Inflammatory Changes of the Lumbar Spine in Children and Adolescents With Enthesitis-Related Arthritis: Magnetic Resonance Imaging Findings

OBJECTIVE To describe and profile abnormalities of the lumbar spine in a cohort of patients with enthesitis-related arthritis (ERA) as compared to a control group of adolescents with mechanical back pain. METHODS We performed a retrospective review of magnetic resonance imaging (MRI) lumbar spine scans of 79 patients (58 cases, 21 controls). The study was covered by institutional review board approval and informed consent was obtained for review of all clinical investigations. Images were reviewed by an expert MRI reader who was blinded to clinical details. The presence or absence of morphologic features of enthesitis, apophyseal joint synovitis, and inflammation of posterior elements was assessed at each lumbar vertebral level. The apophyseal joint inflammation was graded from 0 to 3 using a grading system that was adapted from one used in adults with inflammatory facet osteoarthropathy. STATA software was used for data analysis. RESULTS One or more abnormalities of the lumbar spine were found in 39 (67%) of 58 cases and sacroiliitis was present in 45 (78%) of the cases. Apophyseal joint synovitis was seen in 22 (38%) cases and in 1 (5%) control patient. This difference was highly significant (P = 0.004). Inflammatory changes in the interspinous ligaments were seen in a higher percentage of cases than controls and this observation was of statistical significance (P = 0.04). CONCLUSION Statistically significant inflammation of the lumbar apophyseal joints and interspinous ligaments was seen in our cohort of ERA patients, most of whom have concurrent sacroiliitis. This could be contributing to back pain in these patients.