Posttraumatic ectopic nail: a usual manifestation and treatment of an unusual anomaly.

Dear Editor:

Ectopic nail is defined as the development of nail tissue in a location other than the usual nail unit. More than 50 cases have been reported, and most are congenital1. We present the case of a 21-year-old man with traumatic ectopic nail. He had two horny prominences on the dorsal area of the distal phalanx on the third finger (Fig. 1) that had been present for approximately 6 years. He had a history of fingertip injury treated surgically. On dermatological examination, nail-like structures 3×5 mm and 5×10 mm were noted, and the surrounding skin was slightly swollen without inflammation. Other nails were unaffected. There was no pain, discomfort, or joint movement limitation. Radiographic evaluation revealed no bone deformity.

Fig. 1

(A) Close-up view of the ectopic nail showing a bipartite structure. The root of the detached nail located on the distal phalanx extending through the proximal nail fold (PNF). (B) Both parts are separated with longitudinal incision and oblique incisions were made at the both corners of PNF. Care should be taken not to damage main matrix and insertion of tendon. (C) No recurrences or nail deformity 1 year after the treatment.

After digital block with lidocaine, we applied a tourniquet to avoid bleeding. To preserve the matrix of the normal nail and minimize the risk of recurrence due to incomplete excision of the ectopic matrix, we exposed the whole surgical area. Oblique incisions were made at both corners of the proximal nail fold (PNF). After inserting the scalpel just beneath the ectopic nail to its base, we undermined the ectopic matrix and exposed the normal nail matrix. The ectopic nails were completely excised with their matrices, keeping away from the main nail unit to avoid permanent nail dystrophy. Finally, primary sutures were placed. The histopathology of the excised material was similar to the normal nail plate and matrix. There has been no recurrence or nail disfigurement after 1 year.

Various hypotheses proposed about the genesis of ectopic nail include the presence of stray germinal cells, persistence of a rudimentary nail after polydactyly regression, traumatic inoculation of onychocytes, and the role of onychodermis in nail plate formation1,2,3,4. Most of the reported posttraumatic cases showed dorsal finger predominance3. Their clinical manifestations and the history of trauma verify the idea of inoculation of nail matrix in fingernails. Our case is consistent with the acquired forms reported in the English literature (12 cases). Among them, seven cases were declared posttraumatic, and all involved the dorsal aspect of the fingers and toes. Although the remaining five cases were not associated with trauma, analysis of their location suggested a probable traumatic etiology. However, traumatic inoculation is insufficient to explain the congenital, and some acquired, cases. Regardless of type (congenital or acquired), the treatment for ectopic nail is total excision including the matrix. Incomplete excisions can result in recurrences1,2,5. Our case demonstrates the inoculation of nail matrix in the dorsal finger. In traumatic forms affecting the fingertips, the detached matrix is generally transferred to dorsal areas closely related to the main matrix. During surgery for such cases, the proximity of both main and detached matrix is important to prevent recurrence and the disfigurement of the main nail. Another potential complication related to the dorsal location is disruption of extensor tendon insertion. In conclusion, adequate exposure of the surgical area is crucial, and oblique incisions made at the corners of the PNF are appropriate for traumatic ectopic nails.