MRI evaluation of the knee in children with infantile Blount disease: tibial and extra-tibial findings.

ABSTRACT

BACKGROUND: Infantile Blount disease is a developmental condition characterized by disorganized endochondral ossification in the medial aspect of the proximal tibial physis. OBJECTIVE: To describe the MR imaging abnormalities in the proximal tibia, distal femur, menisci and ligaments of children with infantile Blount disease. MATERIALS AND METHODS: We retrospectively evaluated 11 children (18 total knee MR examinations) with infantile Blount disease and compared them with an age-matched control group with normal MR examinations. Morphological and morphometric measurements were performed. RESULTS: The medial menisci were enlarged with increased T2 signal intensity in all MR examinations. The medial femoral epiphyseal cartilage showed abnormal foci of increased signal intensity in nine (50%). The mid-coronal thickness of the medial tibial epiphyseal cartilage was decreased with concomitant increase in the mid-coronal joint space distance. Angular measurements of the proximal tibia demonstrated posteromedial down-sloping configuration. CONCLUSIONS: Most severe abnormalities of infantile Blount disease occur in the medial compartment of the knee, especially at the medial tibial physis and epiphysis. However, other important structures of the knee and the lateral compartment are often affected. MR imaging helps to delineate the extent of multiple tibial and extra-tibial abnormalities, including meniscal abnormalities, perichondrial membrane changes and premature physeal closure.