Analysis of bone strength in ankylosing spondylitis patients with radiographic hip involvement / 中华风湿病学杂志

ABSTRACT

Objective:To analyze bone strength index, osteoporosis and fracture in ankylosing spondylitis (AS) patients with radiologic hip involvement and explore the characteristics of bone strength in these patients.Methods:According to bath ankylosing spondylitis radiology hip index (BASRI-hip) score, 339 AS patients were divided into two groups. The differences of bone strength in each group were analyzed by t-test, Mann-Whitney U test and χ2 test. Logistic regression was used to analyze the risk factors of bone strength index. The correlation between quantitative ultrasound and dualenergy X-ray absorptiometry (DXA) (total hip, g/cm 2) was analyzed. Pearson correlation analysis was used. Results:①Bone strength index of quantitative ultrasound was positively correlated with bone mineral density of DXA (total hip, g/cm 2), r=0.553, P<0.01. ② The age of 27(23, 37) years old in radiographic hip involvement was lower than 37(28, 48) years old in non-radiographic hip involvement, and the difference was statistically significant ( Z=-5.986, P<0.01). There were no differences in gender and course of disease between the two groups ( P>0.05).③ The radiographic hip involvement in AS patients whose ages were younger than 50, when compared with non-radiographic hip involvement patients, the bone strength index was lower (78±18 vs 84±16), while bone strength was lower than patients at the same age (41.0% vs 18.4%), however, the incidences of osteoporosis (42.7% vs 28.8%) and fragility fracture (3.7% vs 0%) were significantly higher ( t=3.028, P<0.01; χ2=16.758, P<0.01; χ2=5.886, P=0.019; χ2=4.67, P=0.038). For AS patients whose ages were ≥50, there were no significant differences between the two groups ( P>0.05). ④ Multivariate analysis showed that radiographic hip involvement [ OR (95% CI)=1.912(1.05, 3.48)], age [ OR (95% CI)=0.94(0.911, 0.97)] and body mass index (BMI) (kg/m 2) [ OR (95% CI) =0.875(0.807, 0.948)] were associated with lower bone strength. Conclusion:There is positive correlation between the bone strength index of quantitative ultrasound and bone mineral density of DXA. AS patients with radiographic hip involvement are characterized by decreased bone strength and are more likely to develop osteoporosis and fragile fractures. The risk factors of low bone strength are radiographic hip involvement, age and BMI.