Trauma to the nail unit including occupational sports injuries.

Trauma to the nail unit is one of the most common causes of onychodystrophy and may be acute (a single overwhelming injury) or chronic (repeated minor injury). Immediate effects of acute trauma include splinter hemorrhages, subungual hematomas, and nail shedding. Delayed deformities include splits and ridges, pterygium, hook nails, pigment bands, and ectopic nail. Also discussed are the results of chronic trauma, including self-inflicted injury and repeated indirect injury.