Nail bed injuries and deformities of nail
Abstract
Nail bed injuries are common and management of these requires good knowledge of the nail bed anatomy. Proper management of these injuries will ensure good healing and prevent late deformities. When loss occurs it is challenging to reconstruct which can be done by grafts or microsurgical reconstruction to restore aesthetic appearance of fingers.
ANATOMY OF NAIL
Nail is a specialised structure found only in primates although other mammals have modification of these. The nail helps to increase the sensory perception in the pulp and helps in picking up small objects. Nail loss or deformity is not only unaesthetic in appearance but can be functionally incapacitating. A proper knowledge and understanding of nail anatomy is very much essential for proper treatment of various conditions affecting it. Nail forms at approximately 10 weeks of intrauterine life from sole plate appearing on dorsum of each finger.[1] At birth a well-grown nail indicates maturity of the foetus.
The perionychium refers to the nail and surrounding structures including the hyponychium, nail bed and nail fold. Eponychium refers to the soft tissue proximally on the dorsum of nail continuing to the dorsal skin. The fine filamentous material attaching nail to eponychial fold is the nail vest. Underneath the nail plate there lies the nail bed. The white arc on the nail just distal to eponychium is the lunula. The nail bed distal to this is the sterile matrix and proximal to that is the germinal matrix. The nail fold consists of the germinal matrix and eponychium. Below the distal attachment of the nail with the pulp skin is the plug of keratinous mass called hyponychium, which is rich in polymorphs and lymphocytes which act as a barrier to infection. The term paronychium refers to the fold on each lateral aspect of the nail [Figure 1].
The germinal matrix is responsible for 90% of the nail growth. The nail is formed by the keratinous mass pressed between the nail bed and the eponychial fold and grows distally. The eponychium contributes to the shine of the nail. The nuclei are present initially which later disappear. Hence, distal to the lunula the nail becomes translucent and the underlying nail bed appears pink. The nail can be adherent only to the nail bed and any disruptions can lead to non-adherence. The nail grows at a rate of 0.1 mm per day and is fast in younger people. It is also faster in the fingers than in the toes.
CAUSES OF INJURIES
The most common cause of acute and chronic nail bed deformity is trauma. The aetiological factor may be industrial as in crush injuries due to machines, road traffic accidents or sometimes even in the sports where it gets hurt by a ball or a weight. These result in closed or open injuries. The nail bed gets squeezed between the hard nail and distal phalanx resulting in simple or complex lacerations. Sharp lacerations can occur when objects land with enough force to penetrate the nail plate. Avulsion injuries can result from crush or grinding type injuries. This can result in partial loss of nail bed also. Iatrogenic injuries can occur from traumatic nail plate removal for procedures or during placement of K wires. Self-inflicted injuries happen in conditions as nail biting or insertion of artificial nail or improper manicure. Proper management of these injuries is essential not only to get them to heal quickly but also to prevent complications and the resultant late deformities.
TYPES OF INJURIES
Injuries can be classified based on the nature and anatomic location of injury. By nature they may include simple or complex lacerations, avulsion injuries, amputations or associated paronychial injuries or fractures. A thorough assessment of the injury preferably under block or anaesthesia is essential to find the extent of damage so that repair or replacement of the injured structures can be made.
Closed injuries
Closed injuries to the nail can happen when there is a mild crushing of the finger tip as in a door crush injury or when a weight like hammer falls over it. This can result in a subungual haematoma – collection of blood between the nail bed and the nail plate.
Traditionally it has been said that if the surface area of haematoma is less than 50% of the nail surface area or the patient is asymptomatic and if the X ray does not show any fracture it may be managed conservatively. If the surface area is more or if the patient is very symptomatic it requires drainage by drilling holes in the overlying nail using aseptic precautions to prevent chances of infection. Recent studies show that if the nail is not unduly elevated and not displaced it can be managed by trephination of the nail. The trephination can be done with a hot wire and less preferably by a large bore needle like 18 G needle which can injure the nail bed if not handled carefully.
If the X-ray shows any fractures it is better to remove the nail plate, look for the laceration and repair it using fine absorbable sutures such as 6-0/7-0 chromic cat gut [Figure 2]. This effort will by itself help a good reduction of fracture, more so in the case of children.
(a) Nail bed injury with subungual hematoma.(b) Nail bed laceration seen after removal of nail. (c) After nail bed repair.(d) Healed nail bed with new nail growing
The wound heals in a period of 2 weeks and till that time it is covered with non-adherent dressings. The new nail will grow completely at around three months. Till a period of three weeks a protective splinting for the finger is advised either by a volar slab or a finger splint.
Replacing the nail plate is generally not recommended except in case of comminuted fracture of distal phalanx where it can splint the bone or in cases of lacerations in the nail bed and eponychial fold where its interpostition can prevent formation of synechiae between the nail bed and the eponychial fold. It is very important to prevent collection of blood underneath it to avoid any further complications such as infection. This can be done by making a hole in the nail in an area not overlying the nail bed laceration. The nail will be lifted off by the newly growing nail. If the nail plate is not available, a non-adherent gauze will do the same function. If available, mouldable meshed titanium plate can be used.
Open injuries without nail bed loss
In these cases the nail plate may be partially or totally avulsed exposing the underlying laceration in the nail bed or the fracture sites. If the nail plate is still partially attached it may be removed using a blunt instrument between it and the nail bed gently. The management is similar to that which is described previously by suturing the nail bed and splinting the finger for three weeks when the fractures will heal. The amount of soft tissue attachment on the volar side may vary which determines the vascularity of the tip. Care should be taken not to disturb this attachment and jeopardize the vascularity of the finger tip. If the laceration extends on to the paronychium it has to be repaired meticulously. Even if the laceration is very complex, very often all the pieces survive if sutured meticulously.
Approximately 50% of nail bed injuries are associated with distal phalangeal fracture. A majority of these are comminuted tuft fractures which do not need any specific treatment. Good approximation of the nail bed not only restores the good fracture reduction but also prevents scarring the nail bed which may give rise to deformities of nail like ridging or narrowing of the tip. If the injury is proximal it may need additional procedures like two parallel K wire fixation or placing the nail plate as a splint and anchoring it with a figure of 8 suture to retain it in place.[2–4] [Figure 3]
Nail bed loss
Nail bed is very essential for the growth of the nail and in its absence the nail cannot be adherent and can be deformed. Any area of nail bed loss can be managed by replacing it with a split thickness nail bed graft which can be harvested from the adjacent nail bed when the loss is very small or from the great toe nail when it is large. It is harvested using a 15 blade scalpel. These grafts take surprisingly well over the distal phalanx.
In case of loss of distal part of the nail bed if there is bony support it can be placed as a graft. If not the exposed bone can be covered with a local V-Y advancement flap and the nail bed graft may be placed over the advancing edge of the flap which gives gratifying results[5] [Figure 4].
(a) Stumps of both thumbs. (b) Amputated thumb tips. (c) After advancement of VY flaps.(d) With nail bed grafts in position. (e) Late postoperative picture with nail growth
In case of total loss of nail bed with scarring vascularised nail bed grafts can be used which transfer the nail from the great toe or second toe by microvascular transfer.[6]
Nail bed avulsions
Sometimes the nail bed is intact but avulsed from the germinal matrix with the fracture of bone. In this case it is reattached to the sulcus using mattress sutures [Figure 5]. This by itself will reduce the fracture and get the bone properly aligned and only very rarely a K wire is needed to the fix the fracture. If proximal nail bed is available it can be approximated with 6-0/7-0 chromic catgut.
Amputations
In case of very distal amputations in young children less than a year the whole amputated part can be defatted and applied as a composite graft. [Figure 6]. In older children this can be attempted but may not give equally good results.
Deformities of the nail
Deformities of nail can be caused by very simple subconscious habits like biting of nail, picking objects using the nail or prying the eponychial fold, etc. This causes elevation of nail at distal part and breaches the protection offered by the hyponychium at the distal end. Once the patients are pointed out about stopping these activities the nail shape is usually restored.
Eponychial loss
This can happen after trauma or tumour resection such as wart excision. This results in rough nail lacking the shine. This is best treated by replacing the eponychium as a composite graft harvested from a toe. Some amount of success has been reported in burn patients also.
Onycholysis (non-adherence)
This can happen due to trauma, irritation, fungal infection and over production of sterile matrix keratin. Waiting for adequate time after treating the underlying cause can result in cure of this problem. A nail requires three or four growth periods to improve its shape, volume and appearance.
Trauma
Trauma may cause scarring in various directions in the nail bed – longitudinal, oblique or transverse. If the scar is very narrow adherence may not be a problem but if it is wide it results in non-adherence. In these cases the nail is removed and the scar assessed. If it is narrow it can be excised and tension free closure of nail bed can be done. If closure is not possible replacing the scarred area with a nail bed graft can be done.
Ridged nails
Ridges occur longitudinally from cicatricial build up in or beneath the matrix with nail assuming the shape of the matrix. To correct this, the matrix or deeper ridge must be excised surgically. Transverse ridges can be caused by regrowth after trauma or hypoxia.
Split nails
A longitudinal or oblique scar may result in split nail deformity as the scar cannot produce nail and the surrounding pull splits the nail. Treatment is by removal of nail and proper repair or grafting of the nail bed after excising the scar. If the scar involves the germinal matrix it needs a germinal matrix graft.
A horizontal scar in the germinal matrix region can create a double nail. The volumes of dorsal and volar portions may vary. Treatment is by excising the scar and suturing.
Pincer nail
This is characterised by progressive transverse tubing of the nail extending over the distal edge. Approximately 60% of the individuals have pain and the nail bed vascularity may be compromised. The aetiology is unknown and has been attributed to trauma, tight shoes (in the region of thetoes) and heredity. Various treatments like weakening of nail by grinding it and excision of lateral folds have been proposed. One useful technique is to separate the paronychium from the periosteum and move it laterally.
Bony irregularities
This may be due to malaligned distal phalangeal fractures. This may be corrected by lifting the nail as proximally based flap, visualise the area and rasp it. In case of depression in the bone filling it up with a bone graft has been recommended.
CONCLUSIONS
Proper knowledge of nail anatomy is essential for treating these injuries effectively, preventing deformities and getting good results with patient satisfaction.
Footnotes
Source of Support: Nil
Conflict of Interest: None declared.