[Preoperative assessment of Blount disease].

Osteochondrosis of the medial proximal tibial epiphyseal plate is known as Blount disease. To date, two types have been described: infantile and juvenile disease. Six patients (5 men and 1 woman, mean age: 7.2 years) affected with infantile Blount disease diagnosed with plain radiography were submitted to Magnetic Resonance Imaging (MRI) for preoperative lesion staging. The lesions were bilateral in 5 patients. According to Langenskiöld classification, 2 patients were in stage II-III, 3 in stage III-IV and 1 in stage V-VI. Each patient underwent MRI of the more affected knee and 1 patient, who exhibited a more prominent metaphyseal beak, underwent CT of both knees. MRI depicted proximal tibia varus deformity and the degree of its angulation, which helped plan osteotomy; impaired growth of the medial portion of the proximal tibia involving physeal cartilage, metaphysis and epiphysis; alterations of menisci and ligaments (hypertrophic medial meniscus, medial collateral ligament laxity), the presence of bone bridges; the presence and integrity of unossified epiphysis and of chondral growth plate which was quite completely ossified in one case. To conclude, MRI is a completely atraumatic and noninvasive technique yielding many pieces of information necessary for the preoperative assessment of Blount disease.