Stress injuries of bone: Analysis of MR imaging staging criteria

Rationale and Objectives. The authors examined the prognostic value of magnetic resonance (MR) imaging in stress injuries of bone. Materials and Methods. Clinical follow-up data were collected in 35 patients who underwent MR imaging because of suspected stress fractures. MR findings were correlated with total duration of symptoms, the time to return to sports activity, and findings at follow-up radiography. Results. The MR imaging finding of a 'fracture' or 'fatigue' line or a cortical signal intensity abnormality was predictive of a longer symptomatic period, whereas muscle edema was predictive of a shorter symptomatic period. A published grading system could be used in only 24 patients; the MR imaging grade of injury did not show correlation with clinical outcome. Conclusion. The MR imaging finding of either a medullary line or a cortical abnormality appears to indicate a more severe stress injury of bone. A previously published MR imaging grading system for stress injuries of the tibia was not prognostic in this more heterogeneous patient group.