Ultrasound Shear-Wave and Strain Elastography for Differentiating Morton's Neuroma from Intermetatarsal Bursitis

Background: Ultrasound (US) is a well-established imaging modality for the diagnosis of Morton's neuroma (MN), although differentiating MN from intermetatarsal bursitis (IMB) may be challenging in some cases. US elastography, including strain elastography (SE) and shear wave elastography (SWE), enables the assessment of tissue stiffness. Because MN is predominantly composed of fibrotic tissue whereas IMB contains fluid, we hypothesized that elastography could improve the differentiation between these two conditions. Methods: Fifty consecutive patients (43 women) with clinically suspected MN involving 71 feet were prospectively enrolled. All patients underwent both US and MRI, independently interpreted by two radiologists. Patients with imaging findings suspicious for MN on either modality underwent surgery, with histopathology serving as the reference standard. Cases not meeting surgical criteria were classified as IMB based on imaging and clinical follow-up. During US examination, SE and SWE were performed. The Strain Ratio (SR), SWE lesion stiffness, subcutaneous tissue stiffness, and the SWE lesion-to-subcutaneous tissue stiffness ratio (hereafter, SWE ratio) were recorded. Elastographic parameters were compared between MN and IMB, and their diagnostic performance was evaluated using receiver operating characteristic (ROC) curve analysis. Results: MN demonstrated significantly higher SR and SWE stiffness than IMB. The SWE ratio achieved the highest diagnostic performance, with an AUC significantly greater than those of SWE lesion stiffness (0.915 vs. 0.718, p = 0.004) and SR (0.915 vs. 0.719, p = 0.002). Using a cut-off value >1.5, the SWE ratio yielded 79.2% sensitivity, 88.9% specificity, and 81.7% overall accuracy. Conclusions: US elastography, particularly the SWE ratio, may represent a valuable adjunct to conventional US for differentiating MN from IMB, improving the diagnostic performance of US.