From the Guidelines
A radiologist might misdiagnose a Salter-Harris type I lateral fracture as a bone bruise on MRI because these fractures can be subtle and challenging to detect, and both conditions can present with similar bone marrow edema patterns on imaging, as noted in the ACR Appropriateness Criteria for acute trauma to the ankle 1. When evaluating ankle injuries, particularly in pediatric patients, it's essential to consider the limitations of MRI in detecting Salter-Harris type I fractures. These fractures occur through the growth plate (physis) without involving the adjacent bone, and they may not show visible displacement on imaging. According to the ACR Appropriateness Criteria, MRI is the reference standard for ligamentous injury and assessment of stability, but it may not always detect Salter-Harris type I fractures, especially if the growth plate remains anatomically aligned 1. Some key points to consider in differentiating between bone bruises and Salter-Harris type I fractures include:
- Clinical correlation, such as point tenderness directly over the growth plate, swelling, and the mechanism of injury, which can suggest a fracture even when imaging appears equivocal
- Stress views or follow-up radiographs showing healing or callus formation, which may reveal fractures initially missed on MRI
- The presence of bone bruise and adjacent soft-tissue edema, which have shown a higher association with acute ligamentous injuries and tendon abnormalities in patients with negative radiographs, as reported by Grossterlinden et al, and cited in the ACR Appropriateness Criteria 1
- The importance of accurate diagnosis, as treatment approaches differ significantly between fractures, which typically require immobilization for 3-4 weeks, and bone bruises, which may allow earlier return to activities.
From the Research
Radiologist Misdiagnosis of Salter Harris 1 Lateral Fracture on MRI
- A radiologist may misdiagnose a Salter Harris 1 lateral fracture on MRI as a bone bruise due to various factors, including interpretation differences and diagnostic errors, as discussed in 2 and 3.
- The study in 4 found that in cases where a Salter Harris 1 fracture of the distal fibula was suspected clinically, MRI evidence suggested that sprains may be more common than previously thought, and none of the patients had evidence of fibular growth plate injury on MR imaging.
- Instead, patients often had multiple abnormal findings on MRI, including ligamentous sprains, bony contusions, and subtle fibular avulsion fractures, which may be misinterpreted as a Salter Harris 1 fracture, as seen in 4.
- The characteristics of bone bruises, as described in 5, may also contribute to the misdiagnosis, as they can present with a diffuse or localized pattern of low signal intensity on T1-weighted images without a defined fracture.
Contributing Factors to Misdiagnosis
- Human- and system-derived factors, as outlined in 3, can contribute to radiologist errors, including discrepancies between radiology reports and subsequent patient outcomes.
- The study in 6 highlights the importance of strict protocols and excellent communication between the radiologist and sonographer to avoid diagnostic errors, which may also apply to MRI interpretations.
- The awareness of errors and their underlying causes, as discussed in 2, can potentially increase diagnostic performance and reduce individual harm.