INTRODUCTION — The majority of patients with acute hand infections are healthy and active young adults who neglect treatment for minor trauma; more severe infections are seen in patients with impaired immune status.
The initial evaluation and management of hand infection includes a focused history and examination and often involves laboratory evaluation and imaging. The area of erythema should be marked to help document progression of the infection. Empiric antibiotics should be started. Elevation of the hand and arm and application of a heat pack, along with appropriate pain control, will decrease swelling and provide comfort.
Deep hand infections are surgical emergencies. Prompt evaluation and proper treatment of hand infections can mean the difference between an excellent outcome and permanent disability.
The basic principles of evaluating and treating hand infections and considerations for specific hand infections are reviewed here. An overview of the evaluation of hand pain is discussed separately. (See "History and examination of the adult with hand pain".)
GENERAL PRINCIPLES — The general principles of evaluating and treating hand infections are outlined in the next few paragraphs. The specific management of bite wounds, superficial hand infections, and deep space infections are reviewed below. (See 'Bite wounds' below and 'Superficial hand infections' below and 'Deep infections' below.)
History and physical — A focused medical history should determine the possible source of infection, history of progress of the infection, the immune status of the patient, and any relevant past medical history. (See "History and examination of the adult with hand pain", section on 'History'.)
●Symptoms – The onset of hand pain, any loss of hand function, fever and/or chills, and any spontaneous drainage should be documented. Severe throbbing pain is suggestive of an abscess in a confined space. (See 'Deep infections' below.)
A rapid deterioration in general condition is suggestive of severe infections like necrotizing fasciitis. (See 'Necrotizing fasciitis' below.)
●Prior injury – Any prior hand injury from splinters, bites, needle sticks or as a result of attempts at drainage by the patient or other clinicians should be noted.
●Hand dominance – The patient's dominant hand should be documented.
●Occupation – The patient's occupation may increase their exposure to certain infectious agents. An animal handler may be prone to bite wounds that may become infected with organisms typical for the involved species (eg, Pasteurella). A rose gardener is at risk for infection with Sporothrix through the introduction of spores through a cut or puncture wound in the skin. Certain professions are more prone to chronic paronychia. As an example, dishwashers are likely to develop Candida infections, whereas a person employed in a tropical fish aquarium is more likely to develop a Mycobacterium infection after a hand injury. (See 'Bite wounds' below and 'Superficial hand infections' below.)
●Immune status – Host factors that lower immune status increase the risk of significant morbidity from hand infections (eg, diabetes mellitus, chronic kidney disease, malignancy).
Patients should be questioned about any similar lesions elsewhere suggesting hematogenous multifocal presentation or similar episodes in the past and whether they were ever treated for inflammatory arthropathies like rheumatoid arthritis and gout. This medical history combined with clinical examination and investigations can help with the difficult differentiation between an infectious and an inflammatory process. (See 'Differential diagnosis' below.)
On physical examination, vital signs should be taken and recorded and any fever noted. The entire upper extremity should be exposed for a systematic examination. The hand and wrist are examined for the presence of swelling, deformity, open wounds, alignment of the fingers, neurovascular status, and local tenderness. (See "History and examination of the adult with hand pain", section on 'Physical examination'.)
The following findings should be noted:
●Erythema may indicate the presence of cellulitis, lymphangitis, or an underlying abscess. The area of erythema should be outlined with an indelible marker (picture 1). This will allow assessment of progression or regression of the infectious process. We find it extremely valuable in patients in the early stages of necrotizing fasciitis who are not systemically ill. The rapid progression of erythema over one to two hours helps differentiate necrotizing fasciitis from cellulitis and indicates prompt surgical intervention. (See "Necrotizing soft tissue infections" and "Surgical management of necrotizing soft tissue infections".)
●The location of any swelling can provide clues about the anatomic location of a deep infection.
●Fluctuance indicates an underlying abscess (picture 2).
●Discoloration of the skin overlying an abscess indicates ischemia from infective thrombosis of the subdermal and subcutaneous capillaries and potential impending rupture. Central skin necrosis with surrounding erythema (dermonecrosis) is a feature of methicillin-resistant Staphylococcus aureus (MRSA) infections (picture 3).
●Subcutaneous air manifesting as crepitus can be associated with a gas-forming organism (Clostridium, anaerobic streptococcus, and some coliforms), but it is not always infectious in nature (eg, air gun injuries), but this should be apparent from the patient's history.
●Epitrochlear and axillary lymphadenopathy often accompany an infection of the forearm.
●The presence of all four cardinal signs of Kanavel indicate acute infective flexor tenosynovitis [1,2]. These four signs include fusiform swelling of the entire digit, partially flexed posture of the digit, tenderness limited to the course of the flexor tendon sheath, and disproportionate pain on passive extension of the digit.
Laboratory studies — For patients who are systemically ill or immunocompromised, the white blood cell count may help assess the severity of infection and serve as a useful baseline for comparison to monitor the progress treatment. Other studies (eg, renal function, liver function) should be ordered based upon the patient's underlying medical conditions.
Diagnosis and further evaluation — The majority of hand infections can be diagnosed on clinical examination based on the presence of pain, erythema, abnormal swelling, or drainage. (See 'History and physical' above.)
Additional evaluation may point to the specific diagnosis.
Imaging — A radiograph of the affected part should be obtained when indicated by clinical findings and history to evaluate for the following conditions, and as a baseline for future comparison:
●A foreign body can serve as a nidus of infection and may require removal for an infection to resolve (image 1). Radiographs may be misleading if the foreign body is radiolucent.
●The type of radiograph depends on the clinical assessment and suspected injuries, based on the physical examination and mechanism of injury. Consultation with a radiologist is helpful. (See "Overview of finger, hand, and wrist fractures", section on 'Diagnostic imaging'.)
●Periosteal elevation is a nonspecific reaction to tumor, infection, trauma, certain drugs, and some arthritic conditions [3].
●Gas in soft tissue is seen in type I necrotizing fasciitis or gas gangrene caused by clostridia. (See "Clostridial myonecrosis".)
●Radiographs demonstrating periosteal thickening coupled with bone erosion in the setting of a clinical infection may indicate osteomyelitis. However, imaging findings may be subtle or radiographically absent in the first one to two weeks of infection. Imaging of suspected osteomyelitis is discussed in detail elsewhere. (See "Approach to imaging modalities in the setting of suspected nonvertebral osteomyelitis".)
●In the early phase of septic arthritis, the radiographs will show widening of the joint space and surrounding soft tissue swelling. A magnetic resonance imaging (MRI) scan is useful in demonstrating joint effusion and can identify areas of bone involvement or soft tissue abscess. (See "Septic arthritis in adults", section on 'Diagnosis'.)
If a deep abscess is suspected, an ultrasound examination should be performed for confirmation and to look for fluid collections along the tendon sheaths [4]. (See 'Synovial space infections' below.)
Cultures — Blood and wound cultures determine the infective organism and direct specific antimicrobial treatment.
●Blood cultures should be obtained if septic embolism is suspected (eg, patient with recurrent fever, immunocompromised patient, suspected endocarditis).
●For patients with an open or draining wound, a sample of the drainage should be sent for Gram stain and aerobic and anaerobic culture.
Differential diagnosis — A number of inflammatory conditions of the hand may be wrongly diagnosed as an acute infection of the hand. Some of the common conditions that mimic acute hand infections include gout, pseudogout, acute calcific tendinitis, retained foreign bodies, chemotherapeutic infiltration, pyoderma gangrenosum, metastatic tumor, and factitious illness. (See "History and examination of the adult with hand pain".)
●Gout – Gout is a disorder of urate metabolism that leads to high levels of uric acid and the formation of urate crystals. Urate crystals can be deposited under the skin, in joints, and within tendon sheaths as "gouty tophi," which cause an intense inflammatory process. Inflamed gouty tophi may be mistaken for a felon, a subcutaneous abscess, pyogenic flexor tenosynovitis, or septic arthritis (picture 4). (See 'Septic arthritis' below.)
The differentiation between gout and septic arthritis depends on the patient's history, the presence of preexisting gout, and the clinical presentation. If gout is suspected, serum uric acid values and a radiograph should be obtained. It may be difficult to differentiate between gout and infection based only on clinical examination and laboratory and radiological investigations. A trial of colchicine may help differentiate between them. Aspiration of the involved joint and examination of the aspirate under a polarizing light microscope can confirm diagnosis of gout (negatively birefringent needle-shaped intracellular monosodium urate crystals). (See "Clinical manifestations and diagnosis of gout".)
●Pseudogout – Pseudogout (calcium pyrophosphate deposition) is similar to gout except that it is caused by deposition of calcium pyrophosphate crystals rather than urate crystals. As with gout, differentiation from an infection depends on the patient's history, the presence of preexisting underlying diseases, and the clinical presentation. The aspirate in pseudogout shows positively birefringent rhomboid-shaped calcium pyrophosphate crystals under a polarizing microscope. (See "Clinical manifestations and diagnosis of calcium pyrophosphate crystal deposition (CPPD) disease", section on 'Acute CPP crystal arthritis'.)
●Acute calcific tendinitis – Acute calcific tendinitis is caused by deposition of calcium salts around the tendons and ligaments. Patients present acutely with pain, swelling, erythema, and tenderness overlying tendons or ligaments. However, other signs of infection such as fever, lymphadenopathy, or abnormal laboratory values are absent. Radiographs demonstrate characteristic homogenous calcific densities in the area of tenderness (figure 1). This process is self-limiting, and patients are managed conservatively with analgesics, rest, and splintage. (See "Overview of overuse (persistent) tendinopathy".)
●Retained foreign bodies – Retained foreign bodies, especially wooden splinters and thorns, can provoke an inflammatory response that can mimic an infection. Radiographs may be misleading if the foreign body is radiolucent. History is valuable in diagnosis, and removal of the offending foreign body is curative. (See "Infectious complications of puncture wounds".)
●Chemotherapeutic infiltration – The extravasation of chemotherapeutic agents at the site of intravenous access, usually over the dorsum of the hand, may present as marked erythema and swelling. This is frequently seen with use of vesicant chemotherapeutic agents and may be mistaken for a secondary infection. (See "Extravasation injury from chemotherapy and other non-antineoplastic vesicants".)
●Pyoderma gangrenosum – Pyoderma gangrenosum is an inflammatory skin disease commonly misdiagnosed as an infection. (See "Approach to the patient with pustular skin lesions", section on 'Pyoderma gangrenosum'.)
Pyoderma gangrenosum usually begins as small papules that are followed by central necrosis, resulting in a central ulcer with a raised border (picture 5 and picture 6). The diagnosis is often associated with underlying systemic disorders such as inflammatory bowel disease, arthritis, and lymphoproliferative disorders.
●Metastatic tumor – Metastatic tumors to the hand are rare and usually involve the distal phalanx; thus, they can be confused with a pulp space infection or felon (picture 7). Radiographs are useful in differentiating a tumor from infection. Primary lung tumors are the most common metastatic lesion to the hand. Other tumors that metastasize to the hand include breast, kidney, colon, thyroid, and prostate.
Treatment — Most hand infections require urgent surgical evaluation for possible surgical intervention. Necrotizing infections are true surgical emergencies. Prompt evaluation and proper treatment of hand infections can mean the difference between an excellent outcome and permanent disability. Some superficial infections of the hand may respond to nonsurgical management, particularly if it is early in their course. (See 'Deep infections' below and 'Superficial hand infections' below.)
Antibiotic therapy — Antibiotic therapy is an indispensable adjunct to surgical management. The result of culture and sensitivity testing takes two to three days. Therefore, initial antibiotic therapy is empiric based on epidemiologic clues for likely pathogen(s) as well as the Gram stain, if available. Empiric antibiotic therapy should cover skin flora (including Staphylococcus aureus and beta-hemolytic streptococci). First-generation cephalosporins provide appropriate coverage for these organisms. Issues related to coverage for methicillin-resistant S. aureus are discussed separately. (See "Methicillin-resistant Staphylococcus aureus (MRSA) in adults: Treatment of skin and soft tissue infections".)
In addition to the above coverage, empiric anaerobic coverage is also warranted in the setting of bite wounds, as discussed in the following sections. (See "Animal bites (dogs, cats, and other animals): Evaluation and management" and "Human bites: Evaluation and management".)
Tetanus prophylaxis — For hand injuries, tetanus immunization status should be reviewed and booster immunization given accordingly. Tetanus toxoid or tetanus immune globulin may be necessary for patients who have received fewer than three doses of tetanus toxoid or whose immunization status is uncertain. (See "Tetanus-diphtheria toxoid vaccination in adults", section on 'Immunization for patients with injuries'.)
Splinting — Splint immobilization protects the affected area, limits opening of tissue planes restricting the spread of infection, and decreases pain. Splinting in a position of function can help protect against flexion contractures, reduce stiffness, and hasten rehabilitation (picture 8). If a single digit is infected, a splint supporting the interphalangeal joints in extension is usually adequate. (See "Basic techniques for splinting of musculoskeletal injuries" and "Overview of finger, hand, and wrist fractures", section on 'Splinting'.)
Elevation — Elevation helps to reduce edema by improving venous and lymphatic drainage. The goal of elevation is to keep the hand above the level of the heart so that dependent drainage can occur. To accomplish appropriate elevation, patients should be counseled to rest with the extremity above their chest using pillows or commercially available supports while sitting and lying down. The usual arm slings do not provide adequate elevation (picture 9).
Heat — Application of heat increases the delivery of inflammatory cells to the affected area by local vasodilatation, may enhance antibiotic delivery to the tissue, and improves patient comfort. Moist heat is more effective than dry heat. Warm soaks reach maximum vasodilatory effect in approximately 10 minutes. Short, frequent soaks are preferred over continuous immersion. For more severe infections for which soaks are inadvisable, the affected part can be wrapped in moist hot towels and then covered with plastic wrap to create a vapor barrier, with a dry towel to insulate [5,6].
BITE WOUNDS
Animal bites — Dogs are responsible for the majority of animal bites, but cat bites are responsible for the majority of bites that result in infection (76 percent). Dog bites result in larger wounds from the crushing effect of blunt teeth and strong jaws, whereas cat bites result in multiple small puncture wounds (picture 10) that appear innocuous at presentation. However, the cat's sharp teeth can deeply penetrate soft tissues and inoculate bacteria into closed spaces, such as tendon sheaths and joints. The organism commonly found in animal bite wounds is Pasteurella multocida, which is a gram-negative, nonspore-forming coccobacillus that is found in the normal oral flora of many animals, including dogs and cats. Animal bite wounds can be treated by outpatient observation and oral antibiotics (typically amoxicillin-clavulanate) or by inpatient admission for intravenous antibiotics, and if indicated, surgical irrigation and debridement. However, it is difficult to predict who will fail outpatient treatment and need hospitalization. Clinical findings that suggest a more severe, deeper-seated infection include location of the bite over a joint or tendon sheath, erythema, pain, and swelling. These findings should warrant hospitalization and urgent consultation with a hand surgeon (picture 10) [7]. The management of animal bites is discussed in detail elsewhere. (See "Animal bites (dogs, cats, and other animals): Evaluation and management".)
The rabies immunization status of the animal should be documented (if known), and cat owners should be asked whether their cats hunt and eat wild animals. Such cats are at risk of carrying Francisella tularensis, which can cause tularemia. (See "Indications for post-exposure and pre-exposure rabies prophylaxis" and "Tularemia: Clinical manifestations, diagnosis, treatment, and prevention".)
Human bites — Human bites are serious injuries because of the virulence of the human oral flora [8,9].
The most common human bite injury to the hand is clenched fist injury, also known as a "fight bite." These injuries can be missed in the emergency department because patients may be reluctant to provide an accurate account of the injury and the initial wound may appear innocuous.
Fight bite injuries to the hand usually occur with the fist in a clenched position. When the fist makes contact with a victim's mouth, the teeth can easily penetrate the skin and extensor tendon that are stretched tightly over the metacarpal head, thus injuring the underlying bone, cartilage, or joint and resulting in an open metacarpal head fracture, which may progress to septic arthritis (figure 2).
Patients with fight bites present with a lack of normal active extension of the involved joint (extension lag), pain, swelling, and erythema. Purulent drainage from the wound may also be seen.
When a patient with a fight bite injury is examined with their digits extended, the small skin laceration may no longer correspond to the site of any fracture, which is frequently overlooked (picture 11). Thus, a radiograph (Brewerton view) should be obtained to look for a fracture of the metacarpal head, retained foreign body (tooth fragment), or osteomyelitis in a delayed presentation. (See "Metacarpal head fractures".)
Human bite injuries often require hospital admission, antibiotics, debridement in the operating room, and delayed wound closure. Wide exposure of the wound is required, and the joint should be opened and inspected, even if the joint capsule appears intact (picture 12). After cleansing and debridement, the wound can be left open or loosely approximated.
The tendon can be repaired at the time of washout if the surgeon feels an adequate debridement was achieved, but if this is not the case, the tendon repair and skin closure can be delayed until the infection has been eradicated. If the clinical symptoms do not improve, radiographs should be repeated and compared with initial radiographs to rule out osteomyelitis. The management of infections from human bites is discussed in detail elsewhere. (See "Human bites: Evaluation and management".)
SUPERFICIAL HAND INFECTIONS — Superficial hand infections arise from the skin and subcutaneous tissue in a plane superficial to the tendons [10,11]. These include cellulitis, lymphangitis, paronychia, pulp space infections, herpetic whitlow, subcutaneous abscess, and web space abscess. As a superficial hand infection progresses, it follows the path of least resistance and may involve deeper tissue planes. (See 'Deep infections' below.)
Cellulitis — Cellulitis is a diffuse infection of the subcutaneous tissue without pus formation and is characterized by a warm, tender area of erythema and edema that is well demarcated and progresses over time (picture 13). The movements of any underlying joints are painful and restricted.
The patient with cellulitis of the hand requires hospital admission for rest, elevation, warm soaks, antibiotics, and close monitoring. If there is no response to antibiotic therapy (indicated by improvement in patient symptoms and regression of area of erythema), pus formation or a more serious deep hand infection is likely. The diagnosis and treatment of cellulitis is discussed in detail elsewhere. (See "Cellulitis and skin abscess: Epidemiology, microbiology, clinical manifestations, and diagnosis" and "Acute cellulitis and erysipelas in adults: Treatment" and "Soft tissue infections following water exposure".)
Lymphangitis — Lymphangitis of the hand or arm is an infection of the lymphatics. Like cellulitis, it is non-pus-forming. However, unlike cellulitis, it has a distal nidus with erythematous streaks that spread proximally up the arm (picture 14). There may be associated palpable tender epitrochlear or axillary lymphadenopathy.
A patient with lymphangitis requires hospital admission for rest, elevation, warm soaks, antibiotics, and close monitoring. If there is no response to antibiotic therapy, a more serious deep hand infection is likely. The diagnosis and treatment of lymphangitis is discussed in detail elsewhere. (See "Lymphangitis" and "Soft tissue infections following water exposure".)
Paronychia — Acute paronychia is a bacterial infection of the lateral nail fold characterized by erythema, swelling, and tenderness along the nail fold, especially in the dorsolateral corner (picture 15) [12,13]. Chronic paronychia is an inflammatory dermatosis of the nail fold due to chronic exposure to irritants and allergens (picture 16). The diagnosis and treatment of acute and chronic paronychia is discussed elsewhere. (See "Paronychia".)
If left untreated, acute paronychia can form an abscess within the nail fold. It usually begins in the lateral nail fold (paronychium), gradually progressing to involve the proximal nail fold (eponychium) and then the opposite lateral nail fold (runaround abscess). The nail plate may be lifted up, and, in some cases, the infection can extend to the pulp space (picture 17)
Nonsurgical treatment of acute paronychia and acute eponychia is appropriate in patients who present early without an abscess and consists of oral antibiotics, warm soaks, rest, and elevation.
Surgical drainage is indicated in patients who present with an abscess (figure 3 and figure 4).
Pulp space infections — The digital pulp, the fleshy mass at the digital tips, is divided into multiple compartments by fibrous septae that provide structural support (figure 5) [10,11]. A severe infection or abscess of the pulp space, called a felon, results in increased pressure and can lead to ischemic necrosis of surrounding tissue, osteomyelitis, flexor tenosynovitis, or septic arthritis of the distal interphalangeal joint (DIPJ).
Pulp abscesses account for 15 to 20 percent of all hand infections. The thumb and index finger are the most commonly affected digits [14]. A pulp abscess usually occurs after a puncture wound but may also result from untreated acute paronychia. (See 'Paronychia' above.)
Patients with pulp space infections present with pain, cellulitis, and an associated tender fluctuant swelling. The pain is severe and throbbing, is worse in the dependent position, and usually does not allow the patient to sleep. The swelling is limited to the soft tissue around the distal phalanx, and an area of imminent rupture (pointing) may be obvious (figure 5). Occasionally, the abscess may spontaneously discharge through the skin, decompressing it and thus reducing symptoms. A radiograph should be obtained to look for any retained foreign bodies and rule out involvement of the distal phalanx.
A very early presentation of a pulp space infection without a fluctuant swelling may be treated with warm soaks, rest, elevation, and oral antibiotics. However, most patients with a pulp abscess require surgical intervention. A simple incision and drainage procedure may provide temporary relief; however, in our experience, debridement of the abscess cavity is best accomplished in the operating room because the infection may be more extensive than the symptoms and clinical appearance suggest (figure 6).
Herpetic whitlow — Herpetic whitlow is a viral infection of the hand caused by herpes simplex virus (HSV-1 and HSV-2). Herpetic whitlow has a bimodal age distribution affecting children less than 10 years of age and young adults between 20 and 30 years of age.
HSV has been isolated from the saliva of about 2.5 percent of normal adults [15,16]. HSV spreads by direct digital contact with secretions, from lesions of infected patients, or from secretions of asymptomatic carriers. Herpetic whitlow is caused by HSV-1 in children, and in adults, it can be caused by either HSV-1 or HSV-2. HSV-1 is also responsible for gingivostomatitis in children and adults. HSV-2 is responsible for genital herpes in sexually active adults. (See "Epidemiology, clinical manifestations, and diagnosis of herpes simplex virus type 1 infection" and "Herpetic gingivostomatitis in young children" and "Epidemiology, clinical manifestations, and diagnosis of genital herpes simplex virus infection".)
The lesion in herpetic whitlow is a single vesicle or a cluster of vesicles, The lesions are initially clear but become turbid, yellow, and appear purulent with an erythematous base (picture 18 and picture 19 and picture 20). These lesions appear after an incubation period of 2 to 20 days following inoculation and can coalesce to form larger blisters. The lesions may spread around the paronychial folds, and satellite lesions may appear. When the blister (or vesicle) is unroofed, non-purulent fluid is released, and the underlying tissue has a honeycomb appearance that is diagnostic for herpetic whitlow. The lesions are associated with tingling and burning pain of the hand that is disproportionate to the clinical findings. Occasionally patients have flu-like symptoms, including fever and epitrochlear/axillary lymphadenitis. Herpetic whitlow is often confused with acute paronychia or a pulp abscess (see 'Pulp space infections' above). However, unlike a bacterial infection, the pulp space is not tense. Herpetic whitlow usually affects only one digit; if multiple digits are affected, other vesicle-forming viral infections like the Coxsackievirus infection (enterovirus) should be suspected. (See "Hand, foot, and mouth disease and herpangina".)
The vesicles evolve into shallow ulcers that form crusts that eventually peel off to leave healed epidermis below. The satellite lesions, shallow ulcers, and crusts last for about 12 days and coincide with the period of viral shedding, during which time the patients are most infectious. Complications from herpetic whitlow are rare and include nail dystrophy, hyperesthesia, and systemic viremia. The natural history of untreated uncomplicated herpetic whitlow is complete resolution within three weeks. After an infection, HSV passes into a latent phase residing in the sensory ganglion. About 20 to 50 percent of affected patients experience recurrence that may be triggered by illness, fever, sun exposure, menstruation, or other physiological or psychological stressors. Recurrent infections are typically milder and shorter in duration [15].
The diagnosis of herpetic whitlow is clinical. Diagnostic tests include viral culture, serum antibody titers, Tzanck smear, and lesion-specific antigen detection [15]. Viral culture is most sensitive but requires one to four days for a positive result. Serum antibody titers take about three weeks. Thus, both these tests are not useful for rapid confirmation. A Tzanck smear or antigen detection in samples of vesicle fluid or scrapings can be used for early diagnosis. However, the Tzanck smear is not specific for HSV, but it is relatively inexpensive. (See "Office-based dermatologic diagnostic procedures", section on 'Tzanck smear'.)
The treatment of primary herpetic whitlow is conservative (rest, elevation, and anti-inflammatory agents). Unless a secondary bacterial infection is suspected, herpetic whitlow does not require use of antibiotics. A dry dressing is used to cover the digit to prevent transmission of the infection. Surgery is contraindicated because it will only spread the infection and may result in secondary bacterial infection. Topical 5% acyclovir shortens the duration of labial and genital HSV lesions but has not been studied in herpetic whitlow. The use of oral acyclovir has been suggested in immunocompetent patients with recurrent disease or primary disease at multiple sites; a total daily dose of 1600 to 2000 mg given at the onset of prodromal symptoms has been shown to prevent viral shedding and shorten the duration of symptoms. Similarly, 200 mg of acyclovir taken orally three to four times daily has been shown to prevent or decrease recurrence rates. However, the dose and duration of treatment have not been optimized [15]. Intravenous acyclovir is recommended only for immunocompromised patients or those with disseminated HSV infections. In summary, immunocompetent patients with primary herpetic whitlow may benefit from topical acyclovir therapy, whereas patients with primary HSV infection at multiple sites or recurrent herpetic whitlow may be considered for oral antiviral therapy [16].
Subcutaneous abscess — A subcutaneous abscess of the digits or hand is usually the result of minor penetrating trauma that was neglected.
A subcutaneous abscess of the digit presents with localized swelling, erythema, and restricted motion at the adjacent joints (picture 21). The digit is usually in a flexed posture, and there may be evidence of an inflamed puncture wound from a penetrating injury. In late presentations, the abscess may be pointing or discharging through a sinus.
Subcutaneous abscesses of the hand can occur on the palmar or the dorsal aspect of the hand.
●Abscesses of the palmar skin are typically localized because the fibrous septae anchoring palmar skin limit the spread of infection (picture 22). A subcutaneous abscess of the palm presents with erythema and mild swelling on both the palmar and dorsal aspect of the hand. Palpation of the tendon sheath proximal and distal to a palmar subcutaneous abscess will help differentiate it from pyogenic flexor tenosynovitis that is confined along the path of the tendon sheath.
●By contrast, the dorsal skin of the hand is loosely anchored to the underlying tissue, which allows the spread of infection into two potential spaces: the dorsal subcutaneous space, which is superficial to the extensor tendons, and the dorsal subaponeurotic space, which is deep to the extensor tendons (figure 7). A subcutaneous abscess of the dorsum of the hand is associated with significant dorsal hand swelling, a tender fluctuant mass, and pain with extension of the digits.
A radiograph should be obtained to look for any foreign bodies and rule out involvement of the bone or joints.
Drainage to decompress the abscess will reduce pain in the period before surgical debridement can be performed. Patients who require extensive debridement for dorsal abscesses may need additional surgical procedures to cover the resulting soft tissue defect (picture 23).
Web space abscess — An interdigital web space infection is a subcutaneous abscess involving the web space where the infection may be present on the palmar and dorsal aspect simultaneously (picture 24 and figure 8). It is also known as a collar button abscess because of its anatomic resemblance to buttons used on dress shirts in the early nineteenth century. Advanced web space abscesses of the collar button types are rarely seen in modern times unless the infection is neglected.
A web space abscess usually results from a penetrating injury or a fissure in the web space. It may also result from infection of a palmar callus in manual laborers or spread from an adjacent palmar subcutaneous abscess. The infection begins in the palmar subcutaneous portion of the web space and then spreads dorsally over the superficial transverse metacarpal ligament to involve the dorsal subcutaneous space.
A patient with a web space abscess presents with pain and swelling limited to the web space and distal palm. There may be greater swelling on the dorsal aspect of the web, although the primary focus of infection is on the palmar side. The adjacent digits are usually in an abducted position, and this may help differentiate it from a pure dorsal or palmar subcutaneous abscess, where the digits are in the normal adducted position.
A web space abscess requires a combined palmar and dorsal surgical approach for adequate drainage and debridement (figure 9).
DEEP INFECTIONS — Deep hand infections involve the tendons and structures deep to the tendon sheaths. These include synovial space infections, deep fascial space infections, septic arthritis, and necrotizing fasciitis. In the early stage, the infection is limited by the compartmentalized anatomy of the hand, and, if left untreated, they may rupture superficially, spread to the adjoining compartments, or go deeper to involve the underlying bone and joints [10,11].
Although uncommon, both typical and atypical mycobacterial infections should be considered in the differential diagnosis of hand infections that are refractory to treatment. Mycobacterial infections are typically associated with the tendon sheath and synovial tissues lining the tendon. A tissue biopsy should be obtained if the diagnosis is suspected because mycobacteria are difficult to culture. (See "Cutaneous manifestations of tuberculosis" and "Soft tissue infections following water exposure".)
Synovial space infections — The flexor tendons of the hand are enclosed in a double-layered synovial sheath composed of an inner visceral layer and an outer parietal layer, which create a closed system (figure 10). The tendon sheath of the flexor pollicis longus continues proximally as radial bursa while the tendon sheaths of the fingers (usually the ulnar digits) continue proximally as the ulnar bursa. The radial and ulnar bursa end proximal to the wrist. They can communicate with each other via the space of Parona, which is a potential space deep to the tendons of the flexor digitorum profundus (sublimis) and superficial to the pronator quadratus.
The synovial spaces intercommunicate and provide an optimal environment for bacterial growth because they are poorly vascularized and rich in synovial fluid [2,10,17]. Bacterial proliferation within the synovial sheath rapidly destroys the tendon's gliding mechanism and leads to increased pressure within the sheath, which obstructs the blood flow and can cause tendon necrosis and rupture. The infection can spread from the bursa into the surrounding soft tissue compartments. The infection can also track from the radial to the ulnar bursa and vice versa to form a so-called horseshoe abscess.
Patients with an isolated infection of the digital flexor sheaths (pyogenic flexor tenosynovitis) typically present with fusiform swelling of the whole digit, partially flexed posture of the digit, tenderness along the flexor tendon sheath, and pain on passive extension of the digit (Kanavel's cardinal features of pyogenic flexor tenosynovitis), although all features may not be seen in an early presentation (picture 25) [1,2].
Patients with an infection of the radial bursa, ulnar bursa, space of Parona, or a combination of these (horseshoe abscess) present with a flexed attitude of the wrist; swelling; and tenderness along the thenar, hypothenar, and/or the distal wrist crease because of the associated thumb and/or small finger flexor tenosynovitis.
In general, the management of tenosynovitis requires surgical intervention and antibiotic therapy (picture 26). Synovial space infections are discussed in detail elsewhere. (See "Infectious tenosynovitis".)
Deep fascial space infections — Deep fascial space infections are surgical emergencies; there is no role for nonoperative treatment.
The palm has three potential closed spaces with well-defined anatomic borders: the thenar, the midpalmar, and the hypothenar space (figure 11) [18]. These spaces are deep to the flexor tendons but superficial to the interosseous muscles. Infections in these spaces most commonly occur following a penetrating injury but occasionally can result from extension from a subcutaneous abscess, adjacent pyogenic flexor tenosynovitis, or hematogenous spread from a distant site.
All deep palmar space infections present with palmar swelling and tenderness over the involved palmar space and generalized dorsal swelling:
●A thenar space abscess is characterized by a widely abducted thumb and fullness on the dorsum of the first web space, with pain on adduction or opposition of the thumb (picture 27).
●A midpalmar space abscess is characterized by loss of the normal palmar concavity (picture 28). The long and ring fingers assume a partially flexed posture, and there is pain on passive extension of these fingers.
●Hypothenar space infections have much less palmar and dorsal swelling than thenar or midpalmar space infections. In addition, there is no involvement of the fingers or the flexor tendons.
An ultrasound examination can help in confirming the presence and location of an abscess cavity and thus differentiate deep fascial space infection from other entities in the differential diagnosis such as pyogenic flexor tenosynovitis, radial or ulnar bursal infections, and subcutaneous abscess. Radiographs are useful to evaluate for a retained foreign body.
The incisions used to approach to thenar space, midpalmar space, and hypothenar space infections are illustrated in the figures (figure 12 and figure 13 and figure 14).
Septic arthritis — Septic arthritis usually refers to bacterial infection in a joint but also includes fungal and mycobacterial infections that involve the joint [19].
Patients with septic arthritis present with a red, swollen, warm, and tender joint that is painful on passive motion. The differential diagnosis of bacterial arthritis includes gout, pseudogout, arthritis, and Lyme disease, each of which can present with acute involvement of one or a few joints (table 1).
Treatment of acute bacterial arthritis requires appropriate antimicrobials and adequate joint drainage. All septic joints must be explored early to avoid cartilage damage from the disease process (picture 29). The diagnosis and treatment of septic arthritis is discussed in detail elsewhere. (See "Septic arthritis in adults".)
Necrotizing fasciitis — Necrotizing fasciitis is a rapidly progressing, life-threatening soft tissue infection characterized by widespread fascial necrosis and relative sparing of underlying muscle caused by a toxin-producing bacterium [20,21]. (See "Necrotizing soft tissue infections", section on 'Necrotizing fasciitis'.)
Patients with necrotizing fasciitis feel much worse than suggested by their clinical appearance and may demonstrate systemic signs of sepsis including fever, dehydration, hypotension, and electrolyte imbalance. It is important to differentiate necrotizing fasciitis from cellulitis because the early presentation of both these conditions is similar. (See 'Cellulitis' above.)
Necrotizing fasciitis requires urgent surgical intervention. Initial treatment involves resuscitation and stabilization of the patient and empiric broad-spectrum antimicrobial therapy. Thereafter, the initial debridement should be performed as soon as possible. Other adjunctive therapies are discussed elsewhere. (See "Surgical management of necrotizing soft tissue infections", section on 'Optimal facility for initial debridement'.)
Surgical treatment consists of wide debridement of skin, subcutaneous tissue, fascia, and any necrotic muscle. The initial debridement is the most important and determines the outcome of treatment (picture 30). The diagnosis and treatment of necrotizing fasciitis is discussed in detail elsewhere. (See "Surgical management of necrotizing soft tissue infections", section on 'Surgery'.)
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Human bites" and "Society guideline links: Rabies" and "Society guideline links: Skin and soft tissue infections".)
SUMMARY AND RECOMMENDATIONS
●Evaluation – Prompt evaluation and proper treatment of hand infections can mean the difference between an excellent outcome and permanent disability. Initial evaluation includes a focused history and examination, laboratory evaluation, and imaging. The area of erythema should be marked to help document progression of the infection. With bite wounds, rabies immunization status should be documented. (See 'General principles' above and 'Bite wounds' above.)
•Superficial infections – Superficial hand infections arise from the skin and subcutaneous tissue in a plane superficial to the tendons. These include cellulitis, lymphangitis, paronychia, pulp space infections, herpetic whitlow, subcutaneous abscess, and web space abscess. As a superficial hand infection progresses, it follows the path of least resistance and may involve deeper tissue planes. (See 'Superficial hand infections' above.)
•Deep infections – Deep hand infections are deep to the tendon sheaths and include synovial space infections, deep fascial space infections, septic arthritis, and necrotizing fasciitis. Although less common overall, both typical and atypical mycobacterial infections should be suspected with hand infections that are refractory to treatment (typically deep infection). Because mycobacteria are difficult to culture, a tissue biopsy is often necessary. (See 'Deep infections' above.)
●Differential diagnosis – Acute hand infections may be mistaken for several inflammatory or other conditions of the hand. Some of these include gout, pseudogout, acute calcific tendinitis, retained foreign bodies, chemotherapeutic infiltration, pyoderma gangrenosum, and metastatic tumor. (See 'Differential diagnosis' above.)
●Management – Early and superficial infections of the hand may respond to nonsurgical management. Empiric antibiotics should be initiated, and hand elevation and heat will provide comfort for the patient. Most acute infections of the hand require early surgical intervention. (See 'Treatment' above.)
