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Clinical Characteristics

Ainhum is a relatively common affliction of blacks of both sexes and all ages between 6 and 75, with a special predilection for middle-aged males in their fourth and fifth decades living in the African tropics. The typical patient has walked barefoot for much or all of his life or has worn primitive shoes. The site of involvement is almost always the fifth toe and is often bilateral (in up to 75% of patients), but other toes may occasionally be involved, and rarely a finger. Pain in the affected digit can occur in stage 1 and is almost always present in stages 2 through 4. Pain is especially pronounced after a pathological fracture and is usually the presenting symptom causing the patient to seek medical attention. Patients who develop a "bulb" or marked lymphedematous swelling of the toe distal to the groove often have considerable pain. If the process has been present for a long time there may be edema of the dorsum of the foot, probably on the basis of chronic infection around the base of the involved toe. Ainhum is often associated with pallor of the affected digits, hyperkeratosis of the skin, and deformity of the nails.

Abduction and hyperextension deformity of the toe, with loss of voluntary movement, may follow marked underlying bone involvement. If a fracture has occurred, there may by 90° abduction of the toe with external rotation and marked hyperextension (flail toe). Outward rotation of the involved toe has been ascribed to late ainhum, but it should be remembered that dissection of amputated toes has shown no rotation of the bones or change of axial movement at the joints. Furthermore, the little toes not infrequently have the nail facing outward by as much as 60°, which may give an erroneous impression of rotation of the toe.

The end result of untreated ainhum is often auto-amputation of the toe, with the stump of the proximal phalanx remaining intact together with its metatarsophalangeal joint. Surgical amputation may be required in the later stages of ainhum when pain persists, even after auto-amputation, because the remnant of the proximal phalanx sometimes protrudes through the skin and causes ulceration. It is well to remember that ainhum usually occurs in otherwise healthy individuals, and what appears to be a trivial lesion often causes prolonged and, at times, severe crippling disability. It is fortunately curable by appropriate surgery. Complex investigations and laboratory tests searching for some other disease to explain the etiology of ainhum are unwarranted.

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Copyright: Palmer and Reeder

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