[Reconstruction of thumb length by "on-top plasty"].

We report the case of a 23 year old man who suffered amputation of thumb and index finger at the metacarpophalangeal joint by an injury with electrical current. In order to elongate the first ray an on-top plasty of the second on the first metacarpal bone was performed. The second metacarpal was severed above the base and with the intact vessels and the first dorsal interosseous muscle placed on the distal end of the first metacarpal. The second dorsal interosseous muscle was severed. The first and second metacarpal bones united with an intramedullary cortical inlay graft. Nerve and vessels as well as the skin of the back of the hand could be moved without tension. An abdominal tube was applied to the palm because of severe scarring. As a final result pinch grip between the thumb ray and the rest fingers is possible. The other fingers are freely movable.