Hand infections

Question 1

What is a hand infection, and what is its most common cause?

Answer 1

A hand infection is a bacterial, viral, or fungal invasion of hand tissues, most commonly caused by trauma (e.g., penetrating injuries or bites).

Question 2

What distinguishes a superficial hand infection from a deep one?

Answer 2

Superficial infections affect skin/subcutaneous tissue and are treated with antibiotics/splinting; deep infections involve tendon, joint, or bone, requiring surgical irrigation and debridement.

Question 3

What does ‘polymicrobial’ mean in the context of hand infections?

Answer 3

Involving multiple pathogens (e.g., Staphylococcus and Streptococcus), seen in over 50% of hand infections, often from trauma or bites.

Question 4

Which hand tissue is most commonly infected, and why might this be?

Answer 4

Dorsal subcutaneous tissue; it’s exposed to trauma and less protected than deeper structures.

Question 5

What does ‘DICE’ stand for in treating hand infections?

Answer 5

Drainage/debridement, Immobilization, Chemotherapy (antibiotics), Elevation.

Question 6

What patient factors increase the risk of hand infections?

Answer 6

Immunocompromised states, IV drug use, diabetes, steroid use, microvascular disease, or prior trauma.

Question 7

What type of pathogen is Staphylococcus aureus, and why is it significant in hand infections?

Answer 7

It’s a Gram-positive bacterium, the most common cause (50-80%) of hand infections due to its prevalence on skin and ability to form abscesses.

Question 8

What type of pathogen is beta-hemolytic Streptococcus, and where is it commonly found?

Answer 8

A Gram-positive bacterium, frequent in hand infections (often with Staphylococcus aureus) causing cellulitis or polymicrobial infections.

Question 9

Which bacterium is most commonly linked to paronychia, and where does it occur?

Answer 9

Staphylococcus aureus; it infects the eponychial fold (skin around the nail).

Question 10

What pathogen dominates human bite infections at the MCP joint, and why is this site notable?

Answer 10

Alpha-hemolytic Streptococcus; the MCP joint (‘fight bites’) is vulnerable due to clenched-fist injuries penetrating deep tissue.

Question 11

What unique bacterium appears in one-third of human bite wounds, and why is it dangerous?

Answer 11

Eikenella corrodens; it rapidly destroys cartilage and requires 10% CO2 for culture.

Question 12

Which pathogen is typical in animal bites, and what’s its key trait?

Answer 12

Pasteurella multocida; a Gram-negative bacillus common in cat/dog bites.

Question 13

What viral infection is most common in HIV patients’ hands, and what’s its key feature?

Answer 13

Herpes simplex; causes herpetic whitlow with painful vesicles and prolonged shedding.

Question 14

Which fungal organism causes chronic paronychial infections, and who’s at risk?

Answer 14

Candida albicans; affects those with constant moisture exposure (e.g., dishwashers).

Question 15

What bacterium is the top cause of pyogenic flexor tenosynovitis, and what structure does it infect?

Answer 15

Staphylococcus aureus; the flexor tendon sheath.

Question 16

What pathogen is uniquely common in diabetic hand infections, and what’s a distinctive feature?

Answer 16

Gram-negative bacteria; subepidermal abscesses are typical.

Question 17

Which bacterium is most common in felons, and why is it prevalent?

Answer 17

MRSA (methicillin-resistant Staphylococcus aureus); it thrives in closed-space infections like the digital pulp.

Question 18

What pathogen causes hand infections in renal transplant diabetic patients, and why is morbidity high?

Answer 18

Often deep polymicrobial infections; immunosuppression and diabetes impair healing.

Question 19

Which bacterium causes cellulitis of the hand most often, and what’s its group?

Answer 19

Group A beta-hemolytic Streptococcus; a Gram-positive pathogen.

Question 20

What organism is linked to coastal/brackish water hand infections, and what’s its treatment?

Answer 20

Vibrio vulnificus; treated with tetracycline or chloramphenicol.

Question 21

What bacterium is associated with freshwater hand infections, and what’s its treatment?

Answer 21

Mycobacterium marinum; rifampin, ethambutol, or TMP-SMX.

Question 22

What fungal pathogen causes sporotrichosis in the hand, and how does it enter?

Answer 22

Sporothrix schenckii; via thorn pricks or soil contact, common in gardeners.

Question 23

What algal pathogen is most common in fishermen’s hand infections?

Answer 23

Prototheca wickerhamii; treated with tetracycline.

Question 24

What viral pathogen causes milker’s node or granuloma in the hand?

Answer 24

Pox virus; from contact with infected cows.

Question 25

What type of flexor tenosynovitis results from hematogenous spread, and its pathogen?

Answer 25

Gonococcal infection; Neisseria gonorrhoeae.

Question 26

What are the hallmark signs of hand cellulitis, and what might indicate severity?

Answer 26

Erythema, swelling, tenderness; lymphangitis suggests worsening spread.

Question 27

What defines a felon, and what’s its most common site?

Answer 27

A closed-space infection of the digital pulp; fingertip pulp.

Question 28

What is a runaround abscess, and how does it differ from typical paronychia?

Answer 28

A paronychial abscess tracking beneath the entire nail fold; it’s more extensive than localized paronychia.

Question 29

What’s the natural progression of herpetic whitlow if untreated?

Answer 29

Self-limiting over 3-4 weeks: pain/tingling (48-72 hours), then vesicles turn to ulcers (10-14 days); 20% recur.

Question 30

Which fingertip area is most resistant to infection, and why?

Answer 30

Hyponychium; its tough, keratinized skin acts as a barrier.

Question 31

What are the four cardinal signs of pyogenic flexor tenosynovitis?

Answer 31

1. Flexed resting position, 2. Tenderness over flexor sheath, 3. Pain on passive extension, 4. Fusiform swelling.

Question 32

Which lab values support a flexor tenosynovitis diagnosis, and why are they specific?

Answer 32

Elevated WBC, ESR, or CRP; at least one with a positive exam is 100% specific for infection.

Question 33

What is a horseshoe abscess, and how does it form?

Answer 33

Infection of thumb or small finger flexor sheath spreading via radial and ulnar bursae; a contiguous spread.

Question 34

What indicates proximal spread of small finger tenosynovitis into Parona’s space?

Answer 34

Sudden onset of acute carpal tunnel syndrome.

Question 35

What is Parona’s space, and what are its key borders?

Answer 35

A potential space at the wrist; borders: pronator quadratus, pollicis longus, flexor carpi ulnaris.

Question 36

What is a collar button abscess, and how is it distinguished from a dorsal subcutaneous abscess?

Answer 36

Infection of the interdigital subfascial webspace; abducted resting posture of adjacent digits.

Question 37

What is a dumbbell or pantaloon abscess, and where does it occur?

Answer 37

Infection spanning thenar space, first webspace, and dorsoradial hand.

Question 38

Why is the thumb markedly abducted in thenar space infections?

Answer 38

Reduces pressure and pain on the inflamed adductor pollicis.

Question 39

What infection causes loss of palmar concavity, and why?

Answer 39

Midpalmar space infection; swelling fills the natural hollow.

Question 40

What is an interdigital pilonidal cyst, and how does it become infected?

Answer 40

A foreign hair in the webspace; secondary bacterial infection follows penetration.

Question 41

Which flexor tendon zone is most commonly infected, and why?

Answer 41

Zone II; dense tendon sheath anatomy traps infection.

Question 42

What cultures are requested for diagnosing hand infections?

Answer 42

Aerobic, anaerobic, and Lowenstein-Jensen medium for atypical mycobacteria.

Question 43

Which stains are used to identify hand infection pathogens?

Answer 43

Gram stain, Ziehl-Neelsen (mycobacteria), and Tzanck smear (herpes).

Question 44

What preparation is needed to diagnose a suspected fungal hand infection?

Answer 44

Potassium hydroxide (KOH) to dissolve tissue and reveal fungi.

Question 45

How is acute paronychia without abscess managed, and why?

Answer 45

Warm water soaks and oral antibiotics; promotes drainage and fights infection non-surgically.

Question 46

What’s the treatment for paronychia with abscess, and what’s a common step?

Answer 46

Incision and drainage; often includes nail plate removal to access the abscess.

Question 47

How is chronic paronychial infection by Candida albicans treated?

Answer 47

Marsupialization, nail removal, and topical corticosteroid-antifungal ointment (e.g., 3% clioquinol in triamcinolone-nystatin).

Question 48

How are human bite injuries treated surgically, and why is the wound left open?

Answer 48

Surgical extension, debridement, arthrotomy; left open to prevent closure over residual bacteria.

Question 49

What’s the preferred incision for draining a felon, and why avoid the fishmouth incision?

Answer 49

Mid-volar or high lateral incision; fishmouth risks vascular compromise to the pulp.

Question 50

What are the consequences of an undrained felon?

Answer 50

Deep-space infections, septic arthritis, osteomyelitis, amputation, or painful/insensate pulp scars.

Question 51

How are superficial hand infections typically treated?

Answer 51

Antibiotics (14-21 days) and splinting, depending on severity.

Question 52

How are deep hand infections managed?

Answer 52

Surgical irrigation and debridement, antibiotics, and splinting.

Question 53

What’s the treatment for herpetic whitlow in immunocompromised patients, and why?

Answer 53

Antivirals; it won’t resolve spontaneously due to weakened immunity.

Question 54

Does irrigation and debridement help herpetic whitlow, and why not?

Answer 54

No; it may cause bacterial superinfection by disrupting healing tissue.

Question 55

How long does viral shedding persist in herpetic whitlow?

Answer 55

Until lesion epithelialization is complete.

Question 56

What’s the drug of choice for MSSA hand infections?

Answer 56

Cephalexin or Augmentin (amoxicillin-clavulanate).

Question 57

What antibiotics are used for MRSA hand infections, and when is IV vs. oral chosen?

Answer 57

IV: Vancomycin; Oral: Bactrim, clindamycin, or ciprofloxacin; IV for severe cases, oral for milder ones.

Question 58

What’s the current reported incidence of MRSA in hand infections?

Answer 58

34-73%, and rising due to antibiotic resistance.

Question 59

What are potential side effects of aminoglycosides (e.g., gentamicin) in hand infection treatment?

Answer 59

Nephrotoxicity (kidney damage) and ototoxicity (hearing loss).

Question 60

What’s required to diagnose and treat an animal bite infection?

Answer 60

X-ray (for bone/foreign bodies), antibiotics (Augmentin or IV Unasyn), and irrigation.

Question 61

How are early (<24 hours) suppurative flexor tenosynovitis infections treated?

Answer 61

Elevation, splinting, and IV antibiotics; surgery avoided if caught early.

Question 62

What’s the management for late (>24 hours) flexor tenosynovitis infections?

Answer 62

Surgical irrigation of the tendon sheath plus IV antibiotics.

Question 63

What’s the empiric antibiotic regimen for pyogenic flexor tenosynovitis, and how long?

Answer 63

Vancomycin + piperacillin-tazobactam (Zosyn) for 2-3 weeks.

Question 64

Why is catheter placement critical in limited incision irrigation for tenosynovitis?

Answer 64

Fluid outside the digital sheath can cause compartment syndrome.

Question 65

What’s the favored exposure for severe tenosynovitis with purulence or necrosis?

Answer 65

Open sheath exposure via midaxial approach, sparing A2 and A4 pulleys.

Question 66

Which two digital flexor sheaths communicate with palm bursae, risking proximal spread?

Answer 66

Thumb (radial bursa) and small finger (ulnar bursa); extend to carpal tunnel in 50-80% of people.

Question 67

Can index finger sheath infection spread to the thenar space?

Answer 67

Yes; due to anatomical proximity.

Question 68

What are the deep hand spaces that can become infected?

Answer 68

Dorsal subaponeurotic, thenar, midpalmar, Parona’s, and interdigital subfascial web spaces.

Question 69

What infection site corresponds to the midpalmar space?

Answer 69

Ring or middle finger flexor tendon sheath.

Question 70

What infection site corresponds to the thenar space?

Answer 70

Index finger flexor tendon sheath.

Question 71

What infection site corresponds to the dorsal subaponeurotic space?

Answer 71

Deep to the extensor tendon aponeurosis.

Question 72

What infection site corresponds to the dorsal subcutaneous space?

Answer 72

Entire dorsum of the hand.

Question 73

What are the most common pathogens in deep space hand infections?

Answer 73

Streptococcus, Staphylococcus aureus, and coliform organisms.

Question 74

How is a collar button abscess treated?

Answer 74

Incision and drainage with broad-spectrum antibiotics.

Question 75

What are the boundaries of the thenar space?

Answer 75

Volar: index finger flexor tendon; Dorsal: adductor pollicis; Radial: adductor pollicis insertion and thenar fascia; Ulnar: midpalmar septum.

Question 76

What incisions are recommended for thenar space infection drainage?

Answer 76

Combined volar (thenar eminence) and dorsal (first webspace axial to second MC) incisions.

Question 77

Why are incisions parallel to the first-web commissure avoided in thenar space infections?

Answer 77

To prevent webspace contracture.

Question 78

What are the boundaries of the midpalmar space?

Answer 78

Volar: flexor tendons and lumbricals; Dorsal: middle and ring finger metacarpals; Radial: midpalmar septum; Ulnar: hypothenar muscles.

Question 79

What’s the treatment of choice for sporotrichosis in the hand?

Answer 79

Oral potassium iodide; itraconazole if iodine-allergic.

Question 80

What’s the infection rate after elective hand surgery?

Answer 80

1-7%; 0.47% for deep infections after carpal tunnel release.

Question 81

What conditions can mimic hand infections?

Answer 81

Gout, pseudogout, pyogenic granuloma, pyoderma gangrenosum, and neoplasia.