Hand Infections

Factors Influencing Hand Infections

The clinical course of most hand infections is affected by anatomic, local, and systemic factors, in addition to bacterial virulence and the size of the inoculum. Anatomic factors that to some extent determine the ease of penetration, localization, and spread of infection include: (1) the thin layer of skin and subcutaneous tissue over the tendons, bones, and joints; (2) the closed space of the distal digital pulp; (3) the proximity of the flexor tendon sheath to bone and joint; (4) the proximal extent of the flexor sheath into the palm, connecting with the radial and ulnar bursae; and (5) the location of the thenar and midpalmar spaces in the hand and the space of Parona proximal to the wrist near the flexor tendon sheaths.

Local factors predisposing to infection include: (1) the extent and nature of soft-tissue damage, (2) the amount and virulence of bacterial contamination, and (3) the type and amount of foreign material present and persistent in the wound. Systemic factors relevant to the course of an infection involve ones that affect the immunocompetence of the patient. Examples include (1) malnutrition, (2) alcoholism, (3) intravenous drug abuse, (4) diabetes mellitus, (5) long-term use of corticosteroids and antitumor necrosis factor-α medicines, (6) immunosuppression following solid organ and bone marrow transplant, and (7) infection with human immunodeficiency virus.

Surgical site infections are uncommon after hand surgery. A database study that included 44,305 patients who had outpatient hand surgery procedures identified infections in fewer than 1%. Predictive factors were government-funded insurance and residence in a rural area; diabetes, obesity, and tobacco use were not associated with an increased risk of infection. The use of preoperative prophylactic antibiotics for small elective soft-tissue procedures, such as carpal tunnel or trigger finger release, remains an area of some debate; however, most agree that prophylactic antibiotics are not necessary for clean, elective procedures lasting less than 2 hours, even in patients with diabetes. A large study of clean, elective hand procedures based on 516,986 patients identified through an insurance claims database found no difference in the risk of postoperative infection in patients who received prophylactic antibiotics and those who did not. The overall 30-day surgical site infection rate was 1.5% in the antibiotic prophylaxis group and 1.4% in the group not receiving antibiotics. This finding applied to all clean soft-tissue hand procedures even after controlling for patient demographics, use of steroids or immunosuppressive agents, and comorbidities such as diabetes, HIV/AIDS, tobacco use, and obesity. With the rising use of wide-awake techniques for certain hand surgery procedures, attention has been given to infection risk in cases done outside the operating room under field sterility instead of full sterility characteristic of an operating room. One systematic review of six studies based on low-level evidence suggested that for some minor hand operations, such as carpal tunnel, trigger finger, or de Quervain release, undertaking the procedure outside the operating room may not alter the baseline infection rate.

Treatment of hand infections depends on the identification of the specific organism, the specific anatomic area involved in the hand and fingers, and the condition of the host whose comorbidities may influence treatment decisions. Identification of organisms with culture and antibiotic sensitivity studies allows proper medical treatment. Surgical procedures, including drainage of abscesses and debridement of necrotic tissues, also may be required.

General Approach to Hand Infections

With a careful history and physical examination, the location of the infection, the extent of spread, and the presence of swelling, lymphangitis, lymphadenitis, and joint involvement can be determined. Consideration should be given to other conditions that can be confused with infections, including gout, acute calcium deposition, pseudogout, pyogenic granuloma, insect bites, pyoderma gangrenosum, foreign bodies, factitious lesions, herpetic lesions, metastatic lesions, silicone synovitis, granuloma annulare, rheumatoid arthritis, nonspecific tenosynovitis, reactions to intravenous medications (e.g., chemotherapeutic agents), and Sweet syndrome, an aseptic neutrophilic dermatosis affecting the hand and resembling an infection. If the likelihood of infection is high, an attempt should be made to determine whether an abscess is present that requires drainage. Fluctuance can be difficult to identify in the hand. Radiographs are helpful in revealing bone injury. Radionuclide scanning may show bone infection, and MRI and ultrasound may localize an abscess. A complete blood cell count is obtained, along with determination of the serum C-reactive protein level and erythrocyte sedimentation rate. Strub et al. found significantly higher C-reactive protein levels in patients with infection “mimickers” (gout and pseudogout), and slightly fewer than half of patients with finger infections had elevated C-reactive protein levels. These authors concluded that the specificity of all inflammation markers (WBC, C-reactive protein, ESR) was inadequate for diagnosis. If any fluid or tissue is obtained, it is sent to the laboratory for Gram stain, crystals, culture, and antibiotic sensitivity determinations. Specific requests usually are made of the laboratory to culture for aerobic and anaerobic bacteria and for mycobacteria and fungi. In some cases, viral testing also can be helpful.

Initial antibiotic therapy traditionally has been empirical, depending on the results of the Gram stain and the most likely organism. Consideration should be given to the possibility of mixed flora as the cause of hand infections. Reviews of surgical infections of the hand and upper extremity have shown an increased incidence of gram-negative enteric and anaerobic organisms, even though the most common organisms were gram-positive aerobes (streptococcal species, Staphylococcus aureus, and coagulase-negative Staphylococcus ). Generally, the organism most commonly isolated from community-acquired hand infections is S. aureus. Methicillin-resistant S. aureus (MRSA) infections have had a rising incidence, especially in many urban medical centers. Typically, 80% or more of wounds cultured from swabs produce multiple organisms, whereas tissue specimens may produce a single causative organism in about 75%. Other organisms that commonly cause hand infections include streptococci, enterobacteria, Pseudomonas, enterococci, and Bacteroides. Less common causes include the various mycobacteria, gonococcus, Pasteurella multocida (in cat or dog bites), Eikenella corrodens (in human bites), Aeromonas hydrophila from standing fresh water (e.g., ditches, puddles, and ponds), Haemophilus influenzae (in children 2 months to 3 years old), a variety of anaerobic organisms (including clostridia), and other rare bacteria, such as those that cause anthrax, erysipeloid, and brucellosis. Postoperative or surgical site infections of the hand usually are caused by gram-positive organisms, including S. aureus and Staphylococcus epidermidis. Gram-negative organisms also may be isolated from surgical site infections. Overall, community-acquired MRSA has become the most common cause of culture-positive hand infections in the United States.

Antibiotics traditionally recommended for hand infections include a penicillinase-resistant penicillin or cephalosporin. When selecting antibiotics, it is important to be aware of the prevalence of antibiotic-resistant bacteria, such as MRSA. Vancomycin is effective against gram-positive organisms, whereas ciprofloxacin is most effective against gram-negative organisms. The addition of antibiotics effective against gram-negative organisms has been recommended for high-risk situations, such as infections in intravenous drug users and contaminated outdoor or farm injuries ( Table 79.1 ). Antibiotic options for outpatient coverage of community-acquired MRSA include clindamycin (although clindamycin resistance is increasing), trimethoprim-sulfamethoxazole, a tetracycline (doxycycline or minocycline), linezolid, and daptomycin. A recent study of 815 culture-positive hand infections over a 10-year period found clindamycin resistance to MRSA rising from 4% to 31% and levofloxacin resistance rising from 12% to 56% in the same study period (2005–2014). The authors suggested that clinicians should consider alternatives to the use of clindamycin, levofloxacin, penicillin, and other beta-lactam antibiotics, such as cephalosporins for treating common hand infections empirically, especially in urban centers.

Because of the constantly changing inventory of antibiotics and the variations in patient populations and wound flora, antibiotic selection should be based on a variety of considerations, including local antibiotic resistance information and the assistance of an infectious disease specialist when needed.

A protocol of early, aggressive surgical incision and drainage combined with intravenous antibiotic therapy should result in a shorter hospital stay, faster healing, and fewer complications. A randomized trial comparing cefazolin to vancomycin as a first-line agent in patients with community-acquired MRSA found no statistically significant differences in outcomes or cost of treatment. The authors emphasized the importance of early aggressive empiric antibiotic therapy with coverage for MRSA in all hand infections. Current recommendations for outpatient antibiotic treatment include amoxicillin and clavulanate plus trimethoprim and sulfamethoxazole. A comparison of patients who had differing antibiotic regimens after surgical treatment of simple hand infections (systemic cephalosporins and gentamicin bead chain, gentamicin bead chain alone, and no antibiotics) found no difference in outcomes, leading the authors to conclude that the use of antibiotics after surgical treatment of simple hand infection seems to be unnecessary.

Failure to recognize the polymicrobial nature of hand infections and inadequate surgical debridement are frequent causes of poor results. The importance of adequate surgical treatment cannot be overemphasized because antibiotics alone may be insufficient to control the infection.

Paronychia

A paronychia (“runaround”) infection usually is caused by the introduction of bacteria into the soft-tissue fold around the fingernail (eponychium) associated with a hangnail or poor nail hygiene ( Fig. 79.1 ). In three studies of paronychia, with a total of 61 patients, 25% were caused by anaerobic bacteria, 25% by aerobic bacteria, and 50% by mixed aerobic and anaerobic bacteria. Nonbacterial pathogens such as yeast and viruses also have been identified as causative organisms. The diagnosis is recognized by pain, redness, swelling, and possibly fluctuance at the paronychial and eponychial regions of the nail fold.

Initial treatment may include warm water or chlorhexidine soaks with or without topical or oral antibiotics. When an abscess is present, it should be drained. After drainage, antibiotics should be prescribed judiciously based on patient comorbidities and clinical judgment. A number of case studies have suggested that antibiotics are probably unnecessary in most cases. A prospective study of 46 acute fingertip infections treated with drainage and no antibiotics demonstrated only one recurrence attributed to inadequate resection. When an abscess forms in the eponychial or paronychial fold, it usually begins at one corner of the horny nail and travels under either the eponychium or the nail toward the opposite side. If an abscess is on one side only, it should be incised, angling the knife away from the nail to avoid cutting the nail bed, which would cause a ridge later. If the abscess is under one corner of the nail root, this corner should be removed. If it has already migrated to the opposite side and under the nail, a second incision should be made there, the skin folded back proximally, and the proximal one third of the nail excised. The wound is loosely packed with iodoform gauze for 48 hours for drainage ( Fig. 79.2 ).

Ogunlusi et al. described using the tip of a 21- or 23-gauge needle to lift the nail fold and drain the abscess; drainage was followed by oral antibiotic therapy. Resolution of acute paronychia occurred within 2 days in 8 of 10 patients. No anesthesia or daily dressing changes were required.

Infections caused by herpes simplex virus type 1 or 2 may be confused with bacterial paronychia. The “herpetic whitlow” is seen more often in health care workers and in immunocompromised patients and begins as a localized area of swelling with clear vesicle formation. Lymphangitis and lymphadenopathy may be present. The diagnosis can be confirmed with viral cultures of fluid from the vesicles, a Tzanck smear, and serum antibody titers. The condition is self-limiting, usually resolving over 3 to 4 weeks, and does not require surgical treatment. For immunocompromised patients, a course of an antiviral (acyclovir, valacyclovir, famciclovir, or foscarnet) can be used.

Felon

A felon is an abscess in the subcutaneous tissues of the distal pulp of a finger or thumb. The distal digital pulp is divided into tiny compartments by strong fibrous septa that traverse it from skin to bone. A transverse fibrous curtain also is present at the distal flexor finger crease. Because of these septa, any swelling causes immediate pain that is intensified because of increased pressure within the pulp. Infection can be caused by a penetrating injury from a foreign body or from “finger sticks” for medical reasons (e.g., hematocrit and blood glucose determinations). S. aureus is the organism most commonly isolated from fingertip infections. Swelling, redness, and pain, typical of cellulitis, are present initially. Abscess formation may follow rapidly. The pulp abscess (felon) can extend into the periosteum around the nail bed causing paronychia, or proximally through the fibrous curtain into the flexor sheath, leading to flexor tenosynovitis. Abscesses beginning deep, especially if untreated, penetrate the periosteum and cause osteomyelitis or a septic joint; the more superficial ones cause skin necrosis. Abscesses may form occasionally in the middle and proximal digital pulps.

Treatment generally consists of incision and drainage with antibiotics. Early presentation may be treatable with rest, elevation, warm soaks, and antibiotics. Because MRSA is becoming much more frequent, empiric treatment with antibiotics that cover MRSA is prudent until cultures dictate treatment. The diagnosis of an abscess in this area is sometimes difficult, but one usually is present if severe pain has lasted for 12 hours or longer.

Subfascial Space Infections

The potential spaces in the subfascial and deeper layers of the hand are infrequently infected ( Table 79.2 ). A high level of suspicion should lead to their detection and treatment. The recognized deep spaces of the hand include the interdigital web spaces, the midpalmar space, the thenar space, a less well-defined hypothenar space, the Parona space, and the dorsal subaponeurotic space ( Fig. 79.7 ).

Web Space Infection (Collar Button Abscess)

Web space infection usually localizes in one of the three fat-filled interdigital spaces just proximal to the superficial transverse ligament at the level of the metacarpophalangeal joints. The adjacent fingers often are held in an abducted position with the locus of swelling between them. Typically, the infection begins beneath palmar calluses in laborers. It may begin near the palmar surface, but because the skin and fascia here are less yielding, it may localize to drain dorsally. Here the tissue becomes obviously swollen, but the greater part of the abscess remains nearer the palm. This may be the more dangerous part because, unless drained, it may spread through the lumbrical canal into the middle palmar space. Two longitudinal incisions usually are necessary for drainage: one on the dorsal surface between the metacarpal heads and the other on the palm, beginning distal to the distal palmar crease and curving proximally. Crossing the palmar creases at right angles to the crease should be avoided ( Fig. 79.8 ). The web should not be incised.

Deep Fascial Space Infections

The palmar fascial space lies between the fascia covering the metacarpals and their contiguous muscles and the fascia dorsal to the flexor tendons. Its ulnar border is the fascia of the hypothenar muscles, and its radial border is the fascia of the adductor and other thenar muscles. This space is divided into a middle palmar space and a thenar space by a fascial membrane that passes obliquely from the third metacarpal shaft to the fascia of the palmar aponeurosis palmar to the flexor tendons of the index finger ( Fig. 79.9 ). The hypothenar space has as its boundaries: the hypothenar septum laterally, the fifth metacarpal dorsally, and the hypothenar muscle fascia medially and palmarly. The space of Parona is bordered by the pronator quadratus dorsally, the flexor pollicis longus laterally, the flexor carpi ulnaris medially, and the flexor tendons on the palmar aspect; it rarely is the site of abscess formation. Infections in these spaces are now rare because less extensive infections nearby usually are controlled by antibiotics before they spread. Abscesses in these spaces usually result from the spread of infection from other parts of the hand, typically from purulent flexor tenosynovial infections.

A middle palmar abscess can cause a severe systemic reaction, local pain and tenderness, inability to move the long and ring fingers actively because of pain, and generalized swelling of the hand and fingers, which resembles an inflated rubber glove. A thenar abscess causes similar symptoms, but the thumb web is more swollen, the index finger is held flexed, and active motion of the index finger and the thumb is impaired because of pain.