I. Fingertip Infections
A. Paronychia (infection of the nail fold)
1. Acute paronychia
a. Etiology
i. Bacteria gain entry through a break in the seal between the nail fold and plate, often as a result of nail biting or manicures.
ii. Staphylococcus aureus is the usual pathogen.
b. Presentation and treatment
i. Early stage paronychia presents as swelling, erythema, and tenderness around the nail fold and can be effectively managed with warm soaks, antistaphylococcal antibiotics, and avoidance of nail biting.
ii. When the paronychia has progressed to abscess formation, drainage with removal of the involved portion of the nail plate from the fold is required.
iii. If the abscess cavity extends a significant distance from the nail fold, a separate dorsal counterincision may be needed over the eponychium.
2. Chronic paronychia
a. Characteristics
i. Represents a different disease process than acute paronychia
ii. Occurs in individuals whose hands experience daily prolonged exposure to water or wet environments (kitchen workers, housekeepers, etc)
iii. Candida albicans is frequently cultured from chronic paronychia.
b. Presentation
i. Common presentation is recurrent bouts of nail fold inflammation not as severe as an acute, fulminant paronychia. Over time, the edge of the nail fold becomes blunted and retracted.
ii. Abscess formation rarely occurs.
c. Treatment
i. Routine oral antibiotics usually are not effective.
ii. Eponychial marsupialization (removal of a 3-mm crescent of full-thickness dorsal tissue down to the level of the germinal matrix) is the recommended treatment. It should be allowed to heal by secondary intention. Results are thought to be superior when combined with nail plate removal.
B. Felon
1. Definition and etiology
a. Abscess of the volar pulp of the fingertip, usually occurring as a result of some penetrating injury (even as minor as a needle stick for blood glucose testing). The pulp consists of multiple small compartments of subcutaneous fat separated by fibrous septae between the distal phalanx and dermis.
b. As the abscess forms, swelling and pressure within these compartments increases, creating multiple "little compartment syndromes."
c. The resulting local vascular compromise promotes further necrosis and spread of the infection, perhaps resulting in infections of the distal phalanx, distal interphalangeal (DIP) joint, or flexor tendon sheath.
d. S aureus is the usual pathogen.
2. Treatment
a. Surgical drainage is the mainstay.
b. Drainage should be accomplished without violating the flexor sheath or DIP joint
c. A midaxial incision along the non-pressure-bearing side of the digit or a longitudinal incision over the volar pulp skin is preferred.
d. The wound is left open to allow drainage.
C. Herpetic whitlow
1. Characteristics
a. Viral infection that usually occurs on fingertips of children, dental workers, or respiratory therapists
b. Caused by the herpes simplex virus and is commonly mistaken for a bacterial paronychia or felon
2. Presentation
a. Early findings include mild erythema, swelling, and clear vesicles with intense burning pain that may seem disproportionate to that usually seen with a paronychia.
b. Over a 10- to 14-day period, the vesicles coalesce to form larger bullae, followed by crusting and superficial ulceration.
c. Viral shedding occurs throughout this period.
d. An uncomplicated infection in immunocompetent individuals usually resolves spontaneously within 3 to 4 weeks.
3. Treatment
a. Surgical drainage or debridement of herpetic whitlow lesions is contraindicated; bacterial superinfection, viral encephalitis, and death have been reported.
b. When administered early, oral acyclovir may lessen symptom severity.
c. In children, bacterial superinfection is not uncommon, and a 10-day course of a penicillinase-resistant oral antibiotic is required if cultures from blistering dactylitis reveal growth.
II. Septic Flexor Tenosynovitis
A. Etiology
1. Usual cause is direct penetration of the tendon sheath, but it may also result from direct spread from felon, septic joint, or deep-space infection.
2. Gram-positive cocci are common, but gram-negative and mixed flora are often seen in immunocompromised individuals.
B. Characteristics and presentation
1. Key physical examination findings (Kanavel signs):
a. Diffuse, fusiform swelling of the digit
b. Digit held in slight flexion
c. Tenderness to palpation of the flexor tendon sheath
d. Marked pain along the sheath with attempted passive digital extension
2. In many individuals, the thumb and small finger flexor sheath communicate through the radial and ulnar bursae at the wrist level; thus, direct spread of a flexor sheath infection from one digit to the other digit on the opposite side of the hand can occur through this space, resulting in a horseshoe-shaped abscess.
C. Treatment
1. Treatment is prompt irrigation of the flexor tendon sheath.
2. First-generation cephalosporin antibiotics are administered intravenously after intraoperative cultures have been collected.
3. More broad-spectrum coverage is recommended for diabetic or immunocompromised patients.
4. Upon clinical improvement following surgery, a 14-day course of antibiotic coverage is recommended.
5. If no improvement is evident within 24 to 48 hours following surgery, repeat debridement with extensile exposure should be considered.
6. Although patients do not commonly present within the first 24 to 48 hours of inoculation, intravenous antibiotics given during that time period have been reported to successfully resolve the infection nonsurgically. (This requires close monitoring—if no definitive clinical improvement is noted within 24 hours of initiating antibiotics, prompt surgical debridement is indicated.)
7. Presentations of chronic, more indolent swelling and pain over the flexor tendon sheath should raise suspicion for mycobacterial infection; intraoperative cultures for acid-fast bacilli and histopathologic examination for granulomas are indicated.
III. Septic Arthritis
A. Characteristics
1. Septic arthritis of the hand usually occurs from direct inoculation from penetrating trauma.
2. S aureus is the most commonly isolated organism.
3. Mixed flora are commonly seen in immunocompromised patients and in those whose joint sepsis is a result of a human or animal bite wound.
4. In sexually active individuals, gonococcal arthritis is a consideration.
5. Articular damage occurs as a result of bactericidal enzymes and immune complexes that lead to proteoglycan destruction. As chondrocytes are also disrupted, more proteolytic enzymes are released.
B. Diagnosis
1. Differential diagnoses include gout, pseudogout, psoriatic arthritis, rheumatoid arthritis, and Reiter's syndrome.
2. White blood cell (WBC) count is not elevated in all patients, but C-reactive protein (CRP) level and erythrocyte sedimentation rate (ESR) are consistently elevated.
3. Joint aspirate for fluid analysis is not always possible in proximal interphalangeal (PIP) and DIP joints due to small volume and difficult access. Synovial WBC >50,000/mm3 with polymorphonuclear leukocytes comprising more than 75% is indicative of bacterial infection.
C. Treatment
1. Surgical drainage is indicated in septic arthritis, although healthy patients presenting within 24 hours of symptoms or inoculation may be managed with intravenous antibiotics.
2. For PIP joint drainage, midaxial incision is preferred to avoid disruption of the central slip.
3. Dorsal midline incision is used for the metacarpophalangeal (MCP) joint and wrist.
4. Following 48 to 72 hours of intravenous antibiotics, a 10- to 14-day course of an oral antibiotic regimen specific to culture results is recommended.
5. Interphalangeal joint infections usually have a poorer outcome than do MCP or wrist infections after septic arthritis because residual stiffness is common.
6. Patients presenting more than 10 days after inoculation have poorer results.
IV. Osteomyelitis
A. Characteristics
1. Generally rare in the hand, representing <10% of all hand infections
2. Etiology is variable and includes open injuries, open or percutaneous fixation of fractures, hematogenous seeding, and spread from adjacent local infection.
3. S aureus is the most common infecting organism, followed by Staphylococcus epidermidis.
B. Diagnosis
1. WBC count elevation is not always present.
2. Elevated CRP level is more sensitive.
3. Radiographic changes may not be evident for 10 to 14 days.
4. Technetium Tc 99m bone scanning, indium-labeled bone scanning, and MRI may be able to detect osteomyelitis earlier and with greater accuracy.
C. Treatment
1. Acute osteomyelitis may respond to early intravenous antibiotic administration alone directed at suspected organisms.
2. If an implant is present, rifampin should be considered as a component to the antibiotic regimen because it is more effective against organisms adherent to implants.
3. The most reliable approach is biopsy and debridement of all infected and necrotic bone and soft tissue.
V. Human Bite Wounds
A. Etiology and presentation
1. The most common type of human bite wound to the hand is a clenched-fist injury resulting from striking another person in the mouth.
2. A common acute presentation is a small, short, innocuous-appearing transverse or jagged wound over the dorsal aspect of the MCP joint.
3. Patients may not disclose the true history, so a high degree of suspicion is needed.
4. Over time, pain, swelling, erythema, and purulence occur, which are often what lead to the patient presenting for care.
5. After the tooth has penetrated the MCP joint, bacteria become trapped because of the change in alignment of the capsule, extensor tendon, and skin as the fist is released. (Extensor tendon lacerations may retract proximal to the cutaneous wound and can therefore be missed.)
6. Radiographs should be obtained to assess for a fracture or broken tooth fragment in the wound.
7. S aureus and Streptococcus are the most common culture isolates in human bite wounds.
8. Eikenella corrodens and other gram-negative organisms are also common pathogens.
B. Treatment
1. Surgical debridement of the wound and joint capsule is indicated. The wound is left open for drainage.
2. Intravenous antibiotic therapy should target Staphylococcus, Streptococcus, and gram-negative organisms.
VI. Animal Bite Wounds
A. Dog and cat bites
1. Dog bites are by far the most common animal bites in the United States.
2. Cat bites become infected more frequently than do dog bites because the cat's needle-like teeth can cause a deep puncture wound. Therefore, a high suspicion for penetration into joints and flexor tendon sheaths is recommended with cat bites.
3. Common pathogens cultured from dog and cat bites are S aureus, Streptococcus, Bacteroides, and Pasteurella multocida. Pasteurella is more commonly isolated from cat bite wounds; it occurs in 80% of individuals with cat bites.
4. Antibiotic therapy should be targeted at gram-positive, gram-negative, and anaerobic organisms.
5. Treatment
a. Thorough cleansing of wounds with soap or iodine has been shown to dramatically reduce the development of rabies in those bitten by infected animals.
b. In cases of bites from animals with suspected rabies, human diploid cell rabies vaccine and human rabies immunoglobulin is administered.
C. Marine infections
1. Acute infections from marine injuries are often caused by Staphylococcus, Streptococcus, Pseudomonas, and Enterobacter species.
2. Chronic infection manifested may be caused by Mycobacterium marinum, often resulting from minor injuries incurred while cleaning aquariums. M marinum may present as a chronic flexor tenosynovitis.
D. Infection resulting from leech therapy
1. Leech therapy, which often is used to assist with venous drainage after limb replantation or microvascular free-tissue transfer, can result in infection from Aeromonas hydrophilia, which can cause abscess formation, sepsis, and endocarditis.
2. During leech therapy, antibiotic coverage is recommended against gram-negative organisms.
VII. Deep-Space Infections
A. Definition—The deep palmar spaces of the hand include the thenar, hypothenar, and midpalmar spaces. The thenar and midpalmar spaces are separated by a fascial septum running between the palmar aspect of the third metacarpal and the palmar fascia.
B. Presentation—Thenar and midpalmar space infections typically present as profound palmar swelling with loss of palmar concavity. The thenar space is the most commonly infected.
C. Treatment—All deep-space infections require surgical debridement and intravenous antibiotic therapy.
VIII. Uncommon Infections
A. Mycobacterial infection
1. Both tuberculous and atypical mycobacterial infections exhibit similar clinical findings and are clinically indistinguishable.
2. Chronic dactylitis, tenosynovitis, arthritis, and osteomyelitis are features of both conditions.
3. Biopsy for histopathology and microbiology is paramount because drug therapy and prognosis is different for each condition.
4. Mycobacterium tuberculosis
a. Evidenced by a tuberculous caseating granuloma on histopathology specimen.
b. Culture on Lowenstein-Jensen (L-J) medium at room temperature and send stain for acid-fast bacilli.
c. Culture growth is slow (may take weeks), so chemotherapy may begin empirically with rifampin, isoniazid, and a third agent such as pyrizinamide; if positive, chemotherapy should continue for at least 9 months.
d. Surgical treatment in the form of tenosynovectomy or deep-tissue debridement is usually necessary.
5. Atypical mycobacteria are all mycobacteria other than tuberculosis.
a. M marinum and M avium-intracellulare are most common.
b. M marinum often results from injuries in marine environments, including aquariums.
i. Culture requires incubation on L-J agar at 30° to 32° (lower temperature than required for M tuberculosis).
ii. Antimicrobial therapy consists of ethambutol, rifampin, or clarithromycin.
c. M avium is the second most common atypical mycobacterial infection and is more commonly seen in patients with acquired immune deficiency syndrome (AIDS).
i. Can also occur in the absence of human immunodeficiency virus (HIV) infection
ii. Culture is also on L-J agar, but at room temperature.
6. M leprae (Hansen disease)
a. Spread by human-to-human contact (probably by nasal droplets) as well as by contact with infected southwestern armadillos.
b. Chronic infection of the peripheral nerves
c. In the upper limb, the ulnar nerve is most commonly affected.
d. With increasing degree of peripheral nerve dysfunction, sensory loss is often the presenting symptom.
e. Treatment is with dapsone, with or without rifampin.
i. If treated early, it can be cured.
ii. Late treatment usually results in irreversible nerve damage followed by digital autoamputation.
B. Anthrax
1. Caused by spores from facultative gram-negative anaerobe Bacillus anthracis, found in top layers of soil
2. Found in cutaneous, gastrointestinal, and inhalational forms
a. Cutaneous form starts as small, painless, enlarging red macula that progresses to a papule over a few days; this ruptures, ulcerates, and becomes a black eschar
b. Should be cultured for anthrax bacilli
c. With its spread, patient develops regional lymphadenopathy, fever, and chills.
3. Intravenous antibiotic therapy against gram-negative rods should be initiated to sterilize the ulcer.
a. Penicillin, quinolones, or doxycycline are reasonable choices.
b. After signs of clinical improvement, patient may be switched to a 2-month course of oral antibiotics.
C. Fungal infections
1. Characteristics
a. Cutaneous fungal infections, known as keratinophylic fungi, dermatophytes, or tinea, are quite common but rarely present to the hand or upper extremity surgeon.
b. Often resolve spontaneously within weeks or months
c. Candidal infections may also occur in macerated areas and will often respond to keeping the affected area dry and to topical antifungal agents.
2. Onychomycosis (fungal infection of the nail)
a. May occur along the distal, proximal, or lateral margin of the nail plate, depending on site of entry
b. Trichophyton rubrum and Candida are the most frequently isolated organisms.
c. Greater treatment success has been noted when systemic anifungals are combined with nail plate removal.
3. Sporothrix schenckii
a. Common soil organism; spores get implanted from subcutaneous penetration (eg, a rose bush thorn)
b. Sporotrichosis is a subcutaneous-level infection manifested by local ulceration along with proximal enlargement of lymph nodes.
c. S schenckii should be isolated on Sabouraud dextrose agar at room temperature.
d. Oral itraconazole for 3 to 6 months has supplanted potassium iodide as the standard treatment, because potassium iodide is associated with skin rashes, thyroid dysfunction, and gastrointestinal problems.
4. Histoplasmosis
a. Caused by Histoplasma capsulatum
b. Endemic to the Ohio and Mississippi River valleys
c. Usually a subclinical systemic infection manifested only by findings on chest radiographs and by positive skin testing
d. Upper extremity involvement can occur as localized tenosynovitis.
e. Treatment is tenosynovectomy and amphotericin B.
5. Coccidiomycosis
a. Generally occurs in arid regions of the southwestern United States and northern Mexico
b. Common pulmonary involvement is usually subclinical.
c. Upper limb findings include synovitis, arthritis, or periarticular osteomyelitis.
d. Treatment is surgical debridement and amphotericin B.
IX. Conditions Often Mistaken for Infections
A. Pyoderma gangrenosum
1. Painful, enlarging, ulcerative skin lesion usually seen in patients with coexisting systemic disease—rheumatoid arthritis, inflammatory bowel disease (especially ulcerative colitis), polyarteritis nodosa, or diabetes mellitus.
2. Treatment is nonsurgical.
B. Pyogenic granuloma
1. Appears as a protuberant, red, granulomatous mass, usually palmar, that is friable and bleeds easily.
2. The lesion often occurs after a penetrating injury or repeated local irritation.
3. Treatment is silver nitrate or surgical excision.
C. Rheumatoid arthritis
1. Can present as articular swelling, tenosynovitis, or as subcutaneous nodules that resemble chronic or acute infections.
2. Joint aspirate can help distinguish inflammatory arthritis from joint sepsis.
3. Biopsy and culture of persistent tenosynovitis of questionable etiology can be performed.
D. Brown recluse spider bite
1. Often not painful when inflicted; many patients do not even recall the incident
2. The initial appearance is as a slightly raised, reddened mass that slowly spreads and exhibits central necrosis.
3. The central necrotic portion can become infected and require surgical debridement.
E. Acute gout
1. Can resemble a septic joint
2. White, toothpaste-like appearance of tophus aspirate may reveal monosodium urate crystals, which appear as negatively birefringent crystals under polarized microscopy.
3. Bacterial superinfection may occur, requiring antibiotic coverage.
4. Treatment of an acute joint inflammation from gout is largely nonsurgical, consisting of anti-inflammatory medication and occasionally colchicine.
F. Metastatic or primary tumors
1. Can have the appearance of chronic infections
2. Squamous cell carcinoma, melanoma, and basal cell carcinoma are particular malignant lesions that must not be missed, supporting the caveat "culture all tumors and biopsy all infections."
X. Immunocompromised Patients
A. Diabetes mellitus
1. Most common form of systemic vulnerability to infection seen in the US population.
2. Patients are more vulnerable to infection and generally incur greater morbidity from a given infection than immunocompetent individuals.
3. Lymphocyte dysfunction and a hyperglycemic environment that nurtures bacterial proliferation may contribute.
4. Patients with renal failure are especially vulnerable to complicated infections.
5. Infections in the diabetic population are more frequently polymicrobial and more often result in amputation.
B. Transplant patients are prone to spontaneous hand infections, often atypical, which require surgical debridement and aggressive antibiotic or antifungal regimens.
C. Patients with HIV
1. Susceptible to upper limb infections similar to those seen in the diabetic population.
2. Patients in whom HIV has progressed to AIDS have a higher infection rate.
3. The true effect of merely being HIV-positive remains undetermined; the higher infection rate may be a reflection of a significant portion of HIV-positive patients using intravenous drugs without sterile technique rather than any actual effect from the virus itself.
XI. Drug Principles
A. Vancomycin
1. Effective against methicillin-resistant S aureus (MRSA), but offers no gram-negative coverage
2. If infused too quickly, can cause red man syndrome
B. First-generation cephalosporins (cephalexin, cefazolin) are recommended as prophylaxis against wound infections.
C. Aminoglycosides are effective against gram-negative organisms, including Pseudomonas, but levels must be followed to avoid nephrotoxicity (reversible) and ototoxicity (irreversible).
D. Tetracyclines are contraindicated in children younger than 8 years because they can cause tooth discoloration.
E. Terbanifine is drug of choice for onychomycosis.
Top Testing Facts
1. Chronic paronychia is treated by eponychial marsupialization.
2. A common culture in chronic paronychia is C albicans.
3. In early herpetic whitlow, the vesicles coalesce to form larger bullae over a 10- to 14-day period, followed by crusting and superficial ulceration; viral shedding occurs throughout this period.
4. Elevated CRP level is more sensitive than elevated WBC count in the diagnosis of osteomyelitis of the hand.
5. Eikenella corrodens, a gram-negative organism, is a common pathogen in human bites.
6. Pasteurella infection occurs in 80% of individuals with cat bites.
7. Culture of atypical mycobacterial species requires incubation on L-J agar at 30° to 32°, a temperature lower than that required for tuberculosis culture.
8. S schenckii should be isolated on Sabouraud dextrose agar at room temperature. Oral itraconazole for 3 to 6 months has supplanted potassium iodide as the standard treatment.
9. Aminoglycoside nephrotoxicity is reversible; ototoxicity is not.
10. Tetracycline is contraindicated in children younger than 8 years because of tooth discoloration.
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