A 63-year-old woman presents with a nail deformity present for 2 years. She recalls a stabbing injury to her proximal nail plate while performing a self-manicure. The aesthetics of the nail was displeasing; she lacked normal nail growth and adherence (▶Fig. 1.1). She did not seek care after the initial injury and the deformity did not improve after multiple nail cycles.
Nonadherence of the nail (onycholysis) is the most common posttraumatic nail deformity. This occurs secondary to nail bed scarring and is often found immediately distal to transverse or diagonally oriented nail bed scars or bone irregularities. The scar interrupts the progressive addition of nail cells from the sterile matrix to the volar nail plate causing detachment of the nail. The nail is unable to reattach to the nail bed distally. Distal nonadherence may lead to problems with subungual hygiene, an unstable nail when picking up small objects, pain from repeat avulsions when catching the nail on objects, or simply aesthetic concerns.
Fig. 1.1 Nonadherence of the nail plate. Right thumb nail of a 63-year-old woman. This patient suffered a sharp traumatic injury to the proximal nail bed 2 years earlier.
The rate of complete nail progression from nail fold to free margin is 70 to 140 days. Baden describes a 21-day delay in growth after injury, during which time the nail thickens proximally but does not grow distally. Distal growth of a thicker-than-normal nail proceeds for the next 50 days, followed by growth of a thinner-than-normal nail for 30 days. Nail growth is not normal for approximately 100 days after injury.
The hard and elastic structure of the nail plate is produced continuously by the nail matrix. The germinal matrix, sterile matrix, and dorsal roof of the nail all produce the nail, with the germinal matrix producing the majority (90%) by gradient parakeratosis. The sterile matrix adds cells to the volar surface of the nail, accounting for the attachment of the nail to the matrix. The dorsal roof of the nail fold adds flattened cells to the dorsal surface of the nail, producing shine to the nail. The nail is transparent; however, it appears pink due to the presence of vessels of the underlying nail bed. The lunula appears white due to the presence of nuclei. The nail bed consists of the germinal and sterile matrices. The germinal matrix makes up the ventral floor of the proximal nail fold. The sterile matrix consists of the soft tissue immediately beneath the nail distal to the germinal matrix. Keratinization of the nail matrix cells occurs along an oblique axis. As a result, the proximal part of the nail matrix produces the dorsal portion of the nail plate and when damaged gives rise to the development of nail plate surface abnormalities, whereas the distal part of the nail matrix produces the ventral portion of the nail plate.
The patient suffered a penetrating injury to the proximal germinal matrix, which created a disruption in the creation, growth, and strength of the dorsal nail. Injuries distal to the germinal matrix generally do very well; however, proximal nail bed injuries, in particular if unrepaired, often lead to chronic, displeasing nail plate appearance. Since the patient did not seek immediate care after injury, the differential diagnosis also includes fungal infection and skin malignancy (▶Fig. 1.2). Burn injuries to the fingertips often destroy the specialized cells of the nail matrix and result in chronic nonadherence (▶Fig. 1.3)
This patient’s problem may have been prevented by immediate repair of the injured nail bed. The patient elected to ablate the nail and cover with a skin graft from the volar wrist. Split-thickness skin grafting can be sufficient, although full-thickness grafts are straightforward to harvest and the donor site closes primarily.
Options for improving this patient’s nail bed include the following:
• If the scarred germinal matrix can be identified, it can be excised and closed primarily in hopes of an improved nail adherence and aesthetic.