Anesthetic Suppression Test to Differentiate Morton’s Neuroma from Mechanical Metatarsalgia: A New Diagnostic Tool?
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Background and Objectives: The anesthetic nerve block test is a surgical technique that can assist in the differential diagnosis of forefoot pain, particularly in cases where clinical presentation is complex and diagnostic uncertainty is common. So, the aim of this study was to propose an alternative to the current procedure, which is known to produce a high rate of false positives in suspected cases of Morton’s neuroma. Material and methods: An experimental anatomical study was conducted on six fresh cadaveric feet. Under ultrasound guidance, the second, third, and fourth metatarsophalangeal joints were infiltrated with progressively increasing volumes of radiopaque contrast medium. Additionally, the third common digital nerve was injected in a healthy segment of the nerve within the third intermetatarsal space. Standard radiographs were then obtained to evaluate the distribution and proximal spread of the injected fluid. Results: A volume of 0.3 ml was sufficient to fully reach the intra-articular cavity and induce effective localized anesthesia. When the third common digital plantar nerve was injected in an anatomically healthy region, the contrast medium showed a proximal diffusion pattern extending up to the mid-diaphyseal level of the third and fourth metatarsal bones. Conclusions: Low intra-articular volumes of anesthetic may be sufficient to achieve a targeted clinical response, whereas injection into a Morton’s neuroma leads to a broader proximal spread, potentially anesthetizing adjacent anatomical structures and thus reducing diagnostic specificity. This refined technique may enhance the accuracy of therapeutic decision-making and reduce treatment failures in patients with suspected Morton’s neuroma.