eMedicine Specialties > Emergency Medicine > Trauma & Orthopedics

Nailbed Injuries

Author: Darrell Sutijono, MD, Staff Physician, Department of Emergency Medicine, State University of New York, Downstate; Kings County Hospital
Coauthor(s): Mark A Silverberg, MD, FACEP, MMB, Assistant Professor, Assistant Residency Director, Department of Emergency Medicine, State University of New York Downstate College of Medicine; Consulting Staff, Department of Emergency Medicine, Staten Island University Hospital, Kings County Hospital, University Hospital, State University of New York Downstate at Brooklyn
Contributor Information and Disclosures

Updated: Jul 16, 2009

Introduction

Background

Nailbed injuries are common, with fingertip injuries being the most often seen type of hand injuries. The fingertip is frequently injured because it is the point of interaction between the body and one's surroundings in the majority of activities performed on a daily basis, and it is the most distal portion of the upper extremities.

In addition to long-term cosmetic consequences, injuries to the nail can affect daily living. The nail provides protection for the fingertip, offers the ability to pick up small objects, and plays a role in tactile sensation. It also serves as a counter force when the finger pad touches an object; two-point discrimination distance widens substantially with removal of a nail.

Pathophysiology

To fully appreciate the consequences and treatment of nailbed injuries, reviewing the anatomy of the nailbed and the surrounding tissues is useful.

• Nail - Hard structure composed of desiccated, keratinized squamous cells
• Perionychium - Composed of the nailbed and paronychia
• Nailbed - Soft tissue below the nail that is bound to the underlying periosteum of the distal phalanx and consists of the germinal and sterile matrix
• Paronychia - Lateral nail folds
• Hyponychium - Junction between the nailbed and fingertip skin that contains large numbers of polymorphonuclear leukocytes and lymphocytes, which protect the subungual tissue from infection
• Nail fold - Holds the proximal nail
• Eponychium - Commonly known as the cuticle, or the distal portion of the nail fold where it attaches to the dorsum of the nail
• Lunula - White opacity distal to the eponychium, caused by the presence of nail cell nuclei in the germinal matrix as they stream upward and distally to create nail

Nail formation is a collective production by 3 areas of the perionychium:

• The germinal (intermediate) matrix, covering the ventral floor of the proximal volar nail fold to the lunula, produces 90% of nail volume. It is immediately distal to the extensor tendon attachment to the distal phalanx. As the cells are produced, they force cells ahead to flatten and stream distally into the nail because of the confining boundaries of the nail fold. The nuclei of the cells disintegrate as they grow beyond the lunula, giving the nail its clear appearance.
• The sterile (ventral) matrix begins as the lunula ends and extends out to the hyponychium. It is closely adherent to the dorsal periosteum of the distal phalanx. It contributes a small amount to the nail but mostly provides adherence between the nail and the nailbed.
• The proximal half of the dorsal roof of the nail fold produces cells that give the nail its shine.

Longitudinal nail growth takes between 70 and 160 days to cover the entire length of the nail. After an injury, nail growth is stunted or absent for up to 21 days. The nail then grows rapidly for approximately the next 50 days and then slows again before a normal and sustained growth rate resumes. These relative accelerations and slowdowns in nail growth create the characteristic lump that is often observed on most nails that regrow after trauma.

As a result of scar tissue being unable to produce nail material, damage to specific components of the perionychium will lead to characteristic defects during regrowth of the posttraumatic nail. A scar of the dorsal roof of the nail fold creates a dull streak on the nail surface, while a scar of the germinal matrix may cause a split or absent nail, and a scar in the sterile matrix results in a split or nonadherent nail beyond the scar.

The nailbed is supplied by two volar arterial arches that are anastomoses between digital arteries of the finger or toe, just above the periosteum of the distal phalanx. Venous drainage coalesces in the proximal nailbed and proximal to the nail fold and drains over the dorsum of the finger. Abundant lymphatic vessels are present in the nailbed. The perionychium is innervated by the dorsal branches of the paired digital nerves, one to the nail fold, one to the fingertip, and one to the pulp.

Frequency

United States

The hand is involved in 11-14% of on-the-job injuries and 10% of all accident cases in US emergency departments. However, the exact prevalence of nailbed injuries is unknown since many patients with nailbed injuries do not bother to seek a physician's care for what they perceive as a minor trauma.

Mortality/Morbidity

Complications of nailbed injuries include nail loss, abnormal growth, nonadherence of new nail, splitting of the nail, soft tissue infection, and osteomyelitis of the underlying distal tuft.

Race

No racial predilection exists.

Sex

A 3:1 male-to-female predominance of injury exists.

Age

Nailbed injuries occur in all ages; however, the most common age group is between 4 and 30 years old. Fingertip injuries account for two thirds of hand injuries in children, and damage to the nailbed occurs in 15-24% of these injuries.^1,2

Clinical

History

A complete history for a nailbed injury should include hand dominance, time of the injury, the presence of an associated open wound, previous history of hand injury, tetanus status, occupation and hobbies, and the patient's overall health. All of these aspects of the patient's presentation may affect the treatment plan for the injury. Also, inquire about the circumstances of the accident, as the mechanism of injury has prognostic implications for severity of injury and wound contamination.

Most injuries of the nailbed involve the fingertip versus an isolated nailbed injury (6:1 ratio). The right and left hands are affected equally. However, the long finger is most often affected, since it is usually the last to be pulled from a situation that has the potential to cause trauma. After the long finger, the ring, index, pinky, and thumb are affected in that order. The middle and distal third of the nail are the most frequent sites of injury.

Crush and avulsion injuries as well as injuries associated with distal phalanx fractures have a worse prognosis. Injuries that span the entire nailbed or most of the bed and fold also fare worse than those that are isolated to one to two thirds of the nailbed or only to the nail fold and germinal matrix.

Physical

A general examination is necessary to rule out additional injuries.

The injured finger can usually be examined without anesthesia, although children or those in severe pain may require a digital block first. A complete sensory examination (performed prior to a digital block) as well as motor function and vascular supply is necessary. If the nail is avulsed from the nail fold and is unstable, a digital block will usually be necessary to accurately examine the extent of injury. Loupe magnification may be used if necessary.

The presence and extent of devascularized and macerated skin should be noted as the presence of active bleeding, a subungual hematoma, avulsion of the nail, disruption of the nailbed, and any specific pattern of laceration (linear, stellate, flap) of the nailbed if visible. Observe the posture of the fingers, and look for any presence of deformities signifying fracture, dislocation, or tendon avulsion, and the presence of glass, wood, metal, or other foreign body fragments.

Nailbed injuries are often accompanied by subungual hematomas, lacerations to the surrounding skin, crush or avulsion injuries to the distal finger, and associated fractures of the distal phalanx.

A subungual hematoma is a common presentation, and the possibility of an underlying nailbed laceration or injury should always be considered. Lacerations of the nailbed associated with subungual hematomas are most often stellate. Simple lacerations are uncommon unless an accompanying crushing component that was strong enough to collapse the nail through the nailbed and onto the distal phalanx or to fracture the distal phalanx occurred. Fracture of the distal phalanx usually disrupts the matrix but may not break the nail.

The nail may also be partially or completely avulsed from the nail fold. Nail plate avulsion is almost invariably accompanied by significant nail bed laceration that requires repair. Fractures of the distal phalanx are present in 50% of nailbed injuries.

Causes

Most injuries of the nailbed are due to crushing injuries, such as with a hammer. Twenty-five percent of nailbed injuries involve the finger being crushed in a doorway, most commonly car doors. Crush injuries squeeze the soft tissue of the nailbed between the nail and the distal phalanx. This may result in a simple subungual hematoma or a simple or stellate laceration. Saws, knives, drills, moving belts, and lawnmowers are also common causes of nailbed injuries.

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