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Fingernail Avulsion and Injury to the Nail Bed

Roberts, James R. MD

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    Learning Objectives: After reading this article, the physician should be able to:

    1. Discuss the anatomy of the fingernail and fingertip.
    2. Describe the injuries to the nail bed that can be repaired in the ED.
    3. Summarize the principles of nail bed repair and nail replacement.

    The emergency physician can and should repair most fingertip injuries, and the process is accomplished by following a few basic principles. Most treatment plans begin with an understanding of the anatomy of the nail and nail bed and a knowledge of the healing process.

    Some fingertip injuries are complex and best left to the hand surgeon, but the majority can be handled by an educated EP. The clinical approach to patients with traumatically avulsed nails, crush injuries, or significant nail bed lacerations follows accepted principles, but some of these axioms are shrouded in myth and misconception, or seemingly kept secret by a cadre of clinicians who are willing to tackle them in the ED.

    As with subungual hematomas, discussions in medical textbooks tend to be inadequate about the more complex fingertip injuries that can result in cosmetic or functional deformities. Armed with a few basic principles and the time to use them, however, the emergency physician can and should repair the majority of fingertip injuries that do not require extensive revision or fancy grafts or flaps. The fingertip is rather forgiving and recovers quickly, and usually one can obtain good functional and cosmetic results when a few basic rules are followed.

    The Deformed Fingernail, A Frequent Result of Failure to Repair Nail Bed Injuries Ashbell TS, et al J Trauma 1967;7(2):177

    This article is 36 years old, but it remains a classic description of nail bed injuries. Some of the information concerning grafts and flaps for the treatment of fingertip injuries is dated and not currently advocated, but the discussion on nail bed injuries is timeless. The authors note that medical textbooks frequently neglect the subject of the, deformed, or split fingernails as a result of injury. The proper primary treatment of the nail and nail bed will prevent most fingertip deformities and minimize cosmetic or functional problems.

    Figure 1:
    Anatomy of the fingernail. The fingernail arises from the germinal matrix (under the eponychium), and rests on the nail bed or sterile matrix. The overlying tissue covering the proximal nail is the eponychium (also termed the cuticle), and the potential space between the nail and the eponychium is the nail fold. This nail fold is the area where a paronychia begins. The half moon seen under the proximal nail is the distal end of the germinal matrix. The fingernail is firmly attached to the nail bed at the sterile matrix, but loosely attached at the base over the germinal matrix.

    This review article is based on the authors' experiences with more than 3,000 nail bed and nail root injuries, and is accompanied by numerous instructive illustrations and diagrams. The author notes that it is important to understand the anatomy of the nail bed and nail root and the intricacies of nail growth to treat injuries adequately. Nails are ectodermal appendages covering the dorsal aspects of the digits.

    These structures provide protection and integrity to the fingertip, and allow precise and delicate touch, skilled hand functions, and the ability to pick up tiny objects. These functions are disrupted when the anatomy is disrupted. The distal border of the nail is free, but the proximal border is tucked into a fold, and is covered with a skin flap called the eponychium or cuticle.

    The nail is attached at its lateral, distal, and proximal borders. The nail bed (also called the matrix) anchors the dermis to the periosteum of the distal phalanx. The matrix is made up of the sterile matrix, the structure upon which the grown nail sits, and the germinal matrix, a continuation of the sterile matrix. The germinal matrix lies protected under the eponychium, forming the area from which the nail is produced. Growth takes place in the nail root, or lunule.

    The lunule is the pale crescent-shaped structure easily recognized under the proximal portion of the nail. Importantly, the nail is not firmly attached at the lunule and only weakly attached to the root. Because the nail is formed in the germinal layers of the root, loss or deformity of the nail root results in permanent loss or permanent deformity of the nail. As the nail grows distally, the more superficial cells become cornified. Distal to the lunule, the nail is firmly attached to the nail bed or sterile matrix. Complete regrowth of an avulsed nail usually requires four to five months (1 mm per week).

    This is a common injury that occurs when a finger is smashed in a door, left. Note that the base of the nail is avulsed from the nail fold and lies on top of the eponychium, but it remains attached distally. X-ray revealed a nondisplaced tuft fracture, an incidental finding. With these injuries, be sure to check for integrity of the extensor tendon (mallet finger). This injury requires removal of the nail, anatomic repair of the nail bed laceration, and a procedure that keeps the eponychium from scarring down to the germinal matrix until the new nail grows. The nail avulsion at right requires replacement of the nail under the cuticle. This injury was minimally crushed, and the distal nail was firmly attached, so the cuticle was simply lifted up and the avulsed nail replaced under it. The nail bed did not require repair.

    There are a few well supported treatment principles that must be adhered to when approaching fingertip injuries. A basic tenet includes thorough cleaning with minimal debridement of the nail bed and nail root. It is paramount to reposition and anatomically repair significantly disrupted nail beds and nail roots accurately. Improper alignment of injured structures will be followed by deformed nails. Close approximation of the nail bed is an absolute necessity. It also is important to preserve the skin folds surrounding the nail margins. Adhesions between the eponychium, nail bed, and root are prevented by maintaining this space with either the replaced nail or gauze packing.

    Wide scars or misalignment in the skin fold can result in splitting or permanent deformity of the nail when it regrows. Although some deformities may be repaired with excision of the scar tissue and revision at a later date, often this is a permanent deformity. Fractures of the distal phalanx should be anatomically reduced.

    Other injuries noted include ingrown nails when the lateral folds are not maintained, widened nails that result from unrepaired lacerations or nonreduced fractures, narrow nails that result when the nail bed is allowed to grow inward because lacerations were not approximated, and protruding nonadherent nails secondary to unreduced dorsally displaced fractures.

    Comment: This article is difficult to describe, and should be read to appreciate the numerous diagrams and illustrations. Although complicated crush injuries resulting in significant tissue loss or deformity are best treated by a consultant, many common hand injuries seen in the ED can be handled by the well informed EP. As with most injuries, the initial repair largely determines the final outcome. Plastic surgeons can fix some things later, but not even the most skilled consultant can undo all damage done by an uninformed primary physician.

    A common injury is a crush injury of the fingertip with avulsion of the base of the nail. It is often a complication of getting one's finger caught in a car door. A common scenario is a child chasing a sibling into the bedroom. The first child tries to slam the door to halt the pursuit, catching the pursuing child's hand between the door and the door jam. Because the nail is not as firmly attached at the base or lunule as it is to the distal nail bed, the flexion injury avulsed only the base, and the proximal nail now lies on top of the eponychium. Occasionally the entire nail bed may be avulsed, but more often than not, the bed is only lacerated.

    When attempting repair, one first checks for an avulsion of the extensor tendon. In the excitement and anxiety of a crush injury, this may be overlooked, and the resultant mallet finger may actually be more of a long-lasting cosmetic concern than the nail injury. Always test the finger for the ability to fully extend the distal tip. With these injuries, an x-ray is usually mandatory because fractures should be reduced. Minor fractures are easily reduced, but some may require fixation.

    Following digital block with bupivacaine, the loose nail can be totally removed to facilitate surgical repair of the nail bed. The least traumatic way to remove the nail is to place the closed blades of small iris scissors between the nail and nail bed and gently advance and separate the blades. A scalpel can be used, but this tends to lacerate the bed. A tourniquet is an essential part of any procedure, and it is unthinkable to proceed without one. I also like to prep the avulsed finger, put a sterile glove on the patient, and cut out the involved finger to obtain a sterile field.

    Under digital block with bupivacaine, the essential bloodless field is obtained by a tourniquet, and the extent of the nail bed laceration is determined, left. To obtain a sterile field, the patient's hand is covered with a sterile glove and the distal finger is cut out to expose the field. This eliminates the need to cover the field with a paper drape that usually falls off or covers the field during suturing. The nail may be gently removed by spreading small scissors placed between the nail and nail bed, allowing the nail bed to be anatomically repaired with 6-0 absorbable sutures, right.

    This does away with annoying paper drapes that invariably fall off, and it certainly impresses a surgeon who may be wandering through the ED. If you choose a tight-fitting glove, you can just cut off the he material proximally to base of the finger; this squeezes out venous blood for less oozing and also makes a nice tourniquet.

    Once the nail is removed, it is gently washed, not debrided and only minimally trimmed, and kept for possible use as a dressing. For the prep, I prefer to use the sink and tap water, then a final rinse with sterile saline. The proximal portion of the nail is soft and pliable. It is best to leave this area intact rather than trim it; just make sure this area lies flat when replaced in the nail fold. It should be noted that the loss of the nail itself is actually a minor problem. If the nail root is repaired properly or has not been injured in the first place, a new nail will grow and be indistinguishable from the original one.

    The nail bed is now ready for repair. The aim of the surgery is to provide a flat, smooth surface on which the new nail will grow and to approximate the nail root from where a new nail will originate. Uneven nail beds will lead to permanent grooves and ridges in the new nail. As noted, failure to repair the root of the nail can cause a wide scar to form and lead to a permanently split nail.

    Replacing the nail is the easiest way to protect the healing nail bed, pack the nail fold, and provide a natural splint for the healing injury

    The actual nail bed repair should be accomplished with absorbable sutures, usually 6-0 size. Amazingly, I still see residents perform intricate repairs with nylon sutures that have to be removed. It is important not to debride the nail bed extensively. The tissue in the nail bed is extremely hardy and resilient, and unlike skin, tenuous flaps frequently survive when approximated.

    Less than perfect closure or coverage often gives a better cosmetic result than extensive debridement. Grafting may be required in some cases. Small detached pieces of bone may be carefully removed prior to closing the nail bed. Displaced fractures can usually be easily reduced.

    A laceration involving the nail bed, germinal matrix, and skin fold must be carefully approximated, left. First, the nail is completely removed, center. Fine absorbable sutures are placed under a bloodless field provided by a finger tourniquet. The avulsed nail or a gauze pack is gently placed between the matrix and eponychium for two to three weeks to prevent scar formation. If the original nail is replaced (the best option), it may be sutured or taped in place, second from right. A large hole in the nail will allow for drainage, right. The old nail is pushed out by a new one. If the nail matrix is replaced quickly and atraumatically, the nail may act as a free graft and grow normally.

    After the nail bed repair is performed, it is most important to preserve the skin folds surrounding the nail and the space beneath the eponychial fold. This is accomplished either by replacing the avulsed nail or keeping the space open with a gauze packing. This prevents adhesions between the eponychium and nail bed/root. It's easiest to replace the patient's own nail because packing this small space with gauze is technically more difficult. The entire original nail is gently repositioned with forceps after the nail fold is cleared of blood clots.

    Make sure the soft edges of the proximal nail lie flat in the fold. I personally place a few drain holes in the replaced nail and then suture it in place, but it may be held tightly with steristrips. Nylon sutures (4-0) will penetrate the lateral skin and nail, and hold it firmly in place during dressing change and hand washing. Don't put sutures through the nail root.

    Antibiotics are optional. This is a concept that is difficult for many physicians to accept, especially if the phalanx is fractured. I usually don't prescribe them unless the patient is immunocompromised. It's not unreasonable, however, to use three or four days (but not 10 days) of Augmentin, Keflex, or Cleocin.

    Antibiotic prophylaxis has been studied, and there are no data demonstrating benefit. For the first few days, a plaster volar splint rounded at the end to protect the fingertip is helpful. Elevation is stressed. I opt for a wound check in three days with a dressing change. I remove the sutures in the nail or the gauze packing under the eponychium. in two weeks. At this point, the raw nail bed is much less sensitive and occasionally the replaced nail has begun to grow. If the nail does not take as a graft, a new nail will slowly push off the replaced nail.

    Dressing of the Nail Bed Following Nail Avulsion Dove AF, et al Hand Surgery (Br) 1988;13(4):408

    Following nail avulsion, the raw nail bed is often dressed with a variety of supposedly nonadherent materials. Patients may experience considerable pain at dressing changes because, despite manufacturer's claims, these dressings invariably stick to the nail bed. Removal causes bleeding, so that even a replacement dressing becomes adherent as well.

    A variety of impregnated materials and sponge-type dressings have been advocated to facilitate the growth of new epithelium, allow passage of oxygen and fluid from the wound site, and to make dressing changes easier and less painful for the patient. The authors of this paper compared a polyurethane sponge, a paraffin-gauze, and the replacement of the avulsed fingernail as dressings for injured nail beds.

    The 156 cases described in this paper included patients with injuries severe enough to require removal of the fingernail for repair of an injury. Patients with diabetes or peripheral vascular disease were excluded. Dressings were applied according to manufacturers' recommendations. The avulsed nail was anatomically positioned and held in place with a dressing (without suturing). Dressings were changed at seven, 14, and 21 days. During the dressing change, the patients recorded their pain scores, and nurses noted the adherence properties of the dressing, signs of infection, and extent of healing.

    Those whose nail bed dressings consisted of the replaced nail had significantly less pain at the first redressing compared with other modalities. Although the difference in pain was not statistically different among the groups at the second or third dressing change, there was a tendency toward the replaced nail group to continue to have less pain. Likewise, the adherence of the dressing was significantly greater in the sponge and gauze group compared with the replaced nail group. There was no difference in the rate of healing or incidence of infection.

    The authors were not able to show any advantage of the synthetic dressings over native nail replacement. Nails were not sutured in place as recommended by some authors, but they were simply tucked under the nail fold and held in place with a gauze dressing. Even when only half the nail was left, it was a suitable dressing and appeared to be enough to reduce the pain and adherence of the overlying dressing. Most of the replaced nails (37 out of 49) remained in place with this simple technique, and some replaced nails took as a free graft and grew normally following replacement. The authors advocate nail replacement as the dressing of choice in patients with fingertip injuries with nail avulsion.

    Comment: This study basically demonstrates that there is no such thing as a nonadherent nail bed dressing. I have had similar clinical experiences so I routinely replace the patient's lost nail, even when only part of the original structure is available. I do, however, continue to see patients in follow-up that have gauze placed over the nail bed only to have them bleed when changed or require digital block for dressing removal.

    One could make the point that it is not routinely necessary to remove dressings that are stuck to the repaired nail beds. Some colleagues merely place a piece of Vaseline gauze over the sutured nail bed and allow it to separate spontaneously in two to three weeks. Only the overlying, bulky absorbable dressing is periodically changed, eliminating the pain and bleeding that invariably accompanies attempts to replace an entire dressing.

    This approach works well and is not particularly problematic, although I still believe that the replaced nail is the easiest way to protect the healing nail bed, pack the nail fold, and provide a natural splint for the healing injury. Even if it is only partially present, the native nail can be replaced to provide a physiological dressing. Minimally traumatized avulsed nails can actually grow normally if carefully replaced in their proper anatomic position.

    © 2003 Lippincott Williams & Wilkins, Inc.