Imaging of bone micro-injuries

PURPOSE: We evaluated the fundamental signs of each imaging modality to define the role of MRI in identifying and characterizing bone micro-injuries. MATERIALS AND METHODS: We retrospectively reviewed 50 MRI examinations performed after preliminary conventional radiography on 25 stress fractures and 25 insufficiency fractures between 1989 and 2002. The number of lesions identified was 55: 11 were evaluated with CT and 9 with radionuclide bone scan. RESULTS: Although bone micro-injuries have different pathogenetic mechanisms, the final outcome is a cortical and/or spongy bone fissure, followed by repair processes. Conventional x-ray showed the presence of a lesion in 24/55 cases. Radionuclide bone scanning allowed suspicion or confirmation of the lesion in 8/9 cases. MR identified the lesion in all cases. CT allowed recognition of the lesion in 10/11 cases. CONCLUSIONS: When a bone micro-injury is suspected following conventional radiography, MRI is the most sensitive and specific modality able to complete the diagnostic work-up.