Anatomy of the sacroiliac joints in children and adolescents by computed tomography

Background: diagnosing sacroiliitis by magnetic resonance imaging (mri) in children/adolescents can be difficult due to the growth-related changes. this study analyzed the normal osseous anatomy of the sacroiliac joints (sij) in a juvenile population using computed tomography (ct). methods: the anatomy of the sij was retrospectively analyzed in 124 trauma patients aged 9 months - <18 years by ct,based on 2 mm slices in axial,semi-axial and semi-coronal planes. the following anatomical features were recorded: intersegmental fusion of the sacral vertebral segments 1-3 (s1-s3),ossified nuclei (antero-superior at s1,lateral to the intervertebral spaces and lateral to s1 and s2) and joint facet defects larger than 3 mm. results: fusion of s1/s2 started at the age of 6 years and was complete after the age of 13 years in most girls and after the age of 14 years in most boys. fusion of s2/s3 started at the age of 9 years,but could remain incomplete up to 18 years in both genders. ossified nuclei antero-lateral at s1 and/or in the joint space were observed until the age of 18 years and occurred in 77% of individuals ≥13 years with intraarticular localization in 64% of girls and 60% of boys. joint facet defects >3 mm occurred in 21 children/adolescents (17%) located to both the iliac and sacral joint facets. conclusions: normal osseous sij structures in children and adolescents vary considerably. attention to these normal anatomical structures during growth may help to avoid false positive findings by mri. © 2017 the author(s).