The role of fasciae in the pathogenesisi of Civinini-Morton Syndrome

Background: The aim of this study was to investigate the role of foot fasciae and of the connective tissue sheath of the intermetatarsal plantar nerves (IPN) in the pathogenesis and clinical presentation of Civinini-Morton’s metatarsalgia. Materials and methods: ten not-embalmed feet were dissected in order to analyze the relationships of the IPN with the deep transverse metatarsal ligament (DTML) and with the fasciae of the foot. For each foot, samples of the nerve with all surrounding connective tissue were taken for hystological analysis. Finally, 30 MRI and 10 dynamic US were used to evaluate the aspect of the perineural connective tissue in patients with Civini-Morton’s syndrome and healthly people. Results: The data confirms that the bifurcation of the common digital nerve of the foot in the second and third webspace is always distal to the DTML. Around the nerve, concentric layers of fibrous and loose connective tissue create a protection for the nerve. This arrangement of the perineural tissue may be compared to a "telescope" and may allow compliance between nerve and foot during walking. In patients, the perineural connective tissue appears altered; in particular, it first shows perineural edema, followed by hyalinization and sclerosis. Perineural vessels undergo gradual sclerosis. Cell proliferation, with the appearance of neuroma, is only the last step. Discussion: Clinically, a thickening of fibrosis of the perineural connective tissue could decrease this "sliding system," exposing the nerve to mechanical effects of load during walking and causing the symptoms.