard deviation, SD) for the change-from-baseline HU values were provided per vertebra by reader. Intraclass correlation coefficients (ICC; absolute agreement, two-way random effect), Bland-Altman plots and smallest detectable change (SDC) were obtained. Percentages of vertebrae in which readers agreed on the direction of change and on change >|SDC| were computed.

RESULTS

Overall, 1,053 (98% of all possible) vertebrae were assessed by each reader both at baseline and two years. Over two years, HU mean change values varied from -23 to 28 and 29 for reader 1 and 2, respectively. Inter-reader reliability of the two-year change-from-baseline values per vertebra was excellent: ICC:0.91-0.99; SDC:6-10; Bland-Altman plots were homoscedastic, with negligible systematic error between readers. Readers agreed on the direction of change in 88-96% and on change >|SDC| in 58-94% of vertebrae, per vertebral level, from C3 to L5. Overall, similar results were obtained across all vertebrae.

CONCLUSION

LdCT measurement of HU is a reliable method to assess two-year changes in trabecular bone density at each vertebra from C3-L5. Being reliable across all vertebrae, this methodology can aid the study of trabecular bone density changes over time in r-axSpA, a disease affecting the whole spine.

Low-dose CT hounsfield units: a reliable methodology for assessing vertebral bone density in radiographic axial spondyloarthritis

Objective

Studying vertebral bone loss in radiographic axial spondyloarthritis (r-axSpA) has been challenging due to ectopic bone formation. We cross-sectionally analysed low-dose CT (ldCT) trabecular bone density Hounsfield units (HU) measurements and calculated inter-reader reliability at the vertebral level in patients with r-axSpA.

Methods

LdCT scans of 50 patients with r-axSpA from the sensitive imaging in ankylosing spondylitis study, a multicentre 2-year prospective cohort were included. Trabecular bone HU taken from a region of interest at the centre of each vertebra (C3-L5) were independently assessed by two trained readers. HU mean (SD), and range were provided at the vertebral level, for each reader and centre separately. Inter-reader reliability and agreement were assessed using intraclass correlation coefficients (ICC; single measurements, absolute agreement, two-way mixed effects models); smallest detectable difference and Bland-Altman plots.

Results

Overall, 1100 vertebrae were assessed by each reader. HU values decreased from cranial to caudal vertebrae. For readers 1 and 2 respectively, the highest mean (SD) HU value was obtained at C3 (354(106) and 355(108)), and the lowest at L3 (153(65) and 150 (65)). Inter-reader reliability was excellent (ICC(2,1):0.89 to 1.00). SDD varied from 4 to 8. For most vertebrae, reader 1 scored somewhat higher than reader 2 (mean difference of scores ranging from −0.6 to 2.9 HU). Bland-Altman plots showed homoscedasticity.

Conclusion

LdCT measurement of HU is a feasible method to assess vertebral bone density in r-axSpA with excellent inter-reader reliability from C3 to L5. These results warrant further validation and longitudinal assessment of reliability.

Subchondral bone attenuation coefficient utility of the sacroiliac margins to differentiate spondyloarthritis and osteitis condensans ilii

Introduction

Differentiating ankylosing spondylitis (AS) from osteitis condensans ilii (OCI) remains challenging for clinicians. The aim of this study was to determine whether Subchondral Bone Attenuation Coefficient of the SacroIliac margins (SBAC-SI) is different in AS, OCI and diffuse idiopathic skeletal hyperostosis (DISH).

Methods

A monocentric retrospective observational study was performed at the University Hospital of Besançon. Patients included were followed for AS, DISH or OCI and underwent CT scan including sacroiliac joint. Patients with tumour lesion of bone or a history of pelvic radiotherapy were excluded. AS and OCI patients were matched with a control of the same age and sex. SBAC-SI was evaluated by the sum of 24 identical circular regions of interest, 8 per slice (anterior, middle and posterior).

Results

Thirty AS and AS controls, 31 DISH, 29 OCI and OCI controls were included. SBAC-SI score was 9727 (±2430) in the OCI group (p<0.001), 3563 (±1860) in the AS group, 3899 (±1937) in the DISH group, 4224 (±1693) in the AS control group and 5445 (±1205) in the OCI control group. A threshold of 7500 HU had the best discriminative value between OCI and AS (youden index: 0.89). In AS, disease duration is negatively associated with SBAC-SI (r: −0.623; p<0.01) and HLA B27 is associated with lower SBAC-SI (6523 (5198; 7137) vs 2809 (1568; 3371); p<0.001).

Conclusion

SBAC-SI is significatively different between AS and OCI and could help to distinguish these two diseases.

Prevalence and Factors of Osteoporosis and High Risk of Osteoporotic Fracture in Patients with Ankylosing Spondylitis: A Multicenter Comparative Study of Bone Mineral Density and the Fracture Risk Assessment Tool

Background: We investigated the prevalence of and the factors associated with a high risk of osteoporotic fractures in Korean patients with ankylosing spondylitis (AS). Methods: This was a multicenter, retrospective study including 219 AS patients from five university hospitals; the control group was selected by matching age and sex with those of the AS patients. The fracture risk was evaluated based on bone mineral density (BMD) measured by dual-energy X-ray absorptiometry and the fracture risk assessment tool (FRAX) with/without BMD. Results: The mean age of the patients was 47.6 years, and 144 (65.8%) patients were men. According to the WHO criteria and FRAX with/without BMD, the candidates for pharmacological treatment were 44 (20.1%), 20 (13.2%), and 23 (15.1%) patients, respectively, significantly more than those in the healthy control group. Among them, the proportion of patients receiving osteoporosis treatment was 39.1–75%. In logistic regression analysis, menopause was an independent factor for the high risk of fracture according to the WHO criteria and FRAX with/without BMD. C-reactive protein level (odds ratio (OR) 3.8 and OR 6) and glucocorticoid use (OR 1.5 and OR 1.7) were associated with a high risk of osteoporotic fracture based on FRAX without BMD and osteoporosis diagnosed according to the WHO criteria. Conclusions: Our study suggests that both FRAX and WHO criteria may be complementary for treatment decisions to reduce osteoporotic fractures in patients with AS.