The fingertip is the most distal portion of the finger providing the tactile and sensory functions that are then relayed to the brain. It is anatomically defined as the portion of finger distal to the insertion of the flexor digitorum superficialis and extensor tendons on the distal phalanx, or the interphalangeal joint when referring to the thumb. The neurovascular supply of the fingertip is via digital arteries and nerves which trifurcate near the distal interphalangeal joint.
The volar pulp is supplied by specialized sensory Pacinian, Meissner corpuscles, and Merkel cells which provide detailed discrimination of touch and feel sensations. Fingerprints present on the volar surface comprise a uniquely individualized pattern formed by grooves and ridges. The dorsal surface consists of the nail fold, nail bed, and nail plate. Additional descriptions of the dorsal surface based on relationship to the nail are as follows: eponychium soft tissue just proximal to the nail, paronychium lateral nail folds, and hyponychium. The hyponychium is a plug of keratinous material situated beneath the distal edge of the nail where the nail bed meets the skin. The lunula white portion of the proximal nail demarcates the sterile area from the germinal matrix beneath. The nail bed is divided into the sterile matrix where the nail adheres, and the germinal matrix proximal to the sterile matrix; the latter is responsible for 90% of nail growth.
Fingertip injuries can be classified by the mechanism of injury or the level of injury based on the frequently used Allen classification system.The most common mechanisms seen include the following:
Allen classifications are based on the four types listed below.
Type 1 injuries may heal quite well by secondary intention. Type 3 and type 4 often require some flap coverage.
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 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.
Consultation with a hand surgery service is required for the following:
Fractures (displaced or intra-articular)
Dislocations, such as open dislocation
Significant finger avulsion
Extensive laceration involving the proximal fold (eponychium)
Amputations with significant bone exposure
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.
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.
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
Type II small avulsion fracture
Type III more than 25% of the articular surface is involved
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.
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.
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.
The majority of patients recover from injuries to the fingertips within weeks of treatment and close follow-up. Patient education should include prevention of subsequent or new injury to digits, as well as possible outcomes based on injury severity. Additional complications include a decrease in the function of the affected finger due to stiffness, as well as persistent pain or numbness.
The fingertip is a crucial part of the hand, and any injury can compromise function, as well as aesthetics. A multidisciplinary approach to fingertip injuries is essential to limit the morbidity. Since most patients with fingertip injuries present to the emergency department, the triage nurse should be aware of the importance of early referral of the patient to a hand surgeon, in case reimplantation is considered. While most injuries can be managed in the emergency department, some may require a referral to the plastic or orthopedic surgeon. The key is to preserve as much of the finger as possible. Once the injury is repaired, most patients require some type of finger rehabilitation to regain function, strength, and sensation. Patients should be educated on ways to protect the finger during the healing process, which can be several weeks or months. 
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