SLR - May 2019 - Sharon K. Jay

MRI Diagnosis for Posttraumatic Osteomyelitis of Extremities Using Conventional Metal-Artifact Reducing Protocols: Revisited

Reference: Park B, Hong S, Yoon M, Oh J. MRI Diagnosis for Posttraumatic Osteomyelitis of Extremities Using Conventional Metal-Artifact Reducing Protocols: Revisited. Academic Radiology. 2019, January.

Scientific Literature Review

Reviewed By: Sharon K. Jay, DPM
Residency Program: The Jewish Hospital, Cincinnati, OH

Podiatric Relevance: Podiatrists often deal with potential osteomyelitis in patients who have previous ORIF or fusion and therefore retained hardware. Sometimes there is confusion if MRI is still appropriate and efficacious in these cases. This study aimed to evaluate the efficacy of utilizing Metal-Artifact Reducing (MAR) protocols on a standard 3.0T machine in identifying osteomyelitis.

Methods: This was a retrospective study collected over four years evaluating 261 consecutive patients who had MRI for possible posttraumatic osteomyelitis (PTOM). They identified 43 patients for inclusion and set against 29 controls confirmed to not have osteomyelitis by methods of biopsy or culture. Those included had symptoms consistent with osteomyelitis, such as fever or pain, and elevated ESR/CRP. All MRIs done were on a 3.0 T machine, using conventional MAR protocol. T1 Echo, both before and after contrast addition, was used, as well as T2, both with fat saturation. All films were read by two radiologists blindly, both with extensive experience in musculoskeletal MRI reading. The decision was made not to include the newest methods of reducing artifact due to lack of availability and increased cost.

Results: The term Typical Pattern referred to low signal intensity with T1, medullary distribution and confluent pattern. This finding showed high sensitivity and negative predictive value of 100 percent, as well as diagnostic accuracy of 68 percent and specificity of only 28 percent. T2 with high signal intensity, with a heterogenous distribution, also had sensitivity of 80 percent and diagnostic accuracy of 68 percent, again with specificity of only 20 percent. When these findings were combined with interosseous abscess, the specificity increased to 93 percent. A few other studies were of course referenced. One of note looked at patients with osteomyelitis and no hardware where Typical Pattern was observed, and it revealed sensitivity of 95 percent and specificity of 91 percent as well as diagnostic accuracy of 92 percent.

Conclusions: The authors concluded that while using MAR protocol reduces the sensitivity and specificity compared to use of MRI on patients without hardware, it is still the most likely method of detecting PTOM. This study was very significant because there has been the misconception that once hardware is present, the MRI will not be accurate, so it is often not ordered or the provider will opt for CT or another modality. PTOM is often a chronic lifelong condition, and it needs to be diagnosed and treated accurately and aggressively. This study gives confidence to the utilization of MRI with MAR protocol in the diagnosis of PTOM.

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