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Adhering to certain principles will improve the outcome when repairing nail beds. A smooth and flat nail bed is necessary to the normal growth of the nail and should be the primary goal in any repair. Avoid or severely limit the amount of debridement.5 The germinal matrix must be meticulously repaired and the proximal nail fold, the eponychium, preserved or that space is obliterated within a few days and result in adhesions or abnormal nail growth.5 Thoroughly clean and replace the nail plate whenever possible. This will preserve the nail folds surrounding the nail bed, allow the nail plate to serve as a splint for fractures, and act as a protective cover for the healing nail bed.6 Treatment goals also include preservation of length and sensation of the fingertip, early mobilization, prevention of joint contractures, and attention to cosmesis.4,17
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The technique of nail bed repair depends upon the type of injury as well as which structures are involved. Various classification schemes, such as the nature of injury or anatomic location, have been developed to categorize fingertip injuries and guide treatment. Nail bed injuries are classified as simple lacerations, crushing lacerations, avulsion-lacerations, lacerations with associated fractures, lacerations with loss of skin and pulp, and fingertip amputations.2,12
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A significant force is required to break the nail plate. The nail plate should be removed to visualize the underlying nail bed if the nail plate is damaged or avulsed, or the lateral skin folds lacerated as an associated nail bed injury is highly likely. Removal of the nail plate is unnecessary in minor injuries where the nail plate is not damaged and still attached to the nail folds.
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Remove the nail plate to repair nail bed injuries or to inspect the nail bed for potential injuries (Figure 104-7). Insert the closed tips of a fine scissors between the nail bed and the nail plate. A periosteal elevator, if available, can be substituted for the scissors. Hold the scissors parallel to the long axis of the finger. Slightly angle the tips of the scissors toward the nail plate to prevent any damage to the nail bed.11 Advance the tips of the scissors 1 to 2 mm. Open the blades of the scissors to separate the nail bed from the nail plate. Close the blades of the scissors. Continue to advance the tips of the scissors in 1 to 2 mm increments and separate the nail bed from the nail plate. Stop advancing the scissors when the tips of the blades are at the level of the eponychium. Firmly grasp the nail plate with a hemostat. Pull the nail plate parallel to the long axis of the finger to completely remove it from the finger.
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Making two linear incisions with a scalpel at 90° from the eponychial edge will allow greater exposure to the germinal matrix for repair (Figure 104-8).7 This allows the eponychium to be folded or sutured back and therefore increase exposure of the germinal matrix.2,17
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Simple lacerations are caused by localized blows to the nail plate. After removing the nail plate and exposing the nail bed, repair the laceration meticulously using 6-0 or 7-0 chromic gut or irradiated polyglactin 910 sutures.2,6,17 Minimize debridement as much as possible to avoid scarring that will result in nonadherence or splitting of the nail plate. Repair any skin lacerations adjacent to the nail bed using 6-0 or 5-0 monofilament nylon sutures.5 Nail fold lacerations may require repair in layers in order to preserve these spaces.9
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The second type of injury is a crush injury with resultant lacerations. Crushing injuries may produce stellate lacerations and fragmentation of the nail bed (Figure 104-9A). Attempt to meticulously repair the fragmented nail bed using 6-0 or 7-0 chromic gut or irradiated polyglactin 910 sutures to achieve precise approximation and the smoothest result possible (Figure 104-9B).6
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The third type of nail bed injury is the avulsion-laceration (Figure 104-10A). These injuries are more complex than the previously described injuries. Distal nail bed avulsions simply require petrolatum gauze to be placed over the injury followed by sterile gauze. Suture the petrolatum gauze and sterile gauze in place using 5-0 or 6-0 nylon suture for 10 days to allow the wound to heal by second intention (Figure 104-10B).5,17 Avulsion-laceration injuries may require consultation with a Hand Surgeon depending on the amount of tissue involved and whether the germinal matrix is involved.6,11,12 More severely damaged nail beds with a large amount of avulsed tissue usually require dermal grafts or split-thickness matrix grafts.6
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Small fragments of avulsed nail bed may remain attached to the nail plate. These may be simply treated by carefully replacing the nail plate in its anatomic position.18 Larger segments of avulsed nail bed that remain attached to the nail plate should be repaired (Figures 104-11A & B). Gently shave away the nail bed from the nail plate with a #15 scalpel blade (Figure 104-11C). Replace the avulsed nail bed and suture it in place with 5-0 or 6-0 chromic gut or irradiated polyglactin 910 sutures (Figure 104-11D).10,18 Apply a petrolatum gauze dressing and replace the nail plate.
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A special type of avulsion injury occurs when there is a crush injury to the distal fingernail. This results in an avulsion of the proximal nail plate with or without involvement of the germinal matrix (Figure 104-2). The proximal nail plate is less adherent to the nail bed and can be pulled out from under the eponychium (Figure 104-2). Remove the nail plate if the proximal nail plate is avulsed without involvement of the germinal matrix. Clean the nail plate and nail bed with sterile saline. Replace and secure the nail plate.
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More often with these crush injuries the germinal matrix is avulsed as well. In these cases, the germinal matrix should be replaced with a series, usually three, of 6-0 nylon simple interrupted or horizontal mattress sutures (Figure 104-12).5,6,10 Place all three sutures before returning the nail bed to its proper location. Making two linear incisions with a scalpel at 90° from the eponychial edge will allow exposure to the germinal matrix for repair (Figure 104-8).7 This allows the eponychium to be folded or sutured back and therefore increase exposure of the germinal matrix. Place a piece of petrolatum gauze between the eponychium and the germinal matrix after the repair (Figure 104-12B). Larger germinal matrix avulsions require consultation with a Hand Surgeon for grafting.2,6,11,17
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Lacerations with Associated Fractures
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The fourth type of nail bed injury is lacerations associated with fracture(s). Approximately 50% of nail bed injuries have an associated phalangeal tuft fracture.19 The nail bed laceration should be repaired as previously described and the fracture addressed as a separate entity.5 It is important to remember that the sterile matrix is closely adherent to the dorsal periosteum of the distal phalanx. Therefore, fractures require precise anatomic reduction in order for normal nail bed healing and nail plate growth to take place.6,10,12 Replacing the nail plate and splinting the finger after repairing the nail bed laceration is often enough to reduce these fractures. Occasionally, fixation may be employed by a Hand Surgeon using Kirschner wires to prevent rotation of the bony fragments.2,6
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Lacerations with Skin Loss and Fingertip Amputations
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The final two types of injury are lacerations with loss of skin and pulp, and fingertip amputations. They can be further classified according to zones based upon the anatomic level of amputation (Figure 104-13).3 Zone I injuries occur distal to the bony phalanx. These do not result in the loss of function and rarely result in a cosmetic deformity. Management consists of cleansing, placing topical antibiotic ointment over the injured area, and then applying a layer of petrolatum gauze. This should be followed by a sterile dressing and a splint. Zone II injuries occur distal to the lunule and over the bony phalanx. These injuries often have exposed bone. Zone III injuries occur proximal to the distal end of the lunule. Zone II and Zone III injuries should be managed in consultation with a Hand Surgeon. Either type of injury may require reconstruction with a pedicle flap and/or skin grafting.3
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Trephination for a Subungual Hematoma
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A subungual hematoma is a collection of blood under the nail plate caused by blunt trauma to the fingertip. The nail bed is usually crushed or lacerated with resultant extravasation of blood into the plane between the nail plate and the nail bed.11 As pressure builds up, compression of nail bed nerves occurs and often causes significant pain. Usually this pain is what causes the patient to seek medical attention. The management of subungual hematomas is discussed separately because these injuries are typically minor and treated by simple trephination. A complete discussion of the management of subungual hematomas can be found in Chapter 102.
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It is generally accepted that subungual hematomas <50% of the nail plate may be managed conservatively by simple trephination (puncture) of the nail plate.2,5,6,11,17,20,21 This allows for drainage of blood and immediate pain relief. No anesthesia is usually necessary for this procedure. Ideally, this is accomplished with the use of an electrocautery device creating a 3 to 4 mm hole in the nail plate overlying the hematoma. The nail plate should be clean and dry for this procedure. If an electrocautery device is not available, a heated paperclip may be used.5 Refer to Chapter 102 for more complete details of the procedure.
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Some controversy exists over the management of subungual hematomas >50% of the nail plate. The concern is that a larger hematoma may hide an occult laceration that requires repair in order to avoid the complication of step-off with subsequent ridging as the new nail grows back. Some authors feel that it is impossible to accurately assess the amount of damage beneath a subungual hematoma unless the nail plate is removed to directly inspect the nail bed.6,21 These authors noted that subungual hematomas that have separated greater than 50% usually have lacerations that require repair. Another study found that a subungual hematoma with more than 50% separation had a 60% incidence of having a nail bed laceration that required repair and up to a 95% incidence when there was an associated phalanx fracture.21 In contrast to these studies, a prospective study found no complications at 6 months follow-up for subungual hematomas treated by electrocautery trephination alone.2,20 This was regardless of the size of the subungual hematoma or the presence of a fracture. These authors feel that removing the nail plate and attempting repair may actually cause further trauma to the nail bed.20
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It was previously recommended that radiographs be obtained to rule out a fracture for all hematomas larger than 50% of the nail plate. A newer study found no correlation between the size of the hematoma and the presence of fractures.20 If a fracture is suspected, have a low threshold to obtain plain radiographs prior to evacuating the hematoma.
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In summary, most subungual hematomas may be treated by simple nail trephination using an electrocautery device. This procedure will lead to beneficial drainage only if done before 36 to 48 hours from the time of the injury.11 The clinical benefit of nail bed repair with larger subungual hematomas is controversial. It may be prudent to maintain a lower threshold for nail bed repair with a larger subungual hematoma, particularly if an ideal cosmetic outcome is desired.