Fingertip Injuries

Etiology

Fingertip injuries can be classified by the mechanism of injury or the level of injury based on the frequently used Allen classification system.[4][5]The most common mechanisms seen include the following:

• Crush injury due to forces of compression. An example is a door closing on the finger, injury with a hammer, and objects being dropped on fingers. This can present as a closed or an open injury and can be associated with distal phalanx fractures. 
• A laceration is secondary to a household instrument (knife, scissors, and cans) or works tools (rotatory saw) involving pulp or nail and/or the nail bed complex. 
• Amputations involve both soft tissue loss and partial or complete distal phalanx loss. Such injuries can cause cosmetic and functional defects.
• Other injury mechanisms are sudden flexion or extension forces leading to distal tendon avulsion injuries. 

Allen classifications are based on the four types listed below.

• Type 1: involves only the pulp
• Type 2: involves the pulp and nail bed
• Type 3: includes partial loss of the distal phalanx
• Type 4: injury proximal to the lunula

Type 1 injuries may heal quite well by secondary intention. Type 3 and type 4 often require some flap coverage.

Epidemiology

Traumatic injuries to the fingertips are the most common injuries to the hand. Several million estimated visits to primary care providers and the emergency department occur each year. Lacerations to the fingers account for nearly half of non-work-related injuries.[6][7]

History and Physical

Patients present primarily with pain, inability to use the affected digit, or bleeding. Important points to elucidate are demographics (age, sex, occupation, and drug, tobacco, and alcohol use), hand dominance, involved digit, mechanism of injury, and previous medical and surgical conditions. Physical examination should be done in a controlled setting with appropriate lighting to allow for visualization of the injury and a proper assessment based on the history. Findings may reveal lacerations, closed or open fractures, and amputations of the tip.

Evaluation

Evaluation should include assessing for sensation, the range of motion at the interphalangeal joints, and capillary refill. X-rays of the affected digit and hand with two to three views are required.[8]

Consultation with a hand surgery service is required for the following:

1. Possible tendon injuries

2. Fractures (displaced or intra-articular)

3. Dislocations, such as open dislocation

4. Significant finger avulsion

5. Extensive laceration involving the proximal fold (eponychium)

6. Amputations with significant bone exposure

Treatment / Management

Primary goals of treatment include pain relief and attempting to reduce bleeding. Management is based on the type and severity of the injury.[1][9]

Subungual Hematoma

A subungual hematoma is due to a crushing injury. It occurs commonly from workplace accidents and presents as severe, throbbing pain with nail discoloration. It is due to a disruption of the blood vessels of the nail bed. A potential space exists between the nail plate and the underlying nail bed and matrix.

More than 50% of such injuries require trephination of the nail plate to allow decompression and drainage of the hematoma.

If it is associated with a fracture of the distal phalanx, examination of the nail bed is suggested, followed by immobilization using an aluminum splint until the patient has no further pain.

Nailbed Injuries

Nail and nail bed injuries include simple and complex lacerations, avulsion injuries, and amputations. Beware those nail bed injuries are usually associated with a partial or a complete fingertip avulsion.

Simple and complex lacerations should be approximated as best as possible while maintaining tissue integrity and cosmesis. In the pediatric population, absorbable sutures should be used, to mitigate the need for removal.

If there is associated partial nail avulsion or surrounding nail fold disruption, then nail removal is required. In general, when the nail bed is avulsed, it should always be repositioned, to obtain an anatomical reconstruction of the fingernail. Lacerations of the nail bed require blunt removal of the nail and primary closure of the nail bed with absorbable sutures. The nail should then be replaced to allow new nail growth, by maintaining the nail fold space. Beware that up to 50% of nail bed injuries may have an associated fracture of the distal phalanx. Avulsion injuries involving the nail bed have a poor prognosis.

Closed fractures which are minimally displaced can be splinted. If angulated or displaced, closed reduction is required displaced closed reduction is required with post-reduction films and outpatient follow-up. Unstable and intra-articular fractures necessitate evaluation by orthopedic or hand surgeons, as operative intervention is often required. Open fracture management includes a digital nerve block, irrigation, and soft tissue repair. This also will stabilize the fracture allowing for the aluminum splint placement. The patient should receive antibiotics, and close follow-up is needed either by a hand or an orthopedic surgeon.

Seymour Fractures (open physeal fracture of the distal phalanx)

Such fractures often occur through the cartilaginous growth plate. The insertion of the extensor tendon is proximal to the insertion of the flexor digitorum profundus. Fractures through the growth plate resulting in an extension of the proximal fragment and flexion of the distal fragment of the distal phalanx. These fractures are usually open and are associated with relatively high rates of infection as well as growth arrest. Seymour fractures may mimic mallet fingers at presentation; but, the displacement occurs through the fracture rather than the distal interphalangeal (DIP) joint.

Mallet Finger

The mechanism of injury, in this case, is a flexion force directed to an actively extended finger. The extensor tendon avulses a fragment of the epiphysis resulting in an intraarticular fracture that may also extend into the metaphysis of the distal phalanx.  It is recognized as a Salter-Harris Type III or Type IV fracture.

A mallet finger occurs due to the disruption of the extensor mechanism presenting as a flexion deformity since it results in the inability to extend the DIP joint. It is the most common tendon injury among athletes.

It can be classified as follows:

Type I tendon-only rupture

• Requires an immobilized DIP joint in continuous full extension for six to ten weeks

Type II small avulsion fracture

• Is similar to type I (if on x-ray, the splinted finger in extension is congruent with the rest of the non-injured articular surface of the distal phalanx on the distal articular surface of the middle phalanx)
• Surgical intervention is required if an open injury is present, and 30% to 50% articular fracture is involved.

Type III  more than 25% of the articular surface is involved

• This can be managed conservatively in most cases, except when associated with bony avulsion involving a third or more of the articular surface of the distal phalanx. At the opposite end of the spectrum is the flexor digitorum profundus avulsion, due to a forced extension of flexed finger. In this case, the patient presents with a finger in extension and unable to flex at DIP Joint. Operative intervention is warranted.

Swan-neck Deformity

It causes extension of the proximal interphalangeal (PIP) joint due to a dorsal displacement of lateral bands. Chronic untreated mallet finger results in this deformity.

Boutonnière Deformity

This causes extension of the DIP joint. The initial treatment includes immobilization of the PIP joint in continuous extension for five to six weeks, and hand surgery service follow-up.

Amputation

Amputations present a challenge in preserving function and restoring cosmesis. Non-operative management is indicated when there is no bone or tendon becomes exposed with less than 2 cm of skin loss. Operative primary closure can be performed if the exposed bone to be removed will not proximally compromise bony support to nail bed. Flap reconstruction is indicated when removal of bone will compromise nail bed support. Several flap techniques have been described for finger and thumb amputations. These include V-Y plasty, homodigital neurovascular island flap, and first dorsal metacarpal flap.

Secondary infections due to minor injuries such as a splinter, thorn, or nail-biting present either as a paronychia or felon. Paronychia involves the folds around the nail structures, and a felon abscess affects the fingertip pulp space. Pain, redness with a decreased movement of the affected digit are the most common manifestation. These entities require early evaluation, antibiotics, warm water or Betadine soaks, and possible incision and drainage when severe. 

Differential Diagnosis

• Base of thumb FX

• Digital collateral ligament injury

• Hook of hamate fracture

• MCP dislocations

• Metacarpal FX

• Pisiform fracture

• Phalanx dislocations

• Phalanx FX

• Scaphoid fracture

• Thumb collateral ligament injury

Complications

• Loss of nail
• Deformity of the finger
• Loss of the fingertip
• Paresthesias