Ainhum and Pseudoainhum Are Syndromes Related to External Constricting Bands
- Constricting bands are classified as ainhum and pseudoainhum.
- Ainhum is defined by a constricting band around a digit and is most common in tropic and subtropic latitudes occurring around the fifth toe or toes of people accustomed to walking barefoot.
- Pseudoainhum constrictions clinically mimic ainhum and are much more common in the developed world. It may be caused by (1) amniotic bands; (2) constrictions associated with keratotic disorders or those associated with infections or trauma; and (3) constriction by external forces such as hairs and threads.
- Autoamputation can result from ainhum and pseudoainhum.
- Treatment can simply be the removal of foreign strands wrapped around a digit or limb or surgical intervention in more advanced cases (Z-plasty or amputation).
Constricting bands are classified as ainhum and pseudoainhum. Ainhum describes the development of constricting bands around toes in underdeveloped countries of Africa and may ultimately result in autoamputation. In the African Yorub language, ainhum means “to saw” or “file” and in the Brazilian patois, it means “fissure.” In the remainder of the world, constricting bands that mimic ainhum are termed pseudoainhum.
Ainhum (dactylolysis spontanea) is traditionally a disease of middle-aged African males accustomed to going barefoot.1 In the tropic and subtropic climates, its incidence has been reported as between 0.015% and 2% of the population.2 This same condition is rarely seen throughout the rest of the world. Occasional isolated cases were reported in the United Kingdom and North America.1,3 Pseudoainhum of all types is very rare.
The pathogenesis of ainhum has not been clearly elucidated. Chronic trauma, infection, hyperkeratosis, decreased vascular supply, and impaired sensation may produce excessive fibroplasia in a susceptible host.4 Dent et al described impaired blood supply to the foot proximal to the groove at the plantar digital junction. Poor perfusion was the result of attenuation of the posterior tibial artery and absence of the plantar arterial arch leading to abnormal healing following mechanical trauma. Ainhum has also been blamed on rotational stress applied to the bare, mechanically unstable foot.5
There are three pathophysiological categories of pseudoainhum: (1) congenital constricting bands are caused by the umbilical cord; (2) constriction by external forces, such as hairs or threads, which are generally factitial; and (3) constricting bands secondary to other diseases. These may be hereditary or nonhereditary. Hereditary causes include pachyonychia congenita, Mal de Meleda, mutilating keratoderma,6 lamellar ichthyosis,7 and psoriasis.8–10 Nonhereditary diseases include vascular anomalies as seen in Raynaud disease, diabetes mellitus, linear scleroderma, systemic sclerosis. Sensory changes associated with leprosy, tertiary syphilis, syringomyelia, and spinal cord tumors as well as trauma resulting in scar formation from burns, frostbite, and physical trauma can also cause constricting bands to form. When associated with chronic trauma and infection of the extremities, the pathophysiology may be identical to true ainhum.