MRI and sonography in Legg-Calvé-Perthes disease: clinical relevance of containment and influence on treatment.  Journal of Children’s Orthopaedics, 2018 October Jandl NM, Schmidt T, Schulz M, Rüther W, Stuecker MHF In a recent study, ultrasound measurements were correlated with magnetic resonance imaging (MRI) measurements to evaluate the utility in determing how contained the femoral head was in the acetabulum (hip socket). In Perthes disease, one of the goals of treatment is containment of the femoral head in the acetabulum.  In children affected with Perthes disease, much of the femoral head is cartilage before it turns into bone.  The difficulty in assessing the true amount of containment on xrays is that the cartilage of the femoral head is not visible on xrays.  MRI clearly shows the hip cartilage, though there can be challenges with MRI including the need for sedation in young children, and cost.  An advantage of ultrasound is that it is non-invasive, does not require sedation,