These are injuries due to the disruption of the blood vessels of the nail bed. The area of the hematoma is directly proportional to the degree of vascular damage. If the hematoma covers less than 50 percent of the area beneath the nail, treatment can be accomplished with trephination of the nail plate to allow for adequate decompression and drainage of the hematoma. Various tools have been used effectively for this purpose, including a heated paper clip, electric nail drill, electrocautery, 18-gauge needle, and scalpel. The disadvantages with the heated paper clip include coagulation of the hematoma and introduction of carbon particles called "lampblack" into the nail bed, which may delay healing.8 Use of a needle, scalpel, or nail drill can be painful and may necessitate local anesthesia. A hand-held electrocautery device permits rapid and painless trephination and is sterile and disposable. 8 However, not every ED will be equipped with such a tool, and emergency physicians will likely perform nail trephination using tools they are familiar with. Patients are discharged with local wound care instructions to soak the affected finger in warm water containing antibacterial soap two to three times a day for 7 days.
It is commonly recommended that for a subungual hematoma occupying more than 50 percent of the nail bed area, the nail be removed in order to evaluate the nail bed and repair any associated laceration. 258 However, there are two prospective studies which found that simple trephining produces a good to excellent outcome in about 85 percent of patients with subungual hematoma regardless of its size, the presence of fracture, or infection. 910 Therefore, simple trephination is an adequate treatment for most simple subungual hematomas, with nail removal recommended if there is associated nail avulsion or surrounding nail fold disruption.
Nail removal can be accomplished with adequate anesthesia, digit exsanguination, nail elevation using a small hemostat, elevation of the eponychium off the nail, and then removal by gentle longitudinal traction with a hemostat. Lacerations of the nail bed are carefully repaired using 7-0 absorbable sutures. Crush injuries often result in stellate lacerations, which may require extensive meticulous repair with a magnification loupe. The nail is gently cleaned with saline, taking care not to damage the germinal matrix; it is then trephinated and secured in its anatomic position. This is accomplished by placing a 5-0 nylon suture through the distal end of the nail plate and then passing it underneath and through the center of the eponychial fold. Once the nail plate is returned to its anatomic position, the suture is tied down over the nail. The replaced nail acts as a natural splint to the terminal phalanx, prevents formation of synechiae, and protects the sensitive nail bed. If the nail is not available, nonbiological stents made of Silastic (Dow Corning) or silicone may be used to elevate the eponychium and protect the nail bed. Similarly, a sterile piece of aluminum foil used to wrap suture materials may be fashioned into the dimension of the avulsed nail and inserted under the eponychium. The fingertip is then dressed in nonadherent gauze and placed in a volar splint to limit movement at the DIP joint. Patients are given postoperative wound care instructions (e.g., as to hand elevation) as well as neurovascular checks and given adequate pain relief. Unless obvious purulence is noted, the dressing is left undisturbed for 5 to 7 days after which the site is examined for new hematoma formation. The suture attached to the nail is removed after 3 weeks; the existing nail will be dislodged by the new ingrowing nail after 1 to 3 months.
If an associated distal phalanx fracture coexists with a nail bed laceration, it usually manifests as an avulsion of the nail out of the proximal eponychial fold. If this happens, the nail is removed, the fracture is stabilized by manual reduction, and the nail bed is repaired as previously described. The nail replaced in its anatomic position serves as a biological splint to maintain fracture reduction, owing to its proximity to the underlying bone. Unstable reductions require consultation with a plastic or hand surgeon for internal fixation using Kirschner wires to prevent deformity of the nail bed.
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