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This companion article to interdigital perineural fibroma (a.k.a. Morton's neuroma [MN]) discusses the anatomy and physiology of the nerves in the forefoot, clinical presentation, diagnosis, and treatment of this painful fore foot condition. Although no empirical causal data exists to associate MN with Morton's syndrome or Morton's toe, a condition has been described in the literature whereby particular foot architecture has been linked to anomalies in the first and second metatarsals. This alteration in forefoot structure creates changes in foot biomechanics, precipitates foot pain, and alters foot functioning. To juxtapose this article with the possibility of Morton's syndrome, a family vignette referred to as "Jane's Genus" will be provided as an example of the prevalence of Morton's toe in one family.
Primary changes in form and function are followed by determinable changes in the outer shape and the inner architecture of the involved bone.
Weinmann & Sicher 1955, p. 174
Normal bipedal locomotion causes varying biomechanical stresses and strains on the feet. Ill-fitting shoes, repetitive movements, and everyday walking can affect soft tissue and osseous structures.
Minor alterations in foot biomechanics may, after many years, bring about chronic changes to foot structures precipitating painful foot syndromes and conditions such as Morton's neuroma (MN).
The literature has discussed a phenomenon called Morton's syndrome or Morton's toe. Morton's syndrome is a triad associated with a short first metatarsal segment, a long second metatarsal phalangeal joint, and hypermobile first metatarsophalangeal (MTP) segment with associated posteriorly placed sesamoids ossicles (see Figure 1).
Epidemiology
Interdigital perineural fibroma or Morton's neuroma is a painful benign mechanical entrapment neuropathy affecting a common digital nerve in the forefoot (Wu, 1996) (see Figure 2). The predominance of female to male ratio for this condition is 5:1, and the third interspace in the foot is the most common region affected. Multiple neuromata may be present in the same foot, as well as, bilateral foot involvement (Mollica, 1997). Daily activities requiring persistent and excessive squatting, sports, and vocations requiring forced dorsiflexion of the toes are precipitating factors.
Nerve Innervations in the Foot
The sensory cutaneous and muscular nerve innervation to the ankle and foot is derived from the femoral and sciatic nerves and their major branches. One branch includes the saphenous nerve. The saphenous nerve...