Sonography of Morton's neuromas

OBJECTIVE. The objective is to evaluate the sonographic characteristics of Morton's neuromas and the usefulness of sonography in detecting them. MATERIALS AND METHODS. Thirty intermetatarsal spaces were evaluated with so nography to diagnose Morton's neuromas. The prospective sonographic reports were correlated with surgical and pathologic findings. Each sonogram was t hen blindly and retrospectively reviewed to characterize mass echotexture, location, size, and continuity with the plantar digital nerve when present. RESULTS. Surgery revealed 27 Morton's neuromas, one synovial cyst with infa rcted tissue, one ganglion cyst, and one giant cell tumor of the tendon she ath. The prospective sonographic reports correctly identified neuromas in 8 5% of the cases. Retrospectively, 79.2% (19/24) of the neuromas were charac terized as hypoechoic compared with muscle, whereas 12.5% (3/24) were of mi xed echotexture and 8.3% (2/24) were anechoic. One half (50%) of the neurom as were located dorsal to the plantar aspect of the metatarsal heads: and 5 0% were both dorsal and plantar to this level. No statistical difference in height and width was found between neuromas and nonneuromas; however, nonn euromas were statistically greater in length than neuromas. All 15 masses i n which presumed plantar digital nerve continuity with the mass was identif ied were neuromas. CONCLUSION. Sonography can reveal a Morton's neuroma in 85% of cases. Ident ification of the presumed plantar digital nerve in continuity with the mass improves diagnostic confidence. The finding of an interdigital mass greate r than 20 mm in length should raise suspicion of an abnormality other than a neuroma.