Comparative study of radiography, CT and MRI in the identification of hip involvement in patients with ankylosing spondylitis

Abstract

Objective To study the imaging findings of hip involvement and to compare the sensitivity of radiography,CT,and MRI in the identification of hip involvement in patients with ankylosing spondylitis(AS).Methods Anteroposterior radiography of the pelvis and MRI of hip were performed in 55 patients with AS.CT scan of hip was performed in 29 of 55 patients.T1-weighted,T2-weighted,short tau inversion recovery (STIR) and three dimensional balanced turbo field echo with water selective excitation (3D-BTFE-WATS) coronal sequences of hips were obtained in all patients,of which fat-saturated contrastenhanced T1-weighted sequence was performed in 24 patients.The imaging data of 55 patients were analyzed.The chi-square test was used to analyze the sensitivity in the identification of hip involvement among radiography,CT,and MRI.Results Among 110 hips in all 55 patients,abnormal changes were detected in 13 hips by radiography,85 hips by MRI.The findings of radiography included bone erosions in 13 hips,joint space narrowing in 4 hips,syndesmophytes in 5 hips.MRI revealed bone erosive destruction in 31 hips,joint space narrowing in 4 hips,joint effusion in 80 hips,subchondral bone marrow edema in 32 hips,fat accumulation of bone marrow in 28 hips,enthesitis in 21 hips.Bilateral synovial enhancement was showed in 19 of 24 patients who underwent fat-saturated contrast-enhanced T1-weighted sequence.Of the 58 hip joints in 29 patients who underwent CT examination,not only did CT show all bone erosions detected by radiography and MRI,but CT revealed bone erosive destruction that were not identified by radiography in 10 hips and by MRI in 1 hip as well.Abnormal changes were detected in 10.3％ (6/58)by radiography,27.6％ (16/58) by CT,and 77.6％ (45/58) by MRI.The sensitivity of MRI in the identification of hip involvement is higher than that of radiography and CT ( x2 =53.22 and 29.08,P ＜ 0.05 ).In addition to chronic bone structural changes,MRI depicted acute inflammatory changes which could not be detected by radiography and CT.Conclusions MRI can detect early acute inflammatory changes of hip joint that can not be showed by radiography and CT.Effusion of joint and synovial enhancement caused by synovitis are the most common MRI findings of the hip in patients with AS. Key words: Spondylitis, ankylosing; Hip joint; Magnetic resonance imaging; Tomography,X-ray computed; Radiography