Causes / typical injury mechanism: Fingertip and thumb tip injuries are among the most common traumatic injuries that present in acute care settings. Lacerations, crush injuries, and avulsions are the most common mechanisms, resulting in a spectrum of injuries from
subungual hematomas to complete tip amputations.
Prevalence:
- Age – While these injuries can occur across all age ranges, they are more prevalent in young children.
- Sex / gender – There is a slight predilection toward males.
Pathophysiology: Firm knowledge of fingertip anatomy is critical to proper management. The distal phalanx provides bony support for the tip and serves as the terminal insertion for the extensor apparatus and flexor digitorum profundus tendon (or flexor pollicis longus in the thumb). The nail plate and nail bed are adherent to each other and to the periosteum of the distal phalanx below. The soft tissue surrounding the nail is referred to as the perionychium. The eponychium, or cuticle, is the portion of the perionychium that lies proximal to the nail. The nail bed itself is also part of the perionychium and is composed of the sterile matrix distally, which makes up a majority of the bed, and the germinal matrix, which can be visualized as the lunula (ie, white portion of the proximal nail) and continues proximally under the eponychium. The sterile matrix is responsible for nail adherence, while the geminal matrix is responsible for 90% of actual nail growth. Finally, the volar pulp constitutes more than half of fingertip volume and is integral to grip, proprioception, and sensation.
Grade / classification system: Numerous classifications to describe tip injuries and amputations exist. Some schemas classify injuries based upon injury geometry (ie, volar versus dorsal oblique injuries, with or without bone involvement), while others focus on the location of injury. One simple descriptive framework for tip amputations is to divide the fingertip into zone I (distal fingertip to lunula) and zone II (lunula to distal interphalangeal joint). However, a thorough description of the injury, including mechanism, location, geometry, and structures involved, can ultimately obviate the need for classification.
