Objectives There is considerable delay in the diagnosis of ankylosing spondylitis (AS) mostly due to the slow development of radiographic sacroiliitis. In a previous multi-center study we showed that approximately 1/3 of the AS patients had been diagnosed as lumbar disc herniation (LDH), and 7% had operation history for LDH. Moreover, prior history of LDH, and past history of surgery for LDH were independent predictors for the delay in diagnosis. In this study, we aimed to evaluate the frequency of AS and spondyloarthritis (SpA) in patients who had been surgically treated for LDH.
Methods We retrieved the records of the patients who underwent LDH surgery between 2008 and 2010, in the neurosurgery clinic of our university hospital. Eligible patients were then invited to the rheumatology clinic for further evaluation. All patients were examined according to a standard protocol to capture patients with SpA and AS. A face to face interview by using a standardized questionnaire was performed to obtain demographic and clinical features of SpA. Standard pelvic X-rays were performed in all patients to assess the sacroiliac joints (SIJ). The modified New York criteria (mNY) was used for the diagnosis of AS, and Amor and the European Spondyloarthropathy Study Group (ESSG) criteria were used for the classification of SpA. A telephone interview was performed by using the same questionnaire for patients who could not come to the outpatient clinic.
Results We detected 789 patients who underwent LDH surgery in this time period. We could not reach 468 patients (59%) despite at least two contact attempts by telephone. With the remaining 321 patients (142 male [44.2%], mean age 49.7±10.8 years) a face to face (n=123) or telephone interview (n=198) was performed. Face to face and telephone interview groups had similar age, sex distribution and symptom duration. However, education level was significantly higher in the face to face interview group (9.0±4.4 years vs. 7.1±4.1 years; p<0.001) and they reported ongoing pain after surgery more frequently (68% vs. 51.7%; p<0.001). The mean age at the onset-of low back pain was 34.4±12.5 years and at LDH diagnosis was 41.6±12.4 years. IBP was present in 108 patients (33.6%) according to the Calin and in 51 patients (16.4%) according to the Berlin criteria. Plain pelvic radiographs were performed in 308 patients and 5 (1.6%) of them had unequivocal sacroiliitis and were classified as having AS according to the modified New York criteria. The MRI of sacroiliac joints could be obtained in 12 out of 34 patients who had IBP but not radiographic sacroiliitis. Four patients had bone marrow edema in MRI examination in accordance with the Assessement of Spondyloarthritis International Society (ASAS) definitions. The overall prevalence of radiologic sacroiliitis (MRI sacroiliitis + X-ray sacroiliitis) was found 2.9% ((5+4)/308). The prevalence of SpA was estimated as 17.7% (57 patients) and 8.7% (28 patients) according to the ESSG and Amor criteria, respectively.
Conclusions The relatively high prevalence of AS and SpA among patients who had undergone LDH surgery indicates the necessity of increasing awareness about the concept of axial SpA of the specialists dealing with low back pain.
Disclosure of Interest None Declared
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