Risk factors and the associated cutoff values for failure of corticosteroid injection in treatment of Morton’s neuroma

Background: Understanding the risk factors that predict the prognosis of Morton’s neuroma after corticosteroid injection would help clinicians determine the appropriate treatment protocol. However, the cut-off values for the risk factors are unknown. The aim of this study was to identify the risk factors and cut-off values that predict failure of corticosteroid injection in treatment of Morton’s neuroma. Method: Among 201 patients who had corticosteroid injection for Morton’s neuroma, 40 underwent further treatment after injections. Injection was performed with ultrasound guidance following ultrasound confirmation of the diagnosis. We compared demographic information, size of the neuroma, and other comorbidities between the patients who did and did not undergo further treatment after injection in order to determine the risk factors of failure. Receiver operating characteristic (ROC) curves were constructed to determine optimal cutoff values for each risk factor. Results: Stepwise logistic regression analysis showed that larger neuromas (p < 0.001) and younger patients (p = 0.026) predicted the failure of corticosteroid injection. The optimal cutoff value for the size of the neuroma was 6.3 mm (sensitivity, 81%; specificity, 95%; positive predictive value, 84%; negative predictive value, 88%) for predicting the failure of corticosteroid injection. Age was not associated with a specific cutoff value. Conclusions: This study found that, with a cut-off value of 6.3 mm, larger Morton’s neuromas were associated with failure of corticosteroid injection.