Hand Infections: Epidemiology and Public Health Burdens

Introduction

Hand infections and their sequelae are a significant public health burden worldwide. Even when treated appropriately, infections can result in scarring, joint contractures, stiffness, and chronic pain. Although the field of hand surgery has evolved over the last century, infections of the hand, their causes, and treatments remain largely unchanged. Prompt diagnosis, surgical debridement, and antibiotic coverage remain the standard of care. As medical treatments for complex diseases improve, patients with chronic diseases are surviving longer. Identification of infection in immunosuppressed patients can be difficult because typical signs and symptoms are often lacking. Public health problems such as intravenous drug use lead to new challenges in treating patients with acute hand infections. The purpose of this article is to review the epidemiology and social impact of upper extremity infections.

History:

Acute Phlegmons of the Hand, published in 1905 by Dr. Allen Kanavel, was one of the first anatomic studies of the hand. Dr. Kanavel (1874–1938) worked as a general surgeon in Chicago, IL and cared for many patients with hand infections. Through repetition, he noticed predictable patterns. Using anatomic cross-sectioning and plaster-of-Paris injection studies, he defined the “five great spaces” of the hand: dorsal subcutaneous, dorsal subaponeurotic, hypothenar, thenar, and middle palmar spaces.¹ Kanavel’s work culminated with the publication of Infections of the Hand in 1912, in which he systematically describes various infections and their management. (IMAGE 1)

Figure 1:

(A) A radiographic plate published by Dr Kanavel, demonstrating the middle palmar space following plaster-of-Paris injection. (B) A subsequent high-pressure injection, demonstrating the ability of purulent infections to expand into adjacent compartments under pressure. (Courtesy of GalterHealth Sciences Library & Learning Center, Northwestern University Feinberg School of Medicine, Chicago, IL, USA.)

Epidemiology

Data on the overall epidemiology of hand infections are scarce. Unique injury data, such as the characteristics of domestic animal bites, are more frequently reported. Most studies are published out of urban hospitals in large metropolitan areas. Patients treated in primary care facilities or in rural areas likely represent a large portion of injuries and often go unaccounted.

Incidence

Two-thirds of hand infections occur in men, with an average age of 40 years of age. Over one third of hand infections are the result of trauma.² Domestic dog bites account for over 800,000 health care visits in the U.S. annually. Cat bites are less common (estimated 400,000 per year in the U.S.) but more likely to cause infection – nearly half of all cat bites become infected without treatment.^3,4 Dogs have blunt teeth that leave an open wound that can drain, whereas cats’ teeth are sharp allowing them to inject a bolus of bacteria into the deeper tissue. Two-thirds of pet bites affect the upper extremity.^5,6

Post-operative surgical site infections are rare in hand surgery - 1.7 per 1,000 procedures. Approximately 10% of patients with a surgical site infection require a secondary procedure.⁷ Most infections are effectively treated with oral antibiotics.

Morbidity and Sequelae

Infections of the hand can lead to loss of function and disability, even when treated promptly. Infections of the flexor or extensor tendon spaces can lead to tendon necrosis, adhesions, and chronic stiffness. Intraarticular infections in the digits or carpus often cause progressive arthritis and require a salvage operation. Severe deep space infections and necrotizing fasciitis result in extensive soft tissue damage which sometimes requires flap coverage or amputation.

Microbiology & Antibacterial Resistance:

Staphylococcus Aureus, a round gram-positive bacilli, is the most common cause of hand infections.⁸ In most areas of the U.S., community acquired methicillin-resistant Staphylococcus Aureus (CA-MRSA) is the most common strain with culture rates approaching 50%.^9,10 Beta-hemolytic streptococcus, another round gram-positive bacteria, is the second most common cause of common hand infections. A causative organism cannot be identified in one of every 10 infections.²

Penicillin became available in 1929,¹¹ and soon after, there were discoveries of penicillin resistance in Staph Aureus. By 1955, over 70% of Staphylococcus cultures were penicillin resistant.¹² Currently, with the frequent use of broad spectrum antibiotics, the rate of multi-drug resistant organisms specific to hand infections has increased. Resistance has been demonstrated to Methicillin in 46% of cases, Clindamycin in 31% of cases, and Levofloxacin in 56% of cases.¹³

Economic Impact

The cost of treating hand infections varies widely. A course of outpatient antibiotics is relatively inexpensive; however, surgery, maintenance of indwelling intravenous (IV) catheters, and IV treatments can be significantly more costly. In addition, many patients with hand infections are needlessly transferred to tertiary centers for care that can be provided at lower level hospitals and clinics.¹⁴ The cost of treating dog and cat bites ranges from $1,880 to $82,000.¹⁵ Little has been published on the cost of post-operative infections in hand surgery. A Veterans’ Affairs study found that patients who developed superficial surgical site infections incur a 1.25 times greater expense, whereas deep surgical site infections involving muscle or implants cost 1.93 times more.¹⁶

Risk Factors & Comorbidities

Although many hand infections result from trauma², several risk factors predispose individuals to infection. This section presents common risk factors for upper extremity infection and their unique characteristics.

Diabetes

Type 2 Diabetes Mellitus (DMT2) is the most prevalent, modifiable, chronic illness in the U.S. The CDC estimates that 30.3 million people are diabetic, 7.2 million of whom are undiagnosed.¹⁷ Diabetes is a risk factor for several common hand conditions such as carpal tunnel syndrome and trigger finger.¹⁸ Diabetic patients are at increased risk of idiopathic and post-operative infection and are more likely to require operative intervention for infection.^19,20,21 Hand surgeons must have increased suspicion for atypical hand infections – fungus and rare species are more common in this population.²²

Human Immunodeficiency Virus

The CDC estimates that 1.1 million adults are infected with human immunodeficiency virus (HIV) in the U.S.²³ Patients with HIV have progressive failure of their immune system which allows opportunistic infections to thrive. They have a higher rate of severe, necrotizing infection and more frequently require aggressive surgical debridement.^24,25

Immunosuppression

Patients who are pharmacologically immunosuppressed for organ transplants, autoimmune disorders, and other medical conditions are at increased risk for infection. Deep space infection and osteomyelitis are far more common in these patients than in the general population.²⁶

Hand surgeons often treat rheumatoid patients and must be knowledgeable on anti-rheumatic drugs. Traditional disease-modifying anti-rheumatic drugs (DMARDs) such as methotrexate do not increase infection risk.²⁷ Patients may continue methotrexate in the peri-operative period. Biologic DMARDs antagonize IL-1, IL-6, or TNF-alpha. Anti-TNF-alpha medications increase the risk of skin and soft-tissue infection in a dose-dependent manner.^28,29 Clinical guidelines for managing biologic DMARDs at the time of surgery do not yet exist. Patients, rheumatologists, and surgeons must work together to devise a medication plan based on individual needs and risks.

Intravenous Drug Use

It is estimated that one million people are active IV drug users (IVDU) in the United States.³⁰ IVDU is one of the strongest risk factors for Community Acquired MRSA infection and necrotizing fasciitis. ^31,32 Patients with poor vein access often turn to subcutaneous injection (known as “skin popping”) which has the highest risk of infection amongst drug administration methods.³³ Although a difficult patient population to treat, it is important to recognize and refer IVDUs to social work and addiction services in an attempt to reduce future health problems. Low-cost educational programs significantly reduce unsafe injecting practices and reduce injection site complications by 27% compared to controls.³⁴

Occupation

Some professions predispose individuals to atypical infections. Examples include:

• Veterinarians and animal workers

  • Pasteurella Multocida – An anaerobic, gram-negative coccobacilli that is regularly part of the normal bacterial flora within the oropharynx of animals – most commonly domestic cats and dogs. It leads to purulent hand infections following animal bites. Amoxicillin plus a beta-lactam inhibitor is the treatment of choice.³⁵

• Aquarists or fisherman

  • Mycobacterium Marinum – Results in Aquarium Granuloma, an erythematous nodule/s that ulcerates as it matures. A history of working with aquariums or with aquatic species is common. Multi-drug antibacterial therapy is frequently required for treatment.³⁶

  • (IMAGE 2)

• Horticulturists

  • Sporothrix schenskii – Sporotrichosis, commonly known as rose gardner’s disease, is a fungal infection. It most commonly affects cutaneous tissue through direct inoculation when the skin is punctured by plant material (rose thorns, hay, sphagnum moss). Treatment consists of 3–6 months of Itraconazole therapy.³⁷

• Dentists

  • Herpes Simplex Virus – Also known as Herpetic Whitlow. This is the result of direct inoculation of the cutaneous tissue of the fingers/thumb. Presents most commonly as an acute, painful episode with swelling and erythema of the distal digit, with subsequent formation of clear fluid-filled vesicles. The disease is self-limiting, and surgical debridement is not recommended as it can disseminate the underlying infection.³⁸

  • (IMAGE 3)

Figure 2:

A violet-colored, raised, verrucous lesion overlying the dorsal fourth and fifth metacarpophalangeal joints, demonstrating a typical appearance of Aquarium Granuloma. Cutaneous lesions surrounding joints as seen here can lead to stiffness and contracture. Surgical debridement may be necessary for large, necrotic wounds.

(From Wu TS, Chiu CH, Yang CH, et al. Fish Tank Granuloma Caused by Mycobacterium marinum. PLoSOne 2012; 7(7): e41296; with permission.)

Figure 3:

Mycobacterial infection of the volar hand. The arrow demonstrates rice bodies exiting an incision decompressing the carpal tunnel and middle palmar space. Rice bodies can become space-occupying lesions within the carpal tunnel, leading to an acutely developing carpal tunnel syndrome.

Regional

Globally, purulent hand infections are most commonly the result of Staph. Aureus; however, there are unique infections that are native to areas of Africa, Asia, and South America. Some of these soft tissue infections can manifest months to years after initial exposure, and even brief travel to endemic areas can predispose individuals. Recent or historical travel to exotic locations should be clarified in all patients with atypical appearing infections.

• Tuberculosis

  • Caused most commonly by Mycobacterium Tuberculosis. Manifestations are not commonly seen within the hand – occurring in only 10% of musculoskeletal infections. Within the hand it most commonly presents as tenosynovitis or osteomyelitis. Surgical debridement usually reveals the classic “Rice Bodies” - outpouchings of synovial membrane containing tuberculoid material.³⁹

  • (IMAGE 4)

• Buruli Ulcer

  • The result of Mycbacterium Ulcerans, an acid-fast bacteria. Up to 5,000 people are affected globally per year, mostly in Central and West Africa, Australia, and tropical South America. 1/3^rd of cases affect the upper extremity. Initial presentation is a benign and painless nodule or area of swelling that begins to ulcerate within 3–4 weeks. Mycolactone is a toxin produced by M. Ulcerans, which is the main cause of soft-tissue destruction. Diagnosis is traditionally performed through tissue swab/cultures, but can take up to 8 weeks. PCR testing exists for diagnosis, but is commonly unavailable in endemic areas. ⁴⁰

  • (IMAGE 5)

• Leishmaniasis

  • The result of one of more than a dozen known protozoa the Leishmania family, subcategorized into New World vs Old World species. The disease is spread through the bites of sandflies, and affects up to 1 million individuals per year. Cutaneous Leischmaniasis is the most common form of the disease, which slowly develops over weeks to months after initial exposure. The lesions are usually raised papules or ulcerations, and are frequently painless.⁴¹

  • (IMAGE 6)

• Yaws

  • A historically common cutaneous infection caused by Treponema Pallidum Pertenue. Spread through direct contact of infected wounds, it most commonly affects children under the age of 18. Yaws presents initially as a single papilloma that will eventually ulcerate. Left untreated the disease will progress to a secondary form, which presents with diffuse yellow lesions on the extremities, and desquamation of the palms and feet. Treatment is accomplished by a single dose of penicillin or azithromycin.⁴²

  • (IMAGE 7)

Figure 4:

A Buruli ulcer of the dorsal forearm and hand. Note the granular-appearing tissue at the base of the ulcer, suggesting a more chronic infection. Erythema extending distally into the dorsal hand from the large ulceration demonstrates the expanding nature of Buruli ulcers. Left untreated, Buruli ulcer in the hand and forearm can lead to extensor and flexor tendon disruption. (From YerramilliA, Tay EL, Stewardson AJ, et al. The location of Australian Buruli ulcer lesions—Implications for unravelling disease transmission. PLoSNeglected Tropical Diseases 2017;11(8):e0005800; with permission.)

Figure 5:

Cutaneous Leishmaniasis resulting in a large dorsal hand lesion with deep central ulceration and hyperkeratotic, heaped and raised borders. Although wounds can be quite extensive, surgical debridement is often unnecessary, as the wounds frequently heal with medical management. (Courtesy of Centers for Disease Control and Prevention (CDC) and D.S. Martin.

Figure 6:

(A) Loss of palmar epithelium is commonly seen in secondary and tertiary Yaws. (B) Yellow papillomasand ulcers of the proximal dorsal forearm; the arrow marks a likely “mother” lesion, with surrounding daughter lesions. Initially these lesions may be painless, but can become painful over time. (Courtesy of [A] Centers for Disease Control and Prevention (CDC) and S. Lindsley; and [B] Centers for Disease Control and Prevention (CDC) and P. Perine.)

Diagnosis and Management of Hand Infections

Diagnosis

All encounters should begin with a complete medical history and hand examination. Clarify the mechanism of injury, duration of symptoms, and any treatment to date. Occupation, hobbies, and recent exposures may guide diagnosis. Tetanus vaccination status should be verified in any patient with an open trauma or bite injury. Tetanus immunoglobulin and toxoid should be administered to patients who are not up to date on boosters.

An individual with MRSA who has not been exposed to a healthcare facility within the last year is assumed to have Community-Acquired MRSA. Making this distinction is important, as CA-MRSA is known to carry a unique gene sequence coding for Panton-Valentine leucocidin – a toxin that can increase local soft-tissue damage.⁴³

Infectious symptoms such as fevers and chills are often absent in patients with hand infections. Likewise, initial laboratory evaluation of white blood cell count, erythrocyte sedimentation rate, and C-reactive protein are frequently normal.² Diagnosis is largely clinical, based on the predictable presentations and patterns of infections.

Necrotizing fasciitis should be considered in all patients with rapid change in clinical exam. Progression of erythema, tense swelling (peau d’orange skin), and pain out of proportion with the exam should raise suspicion. Necrotizing fasciitis is a clinical diagnosis, but a basic metabolic panel and complete blood count are useful for calculating a LRINEC (Laboratory Risk Indicator for Necrotizing Fasciitis) score. (TABLE 1) A score greater than 6 has been shown to have a 92% positive predictive value and 96% negative predictive value.⁴⁴

Table 1:

LRINEC Scoring system.

Laboratory Parameter	Value	Points
CRP (mg/dL)	<15	0
	≥15	4
WBC (per mm3)	<15	0
	15–25	1
	>25	2
Hemoglobin (g/dL)	>13.5	0
	11–13.5	1
	<11	2
Sodium (mEq/L)	≥135	0
	<135	2
Creatinine (mg/dL)	≤1.6	0
	>1.6	2
Glucose (mg/dL)	≤180	0
	>180	1

Radiographs are obtained to rule out fracture and retained foreign bodies. Ultrasound can be helpful to diagnose fluid collections, radiolucent foreign bodies, and joint effusions.^45,46 MRI with and without contrast is valuable in diagnosis of deep space infection, foreign bodies, and differentiation between soft-tissue edema vs fluid collections.

Management Principles

Purulent infections, such as felons, abscesses, and paronychia, are treated with debridement and antibiotics. When possible, cultures should be sent before antibiotics are given. Incisions should be placed directly over the area of maximum fluctuance and should be large enough for easy access to and complete drainage of the infection. Longitudinal incisions allow for extension proximally and distally if needed but should not cross flexion creases perpendicularly. All necrotic tissue must be debrided. Blunt dissection can be used to release areas of loculation. Wounds should be left open, packed with gauze to prevent premature closure, dressed at least daily, and examined frequently.

Because of increasing multi-drug resistance, the CDC now recommends antibiotics with empiric MRSA coverage when local populations display MRSA growth/activity in greater than 10% of cultures.⁴⁷ It is important to aggressively treat MRSA infections, as systemic dissemination of MRSA is associated with increased length of hospital stay, overall treatment cost, and mortality when compared to non-methicillin resistant species.⁴⁸ Antibiotic coverage should be narrowed based on culture sensitivity data. An extended course of intravenous antibiotic therapy is often required for deep space or recurrent infections, as well as osteomyelitis.

Rehabilitation

Soft dressings are preferred post-operatively. When immobilization is necessary, it should be discontinued as early as possible. The use of slings should be avoided as they are unnecessary and cause shoulder and elbow stiffness. Occupational therapy is mandatory and should begin immediately to maximize hand function. Even with appropriate treatment and therapy, residual hand dysfunction is common after infections.

Conclusion

Infection of the upper extremity is a common ailment that nearly all hand surgeons will deal with during their career. These infections come with great variety in their presentation – from simple abscesses to necrotizing fasciitis. Understanding the effect medical comorbidities, drug-use, profession, and geography can have on a patient’s risk of infection, initial presentation, and disease course is mandatory to provide appropriate care. Making a correct diagnosis and providing prompt treatment is required to prevent the long-term sequelae of chronic infection. Many historic principles of treatment remain relevant today.

KEY POINTS.

• Many infections of the hand are the result of direct trauma, leading to large variability in cost of treatment

• Principles developed over a century ago remain relevant in the initial treatment of common hand infections

• Chronic health conditions such as diabetes, HIV, and medical immunosuppression can predispose patients to acute and chronic infections within the upper extremity.

• The majority of upper extremity infections in the US are the result of Community-Acquired MRSA, which presents new and difficult challenges in regard to treating these patients

SYNOPSIS.

Hand infections and their sequalae are relatively common, yet they are serious conditions that can cause considerable morbidity and affect patients’ long term quality of life. Little has changed in regard to basic principles of treating hand infections since first described over a century ago; however, certain chronic health conditions such as diabetes, as well as public health problems like intravenous drug use, have changed the landscape of treating modern hand infections.