Review Question - QID 218904

A 47-year-old food truck vendor presents to the emergency room after cutting the distal tip of his ring finger off with a meat cleaver. On exam, there is an exposed distal phalanx and less than 1 cm of residual nail plate intact. When performing a revision amputation procedure at the bedside, the residual nail plate is removed and a rongeur is used to take back the exposed bone until adequate soft tissue coverage is achieved. The patient returns to the clinic unhappy, explaining that his nail has regrown with a large split down the middle (Figure A). What structure was most likely damaged to result in this type of nail deformity?