IntroductionOsteoporosis can be a complication of ankylosing spondylitis (AS), but diagnosing spinal osteoporosis can be difficult since pathologic new bone formation interferes with the assessment of the bone mineral density (BMD). The aims of the current study were to investigate prevalence and risk factors for reduced BMD in a Swedish cohort of AS patients, and to examine how progressive ankylosis influences BMD with the use of dual-energy x-ray absorptiometry (DXA) of the lumbar spine in different projections.MethodsMethods of assessment were questionnaires, back mobility tests, blood samples, lateral spine radiographs for syndesmophyte grading (mSASSS), DXA of the hip, radius and lumbar spine in anteroposterior (AP) and lateral projections with estimation of volumetric BMD (vBMD).ResultsAS patients (modified New York criteria), 87 women and 117 men, mean age 50 ± 13 years and disease duration 15 ± 11 years were included. According to World Health Organization (WHO) criteria 21% osteoporosis and 44% osteopenia was diagnosed in patients > = 50 years. Under age 50 BMD below expected range for age was found in 5%. Interestingly lateral lumbar DXA showed significantly lower BMD and revealed significantly more cases with osteoporosis as compared with AP DXA. Lumbar vBMD was not different between sexes, but women had significantly more lumbar osteoporosis measured with AP DXA (P < 0.001). Men had significantly higher mSASSS (P < 0.001). Low BMD was associated with high age, disease duration, mSASSS, Bath Ankylosing Spondylitis Metrology Index (BASMI), inflammatory parameters and low body mass index (BMI). Increasing mSASSS correlated significantly with decreasing lateral and volumetric lumbar BMD, while AP lumbar BMD showed tendency to increase.ConclusionsOsteoporosis and osteopenia is common in AS and associated with high disease burden. Lateral and volumetric lumbar DXA are more sensitive than AP DXA in detecting osteoporosis and are less affected by syndesmophyte formation.

IntroductionOsteoporosis of the axial skeleton is a known complication of ankylosing spondylitis (AS), but bone loss affecting the peripheral skeleton is less studied. This study on volumetric bone mineral density (vBMD) and bone microarchitecture in AS was conducted to compare peripheral vBMD in AS patients with that in healthy controls, to study vBMD in axial compared with peripheral bone, and to explore the relation between vertebral fractures, spinal osteoproliferation, and peripheral bone microarchitecture and density.MethodsHigh-resolution peripheral quantitative computed tomography (HRpQCT) of ultradistal radius and tibia and QCT and dual-energy x-ray absorptiometry (DXA) of lumbar spine were performed in 69 male AS patients (NY criteria). Spinal radiographs were assessed for vertebral fractures and syndesmophyte formation (mSASSS). The HRpQCT measurements were compared with the measurements of healthy controls.ResultsThe AS patients had lower cortical vBMD in radius (P = 0.004) and lower trabecular vBMD in tibia (P = 0.033), than did the controls. Strong correlations were found between trabecular vBMD in lumbar spine, radius (rS = 0.762; P < 0.001), and tibia (rS = 0.712; P < 0.001).When compared with age-matched AS controls, patients with vertebral fractures had lower lumbar cortical vBMD (-22%; P = 0.019), lower cortical cross-sectional area in radius (-28.3%; P = 0.001) and tibia (-24.0%; P = 0.013), and thinner cortical bone in radius (-28.3%; P = 0.001) and tibia (-26.9%; P = 0.016).mSASSS correlated negatively with trabecular vBMD in lumbar spine (rS = -0.620; P < 0.001), radius (rS = -0.400; p = 0.001) and tibia (rS = -0.475; p < 0.001) and also with trabecular thickness in radius (rS = -0.528; P < 0.001) and tibia (rS = -0.488; P < 0.001).Adjusted for age, syndesmophytes were significantly associated with decreasing trabecular vBMD, but increasing cortical vBMD in lumbar spine, but not with increasing cortical thickness or density in peripheral bone. Estimated lumbar vBMD by DXA correlated with trabecular vBMD measured by QCT (rS = 0.636; P < 0.001).ConclusionsLumbar osteoporosis, syndesmophytes, and vertebral fractures were associated with both lower vBMD and deteriorated microarchitecture in peripheral bone. The results indicate that trabecular bone loss is general, whereas osteoproliferation is local in AS.

BackgroundKnowledge about predictors of new spinal bone formation in patients with ankylosing spondylitis (AS) is limited. AS-related spinal alterations are more common in men; however, knowledge of whether predictors differ between sexes is lacking. Our objectives were to study spinal radiographic progression in patients with AS and investigate predictors of progression overall and by sex.MethodsSwedish patients with AS, age (mean ± SD) 50 ± 13 years, were included in a longitudinal study. At baseline and at 5-year follow up, spinal radiographs were graded according to the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS). Predictors were assessed by questionnaires, spinal mobility tests and blood samples.ResultsOf 204 patients included, 166 (81%) were re-examined and 54% were men. Men had significantly higher mean mSASSS at baseline and higher mean increase in mSASSS than women (1.9 ± 2.8 vs. 1.2 ± 3.3; p = 0.005) More men than women developed new syndesmophytes (30% vs. 12%; p = 0.007). Multivariate logistic regression analyses with progression ≥ 2 mSASSS units over 5 years or development of new syndesmophytes as the dependent variable showed that presence of baseline AS-related spinal radiographic alterations and obesity (OR 3.78, 95% CI 1.3 to 11.2) were independent predictors of spinal radiographic progression in both sexes. High C-reactive protein (CRP) was a significant predictor in men, with only a trend seen in women. Smoking predicted progression in men whereas high Bath Ankylosing Spondylitis Metrology Index (BASMI) and exposure to bisphosphonates during follow up (OR 4.78, 95% CI 1.1 to 20.1) predicted progression in women.ConclusionThis first report on sex-specific predictors of spinal radiographic progression shows that predictors may partly differ between the sexes. New predictors identified were obesity in both sexes and exposure to bisphosphonates in women. Among previously known predictors, baseline AS-related spinal radiographic alterations predicted radiographic progression in both sexes, high CRP was a predictor in men (with a trend in women) and smoking was a predictor only in men.Trial registrationClinicalTrials.gov, NCT00858819. Registered on 9 March 2009. Last updated 28 May 2015.

VF in AS are common but are often not diagnosed. VF are associated with advanced age, longstanding disease, impaired back mobility, syndesmophyte formation, and lower BMD in both the central and peripheral skeleton. BMD in the femoral neck, total hip, and estimated vBMD showed the strongest association with VF.

Background and purpose Charcot neuropathy is characterized by bone destruction in a foot leading to deformity, instability, and risk of amputation. Little is known about the pathogenic mechanisms. We hypothesized that the bone-regulating Wnt/β-catenin and RANKL/OPG pathways have a role in Charcot arthropathy.Patients and methods 24 consecutive Charcot patients were treated by off-loading, and monitored for 2 years by repeated foot radiography, MRI, and circulating levels of sclerostin, dickkopf-1, Wnt inhibitory factor-1, Wnt ligand-1, OPG, and RANKL. 20 neuropathic diabetic controls and 20 healthy controls served as the reference.Results Levels of sclerostin, Dkk-1 and Wnt-1, but not of Wif-1, were significantly lower in Charcot patients than in the diabetic controls at inclusion. Dkk-1 and Wnt-1 levels responded to off-loading by increasing. Sclerostin levels were significantly higher in the diabetic controls than in the other groups whereas Wif-1 levels were significantly higher in the healthy controls than in the other groups. OPG and RANKL levels were significantly higher in the Charcot patients than in the other groups at inclusion, but decreased to the levels in healthy controls at 2 years. OPG/RANKL ratio was balanced in all groups at inclusion, and it remained balanced in Charcot patients on repeated measurement throughout the study.Interpretation High plasma RANKL and OPG levels at diagnosis of Charcot suggest that there is high bone remodeling activity before gradually normalizing after off-loading treatment. The consistently balanced OPG/RANKL ratio in Charcot patients suggests that there is low-key net bone building activity by this pathway following diagnosis and treatment. Inter-group differences at diagnosis and changes in Wnt signaling following off-loading treatment were sufficiently large to be reflected by systemic levels, indicating that this pathway has a role in bone remodeling and bone repair activity in Charcot patients. This is of particular clinical relevance considering the recent emergence of promising drugs that target this system.