Disorders of Nails

Anatomy

The normal nail complex consists of the nail plate, the nail bed, and the surrounding skin. The nail plate is the nail proper and consists of two components: the root, the portion of the nail plate that is beneath the skin, and the body, the exposed portion of the nail plate. The nail plate is made up of overlapping layers of keratinized cells. Beneath the nail plate, the nail bed has two components, the sterile matrix and the germinal matrix. This distal margin of the germinal matrix can be seen through the nail plate as pale, crescent-shaped tissue at the base of the nail plate. This visible portion of the germinal matrix is termed the lunula . From the distal margin of the lunula, the germinal matrix extends 5to 8 mm proximally and deep to the proximal nail fold. The germinal matrix is smoother and paler than the adjacent sterile matrix, and it contributes to longitudinal nail plate growth ( Fig. 88.1A ). Distal to the germinal matrix, the sterile matrix supplies a vascular bed for the nail plate. The margins of skin that overhang the lateral borders of the nail are termed lateral nail folds . The proximal nail fold is termed the eponychium , and its distal extension that covers the nail root and adheres to the nail plate is the cuticle . Finally, the hyponychium is the thickened skin located at the distal margin of the nail.

Many descriptive terms and definitions communicate nail pathologies ( Box 88.1 ). Although not always realized, nail pathology may be a sign of other underlying pathology. Many systemic diseases are associated with nail abnormalities ( Table 88.1 ).

Trauma

The dropping of heavy objects or activities performed without wearing shoes can cause traumatic injuries that can easily damage the nail plate, nail bed, and underlying phalanx. These injuries can cause long-term nail plate abnormalities and even nail plate loss. Abnormalities can include ridging, splitting, thickening, and discoloration. Treatment goals for nail bed and plate injuries include repairing the nail bed and maintenance of the eponychial fold to minimize future nail deformity. The sterile matrix is very vascular; hence, subungual hematomas frequently occur with trauma. Treatment of subungual hematomas remains controversial. Past recommendations have included nail plate removal for nail bed exploration and repair for subungual hematomas larger than 50% of the size of the nail or larger than 25% with an underlying fracture. More recently, others have suggested trephination alone is adequate treatment when nail margins are intact.

When nail margins are intact, we typically treat subungual hematomas with trephination or observation depending on the patient’s pain and acuity. Trephination can be done by using a heated paperclip to perforate the nail plate. The hematoma cools the paper clip, preventing nail bed injury. Other methods include ophthalmic cautery or needle perforation. Occasionally, more than one opening is required to adequately maintain hematoma decompression.

Despite the controversy, most authors agree that if a subungual hematoma is associated with unstable nail margins, then nail plate removal, exploration, and nail bed repair is indicated to prevent future aesthetic and functional problems. Laceration repairs should be completed with small absorbable suture (7-0 chromic) or medical adhesives (2-octyl cyanoacrylate). After repairing the nail bed, the nail or an alternative material (acrylic nail, aluminum foil, silicon sheeting, or other nonadherent material) should be secured over the nail bed and under the eponychium, preventing adhesions between the eponychium and the germinal matrix. Creating small perforations in the replaced nail or other material is important to prevent fluid accumulation beneath the nail. The nail can be secured with a figure-of-eight stitch or medical adhesive ( Fig. 88.2 ).

Dystrophic Nails (Onychogryposis, Onychomycosis)

Deformed nails in elderly and diabetic patients can be difficult to manage at best and catastrophic at worst, especially when associated with an insensitive foot. Having a small double-action rongeur and nail splitter-cutter in the office is recommended. These nails can be reduced quickly and safely with these instruments ( Fig. 88.3 ).

Other than reduction of the nail mass, onychomycosis, or fungal infection of the nails, can often be treated with benign neglect because its main effect is a cosmetic one. If treatment is desired to eradicate the fungal infection, referral to a dermatologist may be warranted for confirmatory testing through appropriate cultures followed by cost-effective medical treatment, either by topical or oral agents. Most treatment regimens are prolonged because it is difficult for various medications to penetrate the nail. Many of the oral medications have serious side effects, and patients should be appropriately monitored for these side effects.

The efficacy of laser therapy for onychomycosis remains controversial. Lasers are approved by the US Food and Drug Administration (FDA) for “temporary increase of clear nail in patients with onychomycosis,” but laser treatment has resulted in lower cure rates than oral and topical therapies. Hence, laser treatment is not regarded as a first line treatment for onychomycosis.

Other Lesions of the Nails

Subungual exostosis

This entity is not a primary nail abnormality; however, it is usually presented as a painful and deformed nail, leaving the examiner perplexed as to the cause of the pain and deformity ( Fig. 88.4 ). The exostosis of the distal phalanx is formed from fibrous tissue and has a fibrocartilage cap, as opposed to an osteochondroma, which is formed from enchondral ossification and has a hyaline cartilage cap. The chromosomal translocation t(X:6)(q22;q13-14) is linked to this entity, suggesting a neoplastic origin. Routine radiographs of the feet may not show the exostosis because the technique does not emphasize the distal phalanx. Radiographs taken at oblique angles and magnified are helpful. Conservative treatment is not usually successful as this lesion is progressive, and surgical excision is the treatment of choice. If the exostosis has not disrupted the nail bed, the incision should be made lateral or medial to the nail bed, elevating it off the exostosis to remove it to preserve the nail bed ( Fig. 88.4 ). If, however, the nail bed is disrupted, a dorsal incision to remove the exostosis should be used ( Fig. 88.5 ). The most common complication from surgical excision is nail deformity. Recurrence has been reported at 4%.