Interdigital, or Morton’s neuromas are a common cause of lesser metatarsalgia, or pain that arises from the 2nd through 5th MTP joints and surrounding soft tissues. Ultrasound is an excellent modality for the rapid diagnosis of interdigital neuromas and allows direct correlation of imaging findings with sonopalpatory pain.
When evaluating for an interdigital neuroma, I routinely image the metatarsal interspace from both the dorsal and plantar approaches. Each approach has distinct advantages and limitations, and proficiency with both techniques is essential for a comprehensive assessment of the interspace. From the dorsal approach, I apply thumb pressure along the plantar aspect of the interspace to displace the interdigital nerve and intermetatarsal bursa dorsally, often resulting in a more conspicuous appearance. In the following video, I demonstrate the appearance of an interdigital neuroma from both the dorsal and plantar approaches. Additionally, an injection into the neuroma nicely delineates the interdigital nerve from the surrounding bursal tissue.
A thorough evaluation of the metatarsal interspace requires imaging from both the dorsal and plantar approaches. A detailed review of the forefoot anatomy, sonoanatomy, live scan techniques, and pathology — including interdigital neuromas — is provided in the Forefoot Module.