Does Juvenile Idiopathic Arthritis Affect the Course of Legg–Calvé–Perthes Disease? A Case-Control Study with a Mean Follow-Up of 8 Years

Background: This study aimed to determine the clinical and radiological course in children who had Legg–Calvé–Perthes disease (LCPD) associated with juvenile idiopathic arthritis (JIA). Methods: In a retrospective chart review between 2007 and 2019, eight consecutive JIA patients diagnosed with concomitant LCPD were identified and compared with a case-control group of 10 children with LCPD only. Results: LCPD was diagnosed at a mean age of 8.1 years (3.0–14.7) in children with JIA as compared to 6.1 years (2.9–10.0) in controls. According to the modified Harris Hip Score (mHHS), four children with JIA and all controls had an excellent result. Regarding the fragmentation severity and the duration of each stage, we found no differences using the lateral pillar and modified Elizabethtown classification. Five hips were classified as Stulberg I/II, two hips as Stulberg III, and one hip as Stulberg V with no evidence of hip dysplasia or severe overcoverage in either group. Conclusions: The radiological outcome of LCPD did not differ between both groups, while the clinical outcome was slightly better in controls. Physicians should be aware that children with LCPD may have JIA too. In suspicious cases, further investigations are recommended, and patients should be referred to pediatric rheumatologists.