Comparison Of Bone Mineral Density In Different Anatomical Locations Of Ankylosing Spondylitis Patients And Its Clinical Significance

Part one:Comparison of bone mineral density in different anatomical locations of ankylosing spondylitis patients and its clinical significanceObjective:To compare the bone mineral density (BMD) in different anatomical locations of ankylosing spondylitis (AS) patients.Methods:From February 2013 to July 2013,27 AS patients (25 males and 2 females) were included, with the mean age of 32.3±10.2 years (18 to 55 years) and the average disease duration of 10.2±7.1 years (3 to 25 years). The BMD was measured by the dual-energy X-ray absorptiometry (DEXA). The Z-scores of BMD in lumbar spine (L2-L4), femoral neck and radius of forearm were measured and recorded. The lumbar radiological scores were evaluated on the full-length standing antero-posterior and lateral spine radiographs, according to the modified Stoke ankylosing spondylitis spine score (mSASSS) and the Bath ankylosing spondylitis radiology index-spine (BASRI-s). According to the disease duration, the patients were divided into group A (early stage group, disease duration< 10 years) and group B (late stage group, disease duration≥10 years). The Z scores of BMD at lumbar spine, femoral neck and radius of forearm were compared to determine which was the most sensitive in detecting bone loss in AS patients. The correlation between the age, the disease duration, the radiological scores and the Z scores of BMD were analyzed by the Pearson correlation.Results:In group A, the Z scores of BMD in lumbar spine (L2-L4), femoral neck and radius of forearm were-2.1±1.6 s,-1.6±1.1 s and-0.4±0.4 s, respectively; in group B, the Z scores of BMD in lumbar spine (L2-L4), femoral neck and radius of forearm were 1.1±1.4 s,-1.4±1.2 s and-0.7±0.9 s, respectively. The Z scores of BMD in lumbar spine were significant different between group A and group B (p< 0.05). The Z scores of BMD in femoral neck and radius of forearm showed no significant difference between the two groups (p> 0.05). In group A, the patients had a lower BMD at lumbar spine and it was more sensitive in detecting bone loss in AS patients.In contrast, the lumbar BMD increased in group B, and the BMD at the femoral neck was more sensitive in detecting bone loss in AS patients. The radiological scores of mSASSS and BASRI-s for lumbar spine were significantly different between group A and group B. The radiological scores of mSASSS and BASRI-s for lumbar spine were strongly correlated with the BMD of the lumbar spine but they were not correlated with the BMD of the femoral neck and the radius of forearm in AS patients.Conclusion:The BMD of the lumbar spine was more accurate in detecting bone loss in the early-stage AS patients, while in the late-stage AS patients, the BMD of the femoral neck was more precise. With the disease duration increased, the BMD of the lumbar spine increased with the osteophytes and bone bridge formation, while the BMD of the femoral neck and the radius of forearm were not changed.Part two:Correlation analysis of thoracolumbar kyphosis and hip involvement in ankylosing spondylitis patientsObjectives The purpose of this study is to determine the risk factors of hip involvement in ankylosing spondylitis (AS) patients with thoracolumbar kyphosis.Methods Sixty-six consecutive AS patients (group A:fifty AS patients with thoracolumbar kyphosis and group B:sixteen AS patient without with thoracolumbar kyphosis) were included in this study. There were 58 males and 8 females, with an average age of 31.2years (range,17-53 years). The clinical data, the laboratory data, the radiographical data, and three quality of life questionnaires were recorded. The clinical data included age and disease duration. The laboratory data included erythrocyte sedimentation rate (ESR), C-reaction protein (CRP), and HLA-B27. The radiographical data included global kyphosis angle (GK) and bath ankylosing spondylitis radiology index-hip score (BASRI-hip). Three quality of life questionnaires consisted of bath ankylosing spondylitis disease activity index (BASDAI), bath ankylosing spondylitis functional index (BASFI), and Oswestry disability index (ODI). Hip involvement was defined as BASRI-hip score greater than 2 (group C:the patients with hip invovlement and group D:the patients without hip invovlement). The independent-samples t test was used between group C and group D. The spearman correlation test was used to investigate the risk factors correlated with hip involvement in group A. Then the multivariate regression analysis was used to found the high risk factors with hip involvement.Results Twenty-seven (54%) AS patients in group A and 3(19%) AS patients in group B had radiographical evidence of hip involvement (OR=5.08). By the multivariate regression analysis, GK and disease duration were the high risk factors of radiographical hip involvement in AS patients with thoracolumbar kyphosis. BASFI score was significantly correlated with hip involvement and GK(r=0.345, P<0.014;r=0.352, P<0.012).Conclusion Larger GK and longer disease duration are high risk factors of radiographical hip involvement in AS patients with thoracolumbar kyphosis. Patients with larger GK and hip involvement impaired the quality of life in AS.