Morton's intermetatarsal neuroma: morphology and histological substrate.

Twenty-three biopsies from patients with the typical symptoms of intermetatarsal neuroma (so-called Morton's metatarsalgia) were compared histologically and semi-quantitatively with 25 plantar nerves from the intermetatarsal space III/IV gained at autopsies from cases where no problems in the forefoot had been recorded. The histomorphological examination of the nerves from autopsies revealed the same findings as were found in the biopsies. Thus, qualitatively, the nerves from patients could not be distinguished from those gained at autopsy. The only difference was the diameter of the resected nerves: semi-quantitative analysis of the nerves showed that the 17 thinnest ones were all from autopsies and the five thickest ones from biopsies of symptomatic patients. At medium diameters, however, there was wide overlap of the two groups. The study yielded a specificity of the swelling of 80 % and a sensitivity of 78%. From these results it must be concluded that diagnostic MRIs or ultrasonography, are unnecessary for decision-making about operative treatment and are not superior to exploratory local anaesthesia. Since histomorphological findings in intermetatarsal neuroma (so far accepted as the gold standard for confirmation of that diagnosis) were the same as findings in autopsied (normal) specimens, the value of postoperative histological examination is questioned. It merely proved that the nerve has been resected.