Ultrasonography Of The Hip Joints In Patients With Ankylosing Spondylitis

Objective: Through the early changes of the hip joints in patients with ankylosing spondylitis (AS) by ultrasonography (US), including the comparison with the radiography, as well as the relationship with the hip pain, the erythrocyte sedimentation rate (ESR), C reactive protein (CRP) and HLA-B27, to explore the diagnosing significance of US in the hip joint involved in AS in the early stage.Methods: 53 patients with AS underwent independent clinical and US examination of both hip joints in anterior longitudinal scan. The US examination was performed using HP-5500 (USA) with linear-transducers, 3-11 MHz to examine the cartilage of the femoral head and 2-6 MHz to examine the anterior collum-capsule distance (CCD). The bone structure was observed at the same time. 20 healthy volunteers were selected as the normal control (NC) group. T-test, x2-test and Fisher's exact test of probabilities were applied in statistical analysis. A value of P<0.05 was required for statistical significance.Results: 1.The thickness of the cartilage is 0.6236±0.2136mm in AS group and 0.8900 +0.0928mm in NC group. The CCD is 7.5396±2.1501mm in AS group and 5.8405 ± 0.4719mm in NC group. The differences both are of statistical significance (P<0.05). 2.In AS patients, the thickness of the cartilage is 0.5985 ±0.2388mm in painful joints and 0.6634±0.1609mm in painless ones. There is no difference between them (p>0.05). The CCD is 7.0354 ± 1.8874mm in painful joints and 8.3512 ±2.3265mm in painless ones. The difference is significant (p<0.05). In contrast to NC group, both the thickness of the cartilage and the CCD of either painful or painless joints have statistical difference (p<0.05). 3.The incidence of hip joint involved in AS is 56.8% in HLA-B27 positive patients and 55.6% in HLA-B27 negative patients. There is no difference between them (p<0.05). 4.In AS group, the ESR is 47.8333 ±31.5443mm/h in patients with abnormal interval by US and 28.9565 ±23.0049mm/h in patients with normal interval by US. The CRP is 55.4487 ± 49.3322mg/l in patients with abnormal interval by US and 20.7665 ± 14.7701mg/l in patients with normal interval by US. Both differences are of statistical significance (p<0.05). 5.Of 53 AS patients 30 were found to have inflammatory changes of hip joints by US, in which 13 were found to have bone erosion. While only 5 patients were found to have bone erosion by X ray. The difference is significant (p<0.05).Conclusion: 1. In comparison with the NC group, the thickness of the cartilage of the femoral head in AS patients decreases (P<0.05) and the CCD increases (P<0.05). 2. There is no difference in the thickness of the cartilage between painful and painless joints. The CCD of the painful joints is thinner than painless ones. The cartilage of both the painful and painless joints is thinner than that of NC group. The CCD of both is larger than that of NC group. 3. The incidence of hip joint involved in AS patients is irrelevant to HLA-B27. 4. The ESR and CRP increase significantly in patients with abnormal interval by US compared with those in patients with normal interval by US. 5. US is superior to radiography in the ability of exploring the inflammatory changes of the hip jointsincluding the bone erosion. US may be used to explore the early inflammatory changes of the hip joints in AS patients.