MR imaging of normal epiphyseal development and common epiphyseal disorders

During infancy and childhood, multiple developmental changes occur in the epiphysis. Initially the epiphysis is composed entirely of hyaline cartilage. As skeletal maturation progresses, one or several secondary ossification centers (SOCs) develop within the epiphyseal cartilage. The SOCs enlarge by endochondral ossification and undergo marrow transformation in a process analogous to that of the primary physis and metaphysis. Magnetic resonance (MR) imaging can be used to evaluate vascularity, marrow, and cartilage and plays a critical role in the assessment of epiphyseal disorders in children. In cases of shoulder and hip dysplasia, MR imaging demonstrates unossified structures and helps guide treatment. In cases of trauma, the intracartilaginous pathway of fractures, the degree of physeal involvement, and early bridge formation can be assessed. With the use of intravenous gadolinium-based contrast material, avascular necrosis and reperfusion can be characterized. This article reviews the normal structure of the epiphysis, its appearance at MR imaging, and age-related changes to the epiphysis. Common conditions that lead to epiphyseal damage in children are reviewed, with an emphasis on the role of MR imaging in diagnosis, prognosis, and treatment.