FRI0133 Loss of Anterior Concavity of 1St Sacrum in Assessment of the Modified Stoke Ankylosing Spondylitis Spinal Score: MR Correlation
Authors: S. Lee, J.Y. Kim, K.B. Joo, J.-B. Jun, Y.B. Joo, S.-K. Kim, T.-H. Kim
Journal: Annals of the Rheumatic Diseases (2014)

<h3>Background</h3> In assessment of the modified Stokes Anklyosing Spondylitis Spinal Score (mSASSS), squaring is an important factor of scoring. However, the 1st sacrum (S1) is often underestimated in the assessment of mSASSS because it is difficult to evaluate squaring. Thus, we applied the concept of loss of anterior concavity to evaluate S1 score instead of squaring. <h3>Objectives</h3> This study aimed to evaluate usefulness and reliability of S1 scoring using the concept of loss of anterior concavity and to evaluate its relationships with mSASSS and MRI in ankylosing spondylitis. <h3>Methods</h3> The study group comprised 77 AS patients (67 males, 10 females; mean age 33.6 yrs) and 78 healthy controls (32 males, 46 females; mean age 56.3 yrs). Two experienced radiologists independently assessed the mSASSS on cervical and lumbar plain radiographies in AS groups and evaluated loss of anterior concavity of S1 in control and AS groups. And also, MR images were independently evaluated for signs of inflammation or structural changes of S1 in control and AS groups. S1 score between control and AS groups as well as its correlation with MR findings were statistically analyzed. <h3>Results</h3> According to reader 1, loss of anterior concavity in the control group was found in 7 sacrum (8.9%) and in the patients group was in 27 (35%) on plain radiography. According to reader 2, loss of anterior concavity in the control group was found in 5 sacrum (6.4%) and in the patients group was in 39 (50.6%) on plain radiography. Interobserver agreement in S1 score was found to be nearly perfect (κ value: 0.854) on plain radiography. S1 score was significantly correlated with changes on MRI in AS group by both radiologists (κ value: 0.74). In AS group, the interobserver agreements for total mSASSS was very good (0.99 with ICC). And S1 score was found to be significantly correlated with total mSASSS by both radiologists (p&lt;0.001). <h3>Conclusions</h3> Loss of anterior concavity in S1 is a useful concept to assess S1 scoring and shows good reproducibility. And it is well correlated with MR findings in AS group. Thus, we should not overlook loss of anterior concavity in S1 which would to predict early spinal involvement of AS. <h3>References</h3> Kim TJ, Kim HS, Joo KB, Kim S, Kim TH. Do we really need to evaluate entire cervical spines for squaring score in modified stoke ankylosing spondylitis spinal score? J Rheumatol. 2008 Mar; 35(3):477-9. Madsen KB, Jurik AG. MRI grading method for active and chronic spinal changes in spondyloarthritis. Clin Radiol. 2010 Jan; 65(1):6-14. Ward MM, Learch TJ, Weisman MH. Cervical vertebral squaring in patients without spondyloarthritis. J Rheumatol. 2012 Sep; 39(9):1900. Ralston SH, Urquhart GD, Brzeski M, Sturrock RD. A new method for the radiological assessment of vertebral squaring in ankylosing spondylitis. Ann Rheum Dis. 1992 Mar;51(3):330-3. Creemers MC, Franssen MJ, van9t Hof MA, Gribnau FW, van de Putte LB, van Riel PL. Assessment of outcome in ankylosing spondylitis: an extended radiographic scoring system. Ann Rheum Dis. 2005 Jan; 64(1):127-9. <h3>Acknowledgements</h3> Disclosure of Interest: None declared <h3>Disclosure of Interest</h3> None declared <h3>DOI</h3> 10.1136/annrheumdis-2014-eular.3085