Longitudinal stress fractures of the tibia: diagnosis by magnetic resonance imaging.

OBJECTIVE: Previous works describe magnetic resonance (MR) imaging characteristics of stress fractures. Diagnosis of the atypical, longitudinal type of stress fracture has been reported using computed tomography (CT). This report focuses on MR imaging of longitudinal stress fractures of the tibia.
MATERIALS AND METHODS: Six cases are presented in which a longitudinal linear abnormal marrow signal was detected in the middle and distal parts of the tibial shaft. Five patients were imaged using a 1.5 Tesla MR unit. Axial, sagittal and coronal T1 and T2-weighted or fat suppressed proton density fast spin echo images were obtained in all but one patient. One patient was imaged using a 0.5 Tesla MR unit with axial and coronal T1- and T2-weighted sequences. Initial conventional radiographs seen at clinical presentation were interpreted as normal in all cases. Two patients underwent radionuclide bone scan. and one patient was imaged with CT prior to MR imaging.
RESULTS: In each instance, MR imaging demonstrated linear marrow signal abnormalities orientated along the long axis of the tibial shaft. Endosteal and periosteal callus was identified on axial images. In all cases, MR imaging clearly demonstrated a fracture extending through one cortex with abnormal signal in both the marrow cavity as well as adjacent soft tissues indicating edema.
CONCLUSION: MR imaging was shown to be excellent for demonstration of fracture lines, callus, and marrow and soft tissue abnormalities seen in association with longitudinal stress fractures.