The Radiographic Study Of Hip Lesion In Patients With Juvenile-onset Ankylosing Spondylitis

PurposeTo analyze the radiographic feature of hip lesion in patients with Juvenile-onset Ankylosing Spondylitis (JAS). To study the relationship between the radiographic lesion of hips and that of the lower part of axial joints, gender, age at onset, duration of disease. Objects and Methods71 patients who have been diagnosed with JAS were took pelvis and lumbar radiographs; 19 patients as control group were took pelvis radiographs. Each set of radiographs was read and analyzed twice respectively by three radiologists in blinded reading, finaly reaching a consensus. According to BASRI and the 1984 modification of the New York criteria, scored the lumbar spine, sacroiliac joint, hip images. Measured the diameters of acetabulums and femoral heads directly on the X-ray films.ResultsThe chief X-ray manifestation of hip lesion in patients with JAS were hip joint spaces narrowing (25.35%), osteophyte formation at the base of femoral heads (22.54%), cystic degeneration of acetabulums (21.83%), cystic degeneration of femoral heads (19.01%), osteophyte formation of acetabulums (16.20%), acetabular white lines discontinuity (14.08%). The patients with bilaterals hips involvement accounted for 35.21%, and the patients with unilateral hip involvement accounted for 2.82%. The hips with two or more than two kinds of lesion accounted for 28.87%, and the hips with only a single type of lesion accounted for 7.75%. Cystic degeneration of acetabulums and femoral heads had the strongest consistency in showing hip lesion (k=0.85, P<0.01). There were positive correlation between hip lesion grade and lumbar spine lesion grade, sacroiliac joint lesion grade, lower axial joint lesion grade (r=0.51, r=0.41, r=0.49 and P<0.01). The percentages of patients with high-grade hip lesion were no significant difference between the male group and the female group (P>0.05), also between the early age of onset group and the late age of onset group (P>0.05). There was no significant correlation between the grade of hip joint lesion and the age of onset (P>0.05). The grade of hip joint lesion was positively correlated with the disease duration (r=0.28, P<0.05). There were no significant difference in the age of onset distributions between the group with low-grade hip lesion and the group with high-grade hip lesion (P > 0.05). There were significant difference in the distributions of disease duration between the group with low-grade hip lesion and the group with high-grade hip lesion (P<0.01). In logistic regression analysis, disease duration was a risk factor of hip lesion (OR=1.11, P<0.05). The means of the ratios by the acetabulum diameter compareing the femoral head diameter (mean SD, 1.06 0.06 and 1.10 0.05) had significant difference (P<0.01) between the group with high-grade hip lesion and the group with low-grade hip lesion. The means of the ratios by the acetabulum diameter compareing the femoral head diameter (mean SD, 1.10 0.05 and 1.14 0.04) had significant difference (P<0.01) between the group with low-grade hip lesion and the control group. ConclusionThe common X-ray findings of hip lesion in patients with JAS were hip joint space narrowing, osteophyte formation at the base of the femoral head, cystic degeneration of acetabulum and femoral head, osteophyte formation of acetabulum. Bilateral hips involvement was more common than unilateral hip involvement. The hips which involed were often had two or more than two kinds of lesion. Cystic degeneration of acetabulums and femoral heads had the strongest consistency in showing hip lesion. The lesion of hips and that of lumbar spines, that of sacroiliac joints were in a synchronous trend of progress. The radiographic change and development of sacroiliac joints and lumbar spines could generally reflect the existence and process of hip lesion. The relationship was not close between hip lesion and gender, age at onset in patients with JAS. Disease duration was a risk factor of hip lesion. With the progress of hip lesion, the femoral heads became bigger and did not match with the acetabulums.