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Fractures associated with ACL injury need to be taken seriously
  1. Ali Guermazi1⇑,
  2. Frank W Roemer1,2,
  3. Kay M Crossley3,
  4. Michel D Crema1,4,5
  1. 1 Department of Radiology, Boston University School of Medicine, Boston, Massachusetts, USA
  2. 2 Department of Radiology, University of Erlangen-Nuremberg, Erlangen, Germany
  3. 3 College of Science, Health and Engineering, La Trobe University, Melbourne, Victoria, Australia
  4. 4 Department of Radiology, Saint-Antoine Hospital, Paris VI University, Paris, France
  5. 5 Department of Sports Medicine, French National Institute of Sport (INSEP), Paris, France
  1. Correspondence to Professor Ali Guermazi, Department of Radiology, Boston University School of Medicine, 820 Harrison Avenue, FGH Building, 3rd floor, Boston, MA 02118, USA; ali.guermazi{at}bmc.org

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Have you missed a fracture associated with an ACL injury? Plain radiography generally fails to detect subchondral fractures around the knee associated with ACL tears.1 However, those fractures are frequently seen on MRI in patients with acute ACL tear.

When radiologists report ‘fractures’ based on MRI findings, they refer to a very different entity than bone bruises, traumatic bone marrow oedema or contusion, which all refer to an identical image finding—an ill-defined signal alteration without definite evidence of a fracture line. On MRI, a fracture is defined as a dark (low signal intensity) line on the different pulse sequences acquired, commonly surrounded by bone marrow oedema. These ‘dark lines’ are usually better depicted using T1-weighted image without fat suppression (figure 1). When using MRI to assess the knee, such fractures are present in as many as 60%–72% of knees after an acute ACL tear.2 3

Figure 1

Tibial fracture associated with complete ACL tear after hyperextension mechanism. (A) Sagittal proton density-weighted fat-suppressed MRI shows a complete disruption of the ACL near its femoral attachment (arrow). (B) Corresponding sagittal proton density-weighted fat-suppressed …

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