From the Guidelines
Salter-Harris type I fractures are frequently misdiagnosed on MRI due to the subtle nature of the injury and the limitations of standard MRI sequences in visualizing cartilaginous structures like the growth plate. The growth plate, or physis, is a cartilaginous region that appears as a high signal intensity line on MRI, making it challenging to detect subtle disruptions 1. Radiologists may misinterpret these injuries as normal growth plate appearance since there is no displacement or obvious bone abnormality. The diagnosis is further complicated because standard radiographs may appear normal, leading clinicians to order MRI for confirmation. However, without specific sequences optimized for cartilage visualization or without clinical correlation (such as point tenderness over the growth plate), these fractures can be overlooked.
Some key points to consider in the diagnosis of Salter-Harris type I fractures on MRI include:
- The use of in-phase and out-of-phase MRI sequences may help differentiate benign stress fractures from pathologic fractures, but this may not be directly applicable to Salter-Harris type I fractures 66.
- The edema associated with stress fractures is typically more pronounced and linear on T2-weighted sequences than on T1-weighted sequences, but this may not be sufficient to diagnose Salter-Harris type I fractures 65.
- Clinical correlation, including point tenderness over the growth plate, is crucial in making an accurate diagnosis.
- Comparison with the uninjured side, when possible, and consideration of follow-up imaging if symptoms persist despite negative initial findings, can also aid in diagnosis.
For accurate diagnosis, radiologists should prioritize clinical symptoms and correlate imaging findings with these symptoms, rather than relying solely on MRI findings 1. This approach can help reduce the risk of misdiagnosis and ensure timely and appropriate treatment for Salter-Harris type I fractures.
From the Research
Reasons for Misdiagnosis
- A Salter-Harris type I fracture is often misdiagnosed by radiologists on an MRI because the clinical presentation can be similar to other injuries, such as ligamentous sprains and bony contusions 1.
- The study by 1 found that in 18 patients with suspected Salter-Harris I fractures of the distal fibula, none had evidence of fibular growth plate injury on MRI, but instead had ligamentous sprains, bony contusions, or other abnormalities.
- The Salter-Harris classification system, which is used to classify growth plate fractures, may not be directly applicable to MRI findings, leading to potential misdiagnosis 2.
MRI Findings
- MRI may not always be able to detect Salter-Harris type I fractures, especially if the fracture is not displaced or if there is significant soft tissue swelling 1.
- In some cases, MRI may identify other abnormalities, such as ligamentous sprains, bony contusions, or subtle fractures, which can be misinterpreted as a Salter-Harris type I fracture 1, 3.
- The presence of lipohemarthrosis, which is a condition where there is blood and fat in the joint space, can also make it difficult to diagnose a Salter-Harris type I fracture on MRI 3.
Clinical Implications
- The misdiagnosis of a Salter-Harris type I fracture can have significant clinical implications, including delayed or inappropriate treatment, which can lead to long-term complications such as growth arrest or deformity 2, 1.
- A multidisciplinary approach, including physical therapy rehabilitation, is essential for managing complex knee injuries, such as those involving both growth plate and ligamentous injuries 3.