MORTON NEUROMA AND FLUID IN THE INTERMETATARSAL BURSAE ON MR-IMAGES OF 70 ASYMPTOMATIC VOLUNTEERS

PURPOSE: To determine the prevalence and size of presumed Morton neuro mas and fluid in the intermetatarsal bursae on magnetic resonance (MR) images. MATERIALS AND METHODS: In 70 asymptomatic subjects, transaxia l T1-weighted spin-echo and T2-weighted turbo spin-echo images were ob tained of the right forefoot. The prevalence and size of presumed Mort on neuromas (diagnosed with MR imaging criteria) were evaluated, and t he sizes were compared with those of 16 symptomatic, surgically proved Morton neuromas. The prevalence and diameter of fluid collections in the intermetatarsal bursae were evaluated on the T2-weighted images. R ESULTS: Twenty-four Morton neuromas were diagnosed in 21 subjects (pre valence, 30%). The transverse diameter of the neuromas was 3-7 mm (mea n, 4.5 mm) versus 4-8 mm (mean, 5.6 mm) in symptomatic subjects; this difference was significant (P = .0075). The prevalence of fluid in the intermetatarsal bursa was 20%, 47%, 49%, and 0% for the first through fourth intermetatarsal spaces. The transverse diameter of the fluid c ollection was 1-4 mm. CONCLUSION The diagnosis of Morton neuroma at MR imaging may be relevant only when the transverse diameter is 5 mm or more and can be correlated to clinical findings. Fluid collections in the first three intermetatarsal bursae with a transverse diameter of 3 mm or less can be considered physiologic.