Metaphyseal changes on whole-body magnetic resonance imaging following bisphosphonate therapy in children with chronic nonbacterial osteomyelitis: distinguishing treatment effect from disease flare

BACKGROUND: Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory disease that often affects the metaphyses. Bisphosphonates, a second-line therapy, can cause bone marrow changes that may mimic active disease. OBJECTIVE: To characterize metaphyseal long-bone marrow changes on whole-body MRI (WB-MRI) following bisphosphonate therapy in children with CNO and evaluate if they can be distinguished from active disease. MATERIALS AND METHODS: Retrospective study (2015-2025) included children with CNO treated with bisphosphonates and age- and sex-matched untreated controls. Two blinded pediatric radiologists independently evaluated long-bone metaphyses for CNO and bisphosphonate treatment effects classified as symmetric sclerotic bands, alternating high-signal and sclerotic bands, or predominantly high-signal bands. Associations with treatment, number of infusions, and intervals from the first to most recent infusions were evaluated, accounting for repeated examinations. RESULTS: Twenty-one treated children (median age 10.7 years, 12 females) underwent 30 pretreatment and 51 post-treatment WB-MRIs; 21 controls (median age 10.0 years, 12 female) underwent 48 examinations. Bisphosphonate-related changes occurred in 85.7% (18/21) treated children versus 14.3% (3/21) controls (P<0.001). Sclerotic bands alone occurred in 23.8% versus 14.3%. Alternating high-signal-intensity and sclerotic bands (38.1%) and predominantly bright signal bands (23.8%) occurred exclusively after treatment. High signal was associated with more infusions (P<0.001) from the most recent (P<0.001) and first (P=0.027) infusions and was most common around the knee and distal tibia. CONCLUSION: Symmetric metaphyseal high-signal stripes are a dose- and time-related bisphosphonate treatment effect and should not be misinterpreted as active CNO. Sclerotic bands alone are not specific for treatment.