Fig. 37.3 Ainhum showing spindling and atrophy of the bone in the area of the constriction in this bisected surgical specimen from the same patient as in Fig. 37.2. X l.3. AFIP 75-10758. (From C.H. Binford and D.H. Connor, eds. Pathology of Tropical and Extraordinary Diseases. Armed Forces Institute of Pathology, Washington DC, 1976).

Fig. 37.4 (A) Specimen radiograph of surgically amputated toe from same patient as in Figs. 37.2 and 37.3. Note resorption of the outer cortical layers with resultant narrowing of the phalanges. The vertical line is an artifact since the toe had been bisected and the halves reopposed for radiography. AFIP 76-6316. (From C.H. Binford and D.H. Connor, eds. Pathology of Ttropical and Extraordinary Diseases. Armed Forces Institute of Pathology, Washington DC, 1976) (B) Section of a toe in ainhum from another patient, showing atrophy and disappearance of the phalanx, as well as marked soft tissue fibrosis, at the level of constriction. X2. (From Spencer and Hutt 1973).

Fig. 37.5 A Fifth toe amputated because of ainhum reveals an area of ischemic ulceration as well as a prominent constricting groove encircling the toe at the digital plantar fold. (From Rose 1995) B Ainhum showing fibrosis of the dermis and deeper tissues and almost complete atrophy of the underlying bone in the area of the constriction. AFIP N-82250. (From C.H. Binford and D.H. Connor, eds. Pathology of Tropical and Extraordinary Diseases. Armed Forces Institute of Pathology, Washington DC, 1976).

 

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Etiology and Pathology

In its later stages, there is hyperkeratosis within the epidermis and chronic inflammatory changes and fibrosis in the tissues underlying the ulceration. Presumably the ulceration develops as a consequence of infection and maceration of tissue deep in the groove, where the skin surfaces are constantly in contact with one another. A 1986 report by Kerhisnik et al described certain scanning electron microscopic and histochemical findings, including hyperkeratosis and parakeratosis, associated with elongation of the epidermal rete ridges and acanthosis, as well as the presence of numerous fibroblasts and wound repair phenomena. A leukocytic infiltrate predominantly of T lymphocyte type raises the possibility of an unknown immunologic response. A 1988 histopathological study of 7 patients by Warter et al. revealed complete ligamentous destruction in all cases and vegetal foreign body granulomas deep in the dermis in 4 patients.

The tissues encircled by the groove are gradually compressed; tendons, ligaments, and joint capsules become atrophic and eventually are replaced by dense fibrous tissue. The bone adjacent to the groove becomes thinned and tapered from pressure absorption of the outer layers of the cortex (Figs. 37.3, 37.4, 37.5). Pathological fracture of the underlying phalanx may occur. Marked angulation at the constriction site is common, with severe bony changes. Often a painful soft tissue swelling or "bulb" occurs distal to the constricting fissure as a result of lymphedema and venous obstruction; an ischemic soft tissue ulceration can develop (Fig. 37.5). Eventually spontaneous amputation of the toe may result. The entire process from beginning to end may take from 3 months to more than 20 years, with an average duration of 5 years.

To summarize, four stages in the development of ainhum are recognized:

1. A groove.

2. A groove with ulceration

3. Underlying bone involvement.

4. Auto-amputation.

The digit most commonly affected is the fifth toe, although the second, third and fourth toes may also be involved either concomitantly or alone. The condition is frequently bilateral. Rarely, the fingers may be involved in a manner similar to the toes.

Laboratory Diagnosis

There are no specific laboratory tests; there is no familial incidence. There are no serological, hematological or biochemical tests. The diagnosis is entirely clinical and may be confirmed radiologically.

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