Ainhum

Synonyms

2

Overview

Ainhum is the autoamputation of a finger or toe as a result of a fibrotic band that constricts the finger or toe until it falls off. Ainhum most often affects the fifth toe on both feet. Ainhum is believed to be triggered by some sort of trauma, but the exact reason why it happens is not well understood. The condition mainly affects people that live in tropical regions. The exact etiology is still unclear.

Symptoms

• Pain is present in about 78% of cases. Slight pain is present in the earliest stage of ainhum, caused by pressure on the underlying nerves.
• Fracture of the phalanx or chronic sepsis is accompanied with severe pain.

Causes

The true cause of ainhum remains unclear. It is not due to infection by parasites, fungi, bacteria or virus, and it is not related to injury. Walking barefoot in childhood had been linked to this disease, but ainhum also occurs in patients who have never gone barefoot. Race seems to be one of the most predisposing factors and it may has a genetic component

Prevention

Wearing shoes to protect barefoot trauma has shown decrease in incidence in ainhum. Congenital pseudoainhum cannot be prevented and can lead to serious birth defects.

Diagnosis

Histolopathology:

Histology shows a change in the prickle cell layer, and this is responsible for the laying down of condensed keratin causing the groove. The junctional tissue is reduced to a slender fibrous thread, almost avascular, and all the tissues beyond the constricting band is repressed by a fibro-fatty mass covered by hyperkeratotic integument.

Imaging:
Soft tissue constriction on the medial aspect of the fifth toe is the most frequently presented radiological sign in the early stages. Distal swelling of the toe is considered to be a feature of the disease. In grade III lesions osteolysis is seen in the region of the proximal interphalangeal joint with a characteristic tapering effect. Dispersal of the head of the proximal phalanx is frequently seen. Finally, after autoamputation, the base of the proximal phalanx remains. Radiological examination allows early diagnosis and staging of ainhum. Early diagnosis is crucial to prevent amputation. Doppler shows decreased blood flow in posterior tibial artery.

Differential diagnosis:
Ainhum is an acquired and progressive condition, and thus differs from congenital annular constrictions. Ainhum has been much confused with similar constrictions caused by other diseases such as leprosy, diabetic gangrene, syringomyelia, scleroderma or Vohwinkel syndrome. In this case, it is called pseudo-ainhum, treatable with minor surgery or intralesional corticosteroids, as with ainhum. It has even been seen in psoriasis or it is acquired by the wrapping toes, penis or nipple with hairs, threads or fibers. Oral retinoids, such as tretinoin, and antifibrotic agents like tranilast have been tested for pseudo-ainhum. Impending amputation in Vohwinkel syndrome can sometimes be aborted by therapy with oral etretinate. It is rarely seen in the United States but often discussed in the international medical literature. 

Treatment

Incisions across the groove turned out to be ineffective. Excision of the groove followed by z-plasty could relieve pain and prevent autoamputation in Grade I and Grade II lesions. Grade III lesions are treated with disarticulating the metatarsophalangeal joint. This also relieves pain, and all patients have a useful and stable foot

Resources

• NIH