Background In radiographic evaluation of ankylosing spondylitis (AS) patients, it was well known that the principle sites of involvement are the sacroiliac joints with spine and symphysis pubis joint involvement is very rare [1,2]. But several recent studies suggest that symphysis pubis joint changes of AS patients are frequently seen on pelvic MRI [3,4].
Objectives The purpose of this study is to evaluate the proportion of symphysis pubis joint involvement in ankylosing spondylitis (AS) patients and to find out the correlation between symphysis pubis joint change and the modified Stoke spinal score (mSASSS).
Methods A retrospective evaluation was performed in 222 AS male patients who had pelvis radiograph with cervical and lumbar spine radiographs in Hanyang University Hospital for Rheumatic Diseases from Aug 2004 to Feb 2014. The radiographs were examined by two experienced radiologist and evaluated according to the radiographic damage score: 0 - no damage, 1 - subtle irregularity and subchondral sclerosis, 2 - erosion, 3 - ankylosis or 4 - total ankylosis. We evaluated clinical characteristics of AS patients and analyzed radiologic changes. The relationship between symphysis pubis joint damage score and mSASSS in two different time points was investigated using generalized estimating equations (GEE).
Results The mean age of AS patients was 30.6±8.3 years and the mean disease duration was 7.1±4.6 years. Among them, 105 patients (47.3%) showed radiologic damage in symphysis pubis joint. In comparison between normal group (score 0) and abnormal group (score 1-4) of symphysis pubis joint, abnormal group showed longer symptom duration (10.1±7.0 vs 7.6±5.8 years, p=0.004) and higher mSASSS (18.6±17.0 vs 14.3±13.4, p=0.038) than normal group. A significant Pearson correlation was found between the radiographic damage score of symphysis pubis joint and mSASSS (r=0.205, p=0.020). Using GEE analysis, an increase of one symphysis pubis joint damage score led to an increase of 16.7 mSASSS units (p=0.029).
Conclusions The proportion of symphysis pubis involvement in AS male patients was 47.3%. Moreover, the radiographic change of symphysis pubis was correlated with radiographic damage of spinal joint.
Calin A, Elswood J. The relationship between pelvic, spinal and hip involvement in ankylosing spondylitis–one disease process or several? Br. J. Rheumatol. 27, 393–395 (1988).
Vinson EN, Major NM. MR imaging of ankylosing spondylitis. Semin. Musculoskelet. Radiol. 7, 103–113 (2003).
Jans L, Van Langenhove C, Van Praet L, et al. Diagnostic value of pelvic enthesitis on MRI of the sacroiliac joints in spondyloarthritis. Eur. Radiol. 24, 866–871 (2014).
Yilmaz MH, Ozbayrak M, Kasapcopur O, Kurugoglu S, Kanberoglu K. Pelvic MRI findings of juvenile-onset ankylosing spondylitis. Clin. Rheumatol. 29, 1007–1013 (2010).
Disclosure of Interest None declared