Nail Surgery

Timothy W. Crislip

Jeffrey S. Boberg

Pain associated with an ingrown toenail is a common presenting complaint in a foot surgeon’s office. The term ingrown nail and onychocryptosis are often used interchangeably. A cryptotic nail is an incurvated nail margin. Once the nail margin has penetrated the skin, it can be considered ingrown. Regardless of etiology, the end result is increased pressure from the hard nail plate on surrounding soft tissues. Ingrown toenails can cause considerable disability and functional limitation. Often, there is a delay in seeking treatment until the pain is unbearable, along with multiple attempts at “bathroom surgery” to correct the condition. Though temporary pain relief can be attained by this means, it usually merely delays definitive treatment. Postponing treatment for an ingrown toenail can have untoward consequences, potentially progressing to serious soft tissue infection and possibly osteomyelitis (1).

The etiology of an ingrown toenail can be multifactorial. Traumatic, biomechanical, congenital, and systemic processes can all result in an ingrown toenail. Traumatic factors such as improper footwear, poor grooming habits, or blunt trauma can result in abnormal nail fold pressures or development of nail spicules. Biomechanical abnormalities such as pronation, hallux abducto valgus, hallux extensus, or frontal plane malalignment of the digit have all been implicated (2). Congenital factors include hyperhidrosis, hypertrophic nail folds, and phalanx shape (3,4,5,6 and 7). Systemic diseases such as hemophilia, iron deficiency anemia, pulmonary fibrosis, lymphedema, and diabetes mellitus can all cause nail changes that can increase incidence of an ingrown toenail (8,9).

FUNCTIONAL ANATOMY

The nail unit consists of the nail plate, nail bed, nail folds, germinal matrix, and supporting neurovascular structures. The nail plate is a specialized keratinized structure consisting of high sulfur content and low lipid content (10). The nail plate consists of three layers (11). The upper layer is thin and brittle. The middle layer is the most dense and thick and is responsible for the bulk of the nail plate. The bottom layer is thin and is continuous with the underlying nail bed. This bottom layer contains a series of longitudinal grooves, which interdigitate with corresponding grooves from the nail bed. This is similar to rete pegs between the dermal and epidermal layers of skin (11).

The nail bed consists of thin epidermal and dermal tissue. There is a thick vascular network within the nail bed that provides nourishment to the overlying nail plate. The distal aspect of the nail bed terminates under the free edge of the nail plate at the distal nail groove. In this area, there is a transition to normal epidermal and dermal thickness of skin; this area is termed the hyponychium. The proximal aspect of the nail bed becomes continuous with the germinal matrix.

The lateral aspects of the nail plate rest in corresponding nail grooves. Each groove is overlapped by a lateral nail fold, also termed ungualabia. The transition from lateral nail bed to lateral nail fold is marked by an increase in epidermal thickness, resembling normal skin.

The proximal nail fold is a specialized structure containing two surfaces (12). The dorsal surface is continuous with the dorsal digital skin. The ventral surface faces the nail plate and matrix and is termed eponychium. Extensions of the eponychium from the underside of the proximal nail fold form the cuticle. As basal cells rise from the germinal matrix, they encounter pressure from the proximal nail fold that forces them to move distally, rather than growing dorsally.

The germinal matrix is the center of mitotic activity and maturation of nail plate cells. The matrix is thin proximally and lies on the periosteum of the phalanx in this area. At the proximal aspect, the matrix flares laterally, which is termed the lateral horn. The matrix is covered by the eponychium proximally and extends distally under the nail plate to transition to the nail bed. This is visible as the lunula, the pale crescentic area visible through the nail plate.

PATHOLOGIC ANATOMY

Onychocryptosis refers to the abnormal incurvation of nail plate edges and is a common finding. Krausz reported on 7,670 patients over a 28-year period and found that 1,982 (26%) exhibited onychocryptosis (13,14). Although many ingrown nails exhibit onychocryptosis, a prospective, matched control series studying geometric parameters of nail shape found no difference between the shape of nails in patients admitted for ingrown nail surgery and nonaffected controls (15). A recent study by Mozena (5) found ungualabia fold measurements of a mean of 4.7 mm in 25 patients with ingrown nails, compared to a mean of 1.7 mm in 100 nonaffected patients. Pediatric literature has repeatedly found association between infant ingrown nails and hypertrophied nail folds (3,4). Shape of the base of the proximal phalanx has been found to influence the shape of the proximal nail plate, but this influence is decreased as the nail plate moves distally and assumes a more normal shape (6). An upturned morphology of the distal phalanx has also been implicated (7).

Though etiology is debatable, an abnormally increased pressure from the keratinized nail plate exerted against lateral nail grooves and folds is the net result. Prolonged pressure leads to callus formation and possible penetration of skin. After the nail penetrates the dermis, a foreign body reaction is incited by the nail (16). This results in inflammation, drainage, and formation of granulation tissue. Resulting edema compounds the situation. The break in the skin barrier provides opportunity for the ingrowing nail to become secondarily infected, termed paronychia.

CLINICAL PRESENTATION AND EVALUATION

Patients may recall specific trauma and often relate multiple occurrences. Published reoccurrence rates vary from 0% to 86% (17). The hallux is affected more often than the lesser digits (18). Males are predominately affected at a ratio of 3:1 (17). There is greater frequency in adolescents and young adults (15 to 40 years) (17).

Clinically, patients present with a painful, edematous, erythematous digit with drainage varying from serous to purulent. The most common causative organism is staphylococcus, though pseudomonas and candida can also be involved (19,20). The area is usually malodorous, and abundant granulation tissue may be present. Edematous or hypertrophic nail folds obscure evaluation of nail borders. Often, ingrown nail borders and spicules cannot be fully appreciated clinically until after avulsion. Superficial dessication of exudate may occlude further drainage, resulting in formation of abscess, seroma, or hematoma, often causing lysis of the nail plate. Nail folds may become macerated from the abundant drainage.

Standard radiographs are helpful in determining if there is any underlying osseous pathology but are rarely required. Subungual exostoses, osteochondroma, enchondroma, bone cysts, or an upturned distal aspect of the distal phalanx can contribute to an ingrowing nail. If the condition is chronic and osteomyelitis is suspected, an MRI will allow diagnosis and surgical planning.

The differential diagnosis for an ingrown toenail includes both benign and malignant neoplasms (10,19). The most common benign lesion is the verruca. Fibroma, neurofibroma, fibrokeratoma, myxoid cyst, pyogenic granuloma, glomus tumor, and keratoacanthoma are all benign lesions that can involve the nail bed and nail fold. Malignant lesions include squamous cell carcinoma, Bowen disease, basal cell carcinoma, and malignant melanoma. Slow healing ulcerations should raise suspicion of benign or malignant neoplasm; biopsy of the affected area can be used for diagnosis.

CONSERVATIVE TREATMENT

Patients presenting with mild occurrence in which the lateral nail border can be visualized within the nail groove may respond to a simple slant back procedure to remove to offending edge. If patient nail folds are edematous from inflammation, often simply taping the nail fold in a plantar position away from the nail edge can relieve the pressure (21). Placing cotton inserts or flexible plastic tubing under offending borders has been described in the literature (22,23,24 and 25). Tension wiring of borders has also been described (18). Mild formations of granulomatous tissue may be relieved with serial silver nitrate application.

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