Acute fracture of the distal tibial physis: role of gradient-echo MR imaging versus plain film examination.

OBJECTIVE: Recent reports indicate that, compared with MR imaging, plain film radiography often underestimates the extent of injury in children with physeal fracture-separation. Such underestimation may have significant therapeutic and prognostic outcomes. We performed this study to assess the benefit of MR imaging compared with plain film radiography in the diagnosis and immediate treatment of acute fractures of the distal tibial physis.

SUBJECTS AND METHODS: Twenty-nine patients with acute fractures, including 15 Salter-Harris II, four Salter-Harris III, four Salter-Harris IV, and six triplane fractures, were prospectively examined by MR imaging with gradient-echo sequences. The MR images were compared with plain film radiographs. All cases were reviewed in a blind fashion by two experienced radiologists to determine the Salter-Harris classification on the basis of first plain film radiographs and then MR images. Two experienced pediatric surgeons were asked to propose treatment on the basis of first plain film radiographs and then MR images. Both the radiologists and the surgeons were asked to rate the two techniques in terms of degree of confidence and overall diagnostic effectiveness.

RESULTS: Only 1 or 29 fractures (3%) was misclassified by plain film radiography. MR imaging never caused the treatment plan to be modified. However, the position of fracture fragments in Salter-Harris IV and triplane fractures was always better appreciated on MR images, facilitating more accurate surgical treatment. Except for those in the misclassified fracture, all other fracture lines were seen on both plain film radiographs and MR images but were more easily seen on MR images.

CONCLUSION: Gradient-echo MR imaging allowed easier assessment of fracture lines than did plain film radiography, but the latter technique remains the primary means of evaluating epiphyseal injuries. For acute fractures of the lower extremity of the tibia, gradient-echo MR imaging should be limited to complex fractures and to cases in which the classification of a fracture on the basis of plain film evaluation is uncertain.