Measurement of red bone marrow changes in pediatric ankle Magnetic resonance imaging

Aim Magnetic resonance imaging (MRI) examinations of the ankle in the pediatric age group frequently show high signals on T2-weighted images (T2A). Differential diagnoses of these high signals include bone marrow oedema, trauma, inflammation, infection, neoplastic causes, arthritis, metabolic causes, iatrogenic, biomechanical and developmental causes. T2A focal signal increases in pediatric ankle MRI may also indicate red bone marrow changes, which is a physiological finding. The main aim of this study is to understand that focal T2A hyperintensities in pediatric ankle MRI examinations may belong to red bone marrow changes as well as differential diagnoses indicating pathology, and to understand in which bones, how often they are observed, and how they are distributed with age and gender. In this way, the normal patterns of red bone marrow changes and bone marrow transformation will be understood and it will be possible to distinguish the signal changes observed in pediatric ankle MRI from other differential diagnoses. Materials and Methods Our study was performed retrospectively in pediatric patients aged 18 years and younger who underwent ankle imaging on 1.5 Tesla MRI device in the Radiology Clinic of Erzincan Binali Yıldırım University Mengücek Gazi Training and Research Hospital between October 2020 and October 2024. Patients with anamnesis or findings consistent with osteomyelitis, trauma, primary tumour and metastatic lesion, metabolic and developmental anomaly, treatment-related changes were excluded from the study. A total of 196 patients were analysed according to the specified principles and 47 patients were excluded from the study. The study population consisted of 149 patients. In the ankle MRI examinations of the patients included in the study, it was recorded whether T2A signal increases consistent with red bone marrow changes were observed, if these signals were observed, in which bones they were present, in which foot the imaging was performed, age and gender of the patients. Results Foci or foci in at least one of the bone structures consistent with red bone marrow changes were observed in 125 (83.9%) of 149 patients included in the study. Foci consistent with red bone marrow changes were detected in 81.2% of the patients in the talus, 57.7% in the calcaneus, 47% in the navicular, 32.2% in the cuboid bone, 38.9% in the medial cuneiform, 30.9% in the middle cuneiform, 19.5% in the lateral cuneiform, 18.1% in the metatarsal base, 18.8% in the tibia, and 12.8% in the fibula. The frequency of foci was lower with advancing age. In anatomical groupings of the foot bones, the frequency of foci compatible with red bone marrow changes was higher in the hindfoot and medial aspect of the foot. In school-age girls, the frequency of foci consistent with red bone marrow changes in the tibia, fibula and metatarsal base was higher than in boys, whereas the frequency of foci consistent with red bone marrow changes in other regions was higher in boys. In the adolescent group, the frequency of foci consistent with red bone marrow changes was higher in boys compared to girls in all bones. Conclusions The frequency of foci consistent with red bone marrow changes decreases with age. In our study, in agreement with the pattern of bone marrow conversion described in the literature, foci compatible with red bone marrow changes were observed in an increasing order of frequency from distal to proximal and were most frequently observed in the hindfoot group. In addition, as a contribution to the literature, as a result of the comparisons made in male and female gender groups in our study, the frequency of foci compatible with red bone marrow changes was found to be higher in the male gender group. Another contribution to the literature is that when the foot was anatomically divided into lateral and medial groups, the frequency of foci compatible with red bone marrow changes was higher in the medial group than in the lateral group. Key Words: Bone Marrow MRI, Bone Marrow Conversion, Reconversion, Red Bone Marrow changes, Ankle MRI