In 1939, Kanavel, author of the landmark Infections of the Hand, observed, "In almost all cases of serious infection the difficulty is to make a correct diagnosis both as to the nature of the infection and the position of the pus."[1] Specific infections covered in this article include paronychia, felon, herpetic whitlow, tenosynovitis, and deep fascial space infections. See the image below.
 View Image | A paronychia can progress to a felon if left untreated. |
Few structures of the body are as complex or as unique as the human hand with the functions of sensation, mobility, and strength in one small area. The hand consists of multiple compartments and planes, the knowledge of which allows one to understand the pathophysiology, diagnosis, and treatment of hand infections.
Infection of the area of the lateral nail fold (paronychium) is typically due to superficial trauma (eg, hangnails, nail biting, manicuring, finger sucking). Artificial nails have also been associated with acute paronychia. Although paronychia typically starts as a cellulitis, its progression to abscess formation is not uncommon. Infection that spreads to the proximal nail edge is termed an eponychia. Occasionally, infection can spread under the nail plate itself, resulting in a subungual abscess.
Chronic paronychia resembles acute paronychia but is usually nonsuppurative. People at risk include those repeatedly exposed to water and/or irritants as well as those who are immunocompromised. Metastatic cancer, subungual melanoma, and squamous cell cancer may rarely present as chronic paronychia.
The distal palmar phalanx is compartmentalized by tangentially oriented fibrous septa. These septa result in a closed compartment at the distal phalanx, which helps prevent the proximal spread of infection. Infection is typically due to direct inoculation of bacteria by penetrating trauma but may be caused by hematogenous spread and by local spread from an untreated paronychia.
Infection results in edema and increased pressure within the closed compartment. This, in turn, can impair venous outflow and lead to a local compartment syndrome and myonecrosis. Invasion of the bone leads to osteomyelitis.[2]
Herpes simplex virus (HSV) infection of the distal finger typically results from direct inoculation of the virus into broken skin. Type 1 and type 2 HSV infections are clinically indistinguishable. As in herpes infections elsewhere in the body, it is believed that the virus can remain dormant in the neural ganglia, leading to recurrent infections.[3] See the image below.
View Image | A herpetic whitlow. Image courtesy of Glen Vaughn, MD. |
Tendon sheaths consist of a visceral layer adherent to the tendon and a parietal layer. Notably, the flexor tendon sheath of the thumb is continuous with the radial bursae, whereas the flexor tendon sheath of the fifth digit is continuous with the ulnar bursae. In 80% of individuals, communication exists between the radial and ulnar bursae. The tenosynovial coverings of the second, third, and fourth digits do not communicate with either the radial bursae or the ulnar bursae in most individuals.
Infection within a flexor tendon sheath, as in other infections of the hand, usually is the result of direct inoculation of bacteria from penetrating trauma.
One common cause of penetrating trauma occurs when one person strikes another person in the mouth, resulting in a fight bite. A tooth may penetrate the metacarpophalangeal (MCP) joint capsule or an extensor tendon. Because the injury occurs while the joint is in flexion, deeper injuries to the extensor tendon or the MCP joint capsule or bone can be easily missed when the hand is examined in extension. For more information, see Bites, Human.
Infection can also occur by hematogenous spread, with Neisseria gonorrhoeae as the offending agent in many cases.
Pyogenic flexor tenosynovitis, an infection of the flexor tendon, is most common in the index, middle, and ring fingers and can form as early as 6 hours after the initial penetration.
Infection typically follows the course of the tendon sheath, which results in the spread of infection into the radial or ulnar bursae, depending on the primary tendon sheath involved. Elevated pressure within the tendon sheath due to infection may impair nutrient flow to the tendon. Tendon necrosis, impaired function, or both are disastrous sequelae of untreated elevated tendon sheath pressure.
The deep fascial spaces of the hand are potential spaces and consist of the dorsal subaponeurotic space, subfascial web space, midpalmar space, and thenar space. The dorsal subaponeurotic space lies volar (or deep) to the extensor tendons of the hand. The subfascial web space is contiguous with the dorsal subcutaneous space of the digits. The midpalmar space is demarcated by the palmar interosseous muscles dorsally and the flexor tendons of the third, fourth, and fifth digits ventrally. Lastly, the thenar space extends from the long metacarpal bone to the thenar eminence and consists of the area between the adductor pollicis muscle dorsally and the flexor tendon of the second digit ventrally.
These compartments are susceptible to infection by direct penetrating trauma, spread from a neighboring compartment, or hematogenous seeding. Because of the dorsal location of the lymphatics, erythema and swelling commonly appear over the dorsum of the hand, even when the injury is of palmar origin.
For more on hand anatomy, see Hand, Anatomy.
Infections of the hand (especially dominant-hand infections) can be devastating and frequently require admission for antibiotic therapy and/or surgical intervention. Possible complications are outlined below (see Complications).
Most resolve in 2-4 days.
Chronic infections are likely fungal infections and are typically more difficult to treat.
The prognosis is good, with healing in 1-2 weeks.
Infection usually resolves in 2-4 weeks.
Recurrence is not uncommon because virus may lay dormant in neural ganglia.
These have a fair prognosis, depending on the extent of tissue destruction, bony involvement, preexisting vascular insufficiency, and systemic complications (eg, bacteremia, sepsis).
Instruct patients on proper wound care including warm soaks, if indicated, and dressing changes.
Inform patients of the signs and/or symptoms of worsening infection, including increased pain, edema, redness, warmth, or fever.
Emphasize the importance of follow-up care and wound reevaluation with the primary medical doctor or the ED physician.
Instruct patients to avoid predisposing factors, such as nail biting, manicuring, and repeated exposure to water and/or irritants.[4]
For excellent patient education resources, visit eMedicineHealth's Infections Center. Also, see eMedicineHealth's patient education articles Paronychia (Nail Infection), Finger Infection, Hand Injuries, and Finger Injuries.
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The 4 cardinal signs, first described by Kanavel, include the following:
All 4 signs are possibly not present early in the course of infection. Patients may have associated lymphangitis, lymphadenopathy, and fever.
Deep fascial space infections all possibly present with lymphangitis (identified dorsally), lymphadenopathy, and fever.
Staphylococcus aureus and Streptococcus species are most common in acute cases.
Candida albicans (95%) and atypical mycobacteria are causes in chronic cases and in patients who are immunocompromised.
Anaerobes may be involved in the pediatric population secondary to finger sucking and children's playing in unhygienic spaces.
S aureus is the most common causative organism, but gram-negative organisms have been identified.
HSV-1 or HSV-2 is responsible.
S aureus and Streptococcus species are commonly isolated; however, some authors believe that N gonorrhoeae should be considered a possible pathogen until excluded by culture data.
Eikenella corrodens is observed in infections caused by human bites.
Pasteurella multocida and Capnocytophaga infections caused by cat and dog bites can progress rapidly to septic shock and death.
S aureus and Streptococcus species are most commonly isolated.
Organisms mentioned for infectious tenosynovitis also apply to deep space infections. This may be the result of local spread from infected neighboring tendon sheaths.
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These often require no laboratory tests because the diagnosis is made clinically.
The diagnosis can be confirmed by a Tzanck test, which demonstrates the presence of multinucleated giant cells in a scraping taken from the base of an unroofed vesicle.
As the infected spaces are drained and debrided in the operating room, preoperative laboratory tests (CBC count with differential; electrolytes; ECG, if age appropriate) may be requested by the hand surgeons and/or the anesthesiologist, but the diagnosis is made clinically.
Cultures are obtained in the operating room.
Because trauma is often a contributing factor in most hand infections, plain radiographs are useful in excluding fractures and retained foreign bodies if they are radiopaque.
Radiographs help identify subcutaneous or subfascial gas formation, if present.
Radiographs may reveal osteomyelitis.
In cases of severe infection causing vascular insufficiency, Doppler ultrasonography may assist in evaluation.
Bedside ultrasonography may also assist in differentiating among the various etiologies of hand infections by identifying fluid collections along tendon sheaths consistent with flexor tenosynovitis or "cobble-stone" patterns consistent with cellulitis.[6] Bedside ultrasonography is ideally performed using a water bath technique, which obviates the need for direct pressure of the ultrasound probe on the affected area while enhancing resolution.[7]
In acute paronychia, if no frank abscess or fluctuance is noted along the lateral nail edge, frequent hot soaks and possibly a short course of antibiotics may result in resolution of the infection.
If pus is present, drainage of the area is required. Using a No 11 scalpel blade held parallel to the nail, elevate the lateral nail fold at the site of the abscess to allow for drainage of pus. If a large amount of pus is expelled, a small wick is left in the incision to allow for continued drainage. If pus has tracked beneath the nail, the removal of an adjacent longitudinal section of the nail may be necessary to promote drainage. If a subungual abscess results in a floating nail, remove a portion of the nail or trephinate the nail to allow for complete drainage.
Elevation of the eponychial fold with a No 11 blade is quick, usually painless, and effective. If there is pain, it is extremely brief, less so than the pain of a digital block, so local anesthesia is typically unnecessary. Discuss the procedure with the patient to alleviate his or her fears. Extensive incision or penetration of the finger with the blade is unnecessary; simple elevation of the fold will do; therefore, no nerve block is needed. If the patient requests it, a digital nerve block can be performed for comfort.
After drainage and wick placement, dress the finger appropriately.
Update tetanus booster status as needed.
In chronic paronychia, treatment consists of avoiding predisposing factors and initiating topical steroids and antifungal agents.[8] Surgical intervention is indicated only if medical treatment fails. See the image below.
View Image | Paronychia incision and drainage. |
If frank abscess formation is present or the finger pad is tense, incision and drainage is indicated. This should not be undertaken lightly because improper placement of the incision can lead to scarring, sensory loss, unnecessary pain, instability of the finger pad, and spread of infection into the adjacent tendon sheath.
A longitudinal incision over the area of greatest fluctuance is the safest procedure when incision and drainage is required. Many other procedures, including hockey-stick or fish-mouth shaped incisions, are no longer recommended because of injury to neurovascular structure.
To avoid penetration of the tendon sheath, the incision should not extend to the distal interphalangeal crease. Using a hemostat, bluntly dissect the wound to promote drainage. Irrigate the cavity copiously and loosely pack with a gauze wick. After irrigation and loose packing of the wound, apply a dry gauze dressing and overlying splint. Update tetanus booster status as needed.
Apply a dry gauze dressing to the affected finger to prevent further spread of the lesion. Avoid incision or drainage of vesicles, which may lead to viremia and increase the risk for secondary bacterial infection. If secondary bacterial infection is suspected, treat appropriately with antibiotic therapy.[9] Antiviral agents, such as acyclovir, may shorten duration of symptoms if started within 48 hours of onset.[9, 10]
ED care consists of making the correct diagnosis, providing pain relief, initiating antibiotic therapy, elevating and immobilizing the hand, and consulting an experienced hand surgeon promptly for definitive treatment. Experienced surgeons in the operating room should perform the incision and drainage.
Prompt consultation with an experienced hand surgeon is indicated for patients with evidence of infectious tenosynovitis, deep fascial space infections, or osteomyelitis.
Cases of chronic paronychia that do not respond to initial therapy should be referred to a dermatologist.
All care should be taken to avoid manicures or other salon procedures with unclean implements. Proper hand hygiene should be observed.[11]
All wounds and abrasions to the hand should be taken seriously and thoroughly cleaned and dressed until healed. Careful observation and prompt medical evaluation prevents complications.
Instruct the patient with acute paronychia to soak the affected finger 3-5 times per day in warm water.
If a wick was placed, the patient usually can remove it easily after 24 hours if it has not fallen out already.
Schedule follow-up care with the primary care doctor or at the ED for 48 hours after initial incision.
Antibiotics, if prescribed, should be continued for 3-5 days.
In cases of chronic paronychia, topical steroids and antifungal agents should be initiated.
Pain medication may be prescribed as indicated.
Reevaluate the wound 48 hours after initial incision.
At this time, remove the packing and irrigate the wound.
If continued drainage is present, loosely repack the wound and schedule another follow-up appointment in 24 hours.
If no further drainage is present, repacking is unnecessary.
Instruct the patient to keep the wound clean by washing it twice daily with warm, soapy water followed by a clean gauze dressing.
The patient should continue antibiotics for 5-7 days.
Pain medication may be prescribed as indicated.
Instruct the patient to keep the affected area clean and covered with a dry dressing to prevent further transmission of the virus.
Oral acyclovir may be involved in preventing recurrence or in immunocompromised patients.
Pain medication may be prescribed as indicated.
Patients with evidence of infectious tenosynovitis or deep fascial space infections require inpatient treatment consisting of parenteral antibiotics and definitive incision and drainage by an experienced hand surgeon.
Inpatient splinting and occupational therapy for range of motion is essential to preserve function.
Emergency medicine physicians should feel competent and comfortable with the treatment of paronychia, felons, and herpetic whitlow.
Because of the specialized care required for infectious tenosynovitis and deep fascial space infections, transfer of patients with such infections may be necessary if those services are not available at the presenting hospital.
Prior to transfer, splint the affected area, update tetanus booster as needed, and initiate antibiotic therapy.
The goals of pharmacotherapy are to eradicate the infection and to prevent complications. With the rise of methicillin-resistant Staphylococcus aureus (MRSA) as a cause of hand infections, coverage with appropriate antibiotics is important.[12, 13] In this era, cephalexin alone is inappropriate coverage for hand infections, and coverage for all infections should include MRSA coverage.
Clinical Context: First-generation cephalosporin that inhibits bacterial growth by inhibiting bacterial cell wall synthesis. Bactericidal and effective against rapidly growing organisms forming cell walls. Primarily active against skin flora. Typically used for skin structure coverage and as prophylaxis in minor procedures. DOC for immunocompromised patients with paronychia.
Clinical Context: Lincosamide useful as treatment against serious skin and soft tissue infections caused by most staphylococcal strains. Also effective against aerobic and anaerobic streptococci, except enterococci. Inhibits bacterial protein synthesis by inhibiting peptide chain initiation at bacterial ribosome where it preferentially binds to 50S ribosomal subunit, causing bacterial growth inhibition. DOC for paronychia in children and those who wash dishes.
Clinical Context: Combination antimicrobial agent that uses a beta-lactamase inhibitor with ampicillin. Covers skin, enteric flora, and anaerobes. DOC for infectious tenosynovitis and deep fascial space infections.
Clinical Context: First-generation semisynthetic cephalosporin, which, by binding to 1 or more penicillin-binding proteins, arrests bacterial cell wall synthesis and inhibits bacterial growth. Primarily active against skin flora, including S aureus. Typically used alone for skin and skin-structure coverage. An alternate DOC for infectious tenosynovitis and deep fascial space infections.
Clinical Context: Potent antibiotic directed against gram-positive organisms and active against Enterococcus species. Useful in treatment of septicemia and skin structure infections. Indicated for patients who cannot receive or whose conditions have not responded to penicillins and cephalosporins or for those who have infections with resistant staphylococci. For abdominal penetrating injuries, combine with agent active against enteric flora and/or anaerobes. DOC (in conjunction with gentamicin) for infectious tenosynovitis and deep fascial space infections in patients who are allergic to penicillin. To avoid toxicity, current recommendation is to assay vancomycin trough levels after third dose drawn 0.5 h prior to next dosing. Use CrCl to adjust dose in patients with renal impairment.
Clinical Context: Aminoglycoside antibiotic used for gram-negative bacterial coverage. Used commonly in combination with both an agent against gram-positive organisms and an agent that covers anaerobes. DOC (in conjunction with vancomycin) for infectious tenosynovitis and deep fascial space infections in patients who are allergic to penicillin. Dosing regimens are numerous and are adjusted based on CrCl and changes in volume of distribution.
Therapy must cover all likely pathogens in the context of the clinical setting.
Clinical Context: Used to induce active immunity against tetanus in selected patients. Immunizing agents of choice for most adults and children >7 y are tetanus and diphtheria toxoids. Necessary to administer booster doses to maintain tetanus immunity throughout life.
Pregnant patients should receive only tetanus toxoid, not a diphtheria antigen-containing product.
In children and adults, may administer into deltoid or midlateral thigh muscles. In infants, preferred site of administration is mid thigh laterally.
Clinical Context: An adrenocorticosteroid derivative suitable for application to skin or external mucous membranes. Decreases inflammation by suppressing migration of polymorphonuclear leukocytes and reversing increased capillary permeability.
These agents are used in the treatment of chronic paronychia. They have anti-inflammatory properties and cause profound and varied metabolic effects. Corticosteroids modify the body's immune response to diverse stimuli.
Clinical Context: Broad-spectrum antifungal agent that inhibits yeast growth by altering cell membrane permeability, causing death of fungal cells. Reevaluate diagnosis if no clinical improvement after 4 wk.
A paronychia can progress to a felon if left untreated.
A herpetic whitlow. Image courtesy of Glen Vaughn, MD.
Paronychia incision and drainage.
A paronychia can progress to a felon if left untreated.
A herpetic whitlow. Image courtesy of Glen Vaughn, MD.
Paronychia incision and drainage.
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