Courtesy:
Stewart Elkowitz MD
Assistant Clinical Professor,
NYU Langone Orthopaedics
Hand Infections — High-Yield Review
1. Common Organisms
The most common organisms in hand infections are:
- Staphylococcus aureus
- Beta-hemolytic Streptococcus
Staphylococcus aureus accounts for a large proportion of hand infections.
Other organisms to consider include:
- Gram-negative bacteria
- Mycobacteria
- Fungal organisms
Certain exposures suggest particular organisms:
- Human bites: Eikenella
- Animal bites: Pasteurella
- Farm injuries and animal bites are frequently polymicrobial.
Important
MRSA is increasingly prevalent, particularly in hand infections.
2. Cellulitis
Cellulitis is an infection of the:
- Skin
- Subcutaneous tissue
There is no abscess or fluid collection.
Treatment
If diagnosed early:
- Oral antibiotics
- Splinting
- Elevation
Splinting is an important component of treatment for hand infections because it allows the soft tissues to rest.
When more aggressive treatment is required
If there is:
- Failure of an oral antibiotic trial
- Lymphangitis with erythematous streaking
IV antibiotics may be required.
3. Acute Paronychia
Paronychia is an infection of the nail fold.
Clinical features
- Erythema
- Tenderness
- Swelling
- Possible visible purulence underneath the eponychial fold
Staphylococcus aureus is the most common organism.
Early paronychia without pus
Treatment:
- Oral antibiotics
- Warm soaks
Paronychia with visible pus
Drainage is usually required.
Possible methods include:
- Hypodermic needle
- Scalpel
- Freer elevator underneath the eponychial fold
- Small incision along the eponychial fold
If there is fluid underneath the nail plate, a portion of the nail plate may need to be removed to achieve adequate decompression.
4. Chronic Paronychia
Chronic paronychia is different from acute bacterial paronychia.
It is commonly associated with fungal organisms, including:
- Candida
- Trichophyton
Atypical mycobacteria and gram-negative bacteria should also be considered.
Treatment
If confined mainly to the nail plate:
- Topical antifungal treatment
With chronic induration and separation of the nail fold:
- Nail plate removal may be required
- Marsupialization may be required in resistant cases
5. Felon
A felon is a subcutaneous abscess involving the fingertip pulp.
The pulp is a poorly compliant compartment containing multiple fibrous septa.
Why it matters
The closed compartments can develop high pressure, resulting in:
- Tissue compromise
- Skin necrosis
- Extension to bone
- Extension to the flexor tendon sheath
A preceding penetrating injury is common.
Organisms
- Staphylococcus aureus
- Increasing prevalence of MRSA
Treatment
Drainage is required for an established abscess.
The important surgical principles are:
- Adequately decompress the pulp
- Break up the fibrous septa
- Avoid injury to neurovascular structures
- Avoid violating the flexor tendon sheath
- Avoid extending proximally toward the DIP flexion crease
A mid-axial incision is commonly used.
6. Herpetic Whitlow
Herpetic whitlow is caused by:
- HSV-1
- HSV-2
Clinical features
- Clear vesicles
- Vesicles may coalesce and ulcerate
- May become secondarily infected
Important exam point
Incision and drainage is contraindicated.
Diagnosis can be confirmed when necessary with appropriate viral testing, and treatment commonly includes:
- Acyclovir
- Dry dressing
7. Pyogenic Flexor Tenosynovitis
This is an infection of the closed flexor tendon sheath.
It commonly follows direct trauma.
Kanavel’s Cardinal Signs
Remember the four classic findings:
- Flexed posture of the digit
- Tenderness along the flexor tendon sheath
- Severe pain with passive extension
- Fusiform swelling of the digit
The fusiform swelling is often described as a sausage digit.
Treatment
If symptoms have been present for less than 24 hours, a trial of:
- IV antibiotics
- Splinting
- Elevation
may be considered.
If there is no improvement within 24 hours, surgery is indicated.
Presentation after more than 24 hours generally requires:
- Surgical irrigation
- Debridement
- Decompression of the flexor sheath
8. Human Bite
Also called a fight bite.
Typically involves:
- Third or fourth MCP joint
The tooth can penetrate:
- Extensor tendon
- Joint capsule
- Metacarpal head
Therefore, these injuries should be considered potentially open joint injuries.
Treatment
- Surgical irrigation and debridement
- Exploration of the joint
- Leave the wound open
- Preserve the sagittal bands
Common organisms include:
- Staphylococcus
- Beta-hemolytic Streptococcus
- Eikenella
9. Animal Bites
The most common animal bites are from:
- Dogs
- Cats
- Rodents
Dog bites
They usually produce more:
- Crushing
- Tearing
and have a lower infection rate than cat bites.
Cat bites
Cat bites have a much higher risk of infection because the sharp teeth produce:
- Small puncture wounds
- Deep penetration
- Rapid sealing of the wound
This can result in a deep abscess.
Pasteurella is an important organism in animal bites. Animal bites are frequently polymicrobial.
10. Deep Space Infections of the Hand
Important deep spaces include:
- Dorsal subaponeurotic space
- Thenar space
- Midpalmar space
- Hypothenar space
- Adductor space
- Web spaces
These infections may occur through:
- Direct penetrating trauma
- Spread from adjacent infected structures
11. Thenar Space Infection
The thenar space lies deep to the long flexor tendons of the index finger.
It may result from:
- Contiguous spread
- Penetrating trauma
Clinical findings may include an abducted thumb posture.
Treatment commonly involves drainage through:
- Volar incision
- Dorsal longitudinal incision
Avoid transverse incisions across the web space because of the risk of contracture.
12. Midpalmar Space Infection
The midpalmar space lies:
- Dorsal to the long flexor tendons of the middle, ring and little fingers
- Volar to the interossei
Clinical features
- Loss of the normal concavity of the palm
- Pain with direct palpation
- Pain with passive movement of the middle and ring fingers
Treatment depends on the extent of infection and requires appropriate drainage.
13. Web Space Infection
Also called a collar-button abscess.
It may begin as:
- Infected blister
- Open wound
- Palmar callus
The infection can extend from the palmar to the dorsal aspect of the hand.
Treatment
Often requires:
- Palmar incision
- Dorsal incision
Avoid transverse incisions in the web space because of the risk of contracture and painful scarring.
14. Necrotizing Fasciitis
This is a surgical emergency.
A common causative organism is:
Group A Streptococcus
Clinical clues
- Severe tenderness extending beyond the erythematous area
- Significant edema
- Crepitus
- Subcutaneous gas
- Fever
- Tachycardia
- Hypotension
At surgery, the tissue may contain gray, liquefied fat with characteristic “dishwater pus.”
Treatment
Requires:
- Urgent surgical debridement
- Often repeated debridements at 24 to 48-hour intervals
- Amputation may occasionally be necessary
Delay can result in sepsis, organ failure, limb loss or death.
15. Septic Arthritis of the Hand
Possible causes include:
- Penetrating trauma
- Hematogenous spread
- Contiguous spread
Common organisms:
- Staphylococcus aureus
- Beta-hemolytic Streptococcus
In sexually active patients, consider:
- Neisseria gonorrhoeae
Important differential diagnosis
A warm, swollen joint is not always septic arthritis.
Consider:
- Gout
- CPPD
- Calcific tendinitis
Joint aspiration
When aspiration is performed, send for:
- Gram stain
- Culture
- Crystal analysis
16. Chronic Hand Infections
Important chronic infections include:
Tuberculosis
May involve the flexor sheath and may produce:
- Rice bodies
- Caseating granulomas
Mycobacterium marinum
Think of:
- Marine exposure
- Fish-hook injury
- Aquarium or water-related exposure
It may require special culture conditions and can produce non-caseating granulomas.
Cat-scratch disease
Caused by Bartonella.
Typically:
- Self-limiting
- Associated with lymphadenopathy
- Diagnosis can be supported by serology
Tularemia
Think of:
- Rabbit exposure
- Ulcerating papule
- Lymphadenopathy
Actinomycosis
A classic clue is:
Yellow sulfur granules
17. Fungal Infections
Fungal infections may be:
- Cutaneous
- Subcutaneous
- Deep
Diagnosis may involve KOH examination.
Sporotrichosis
Classic history:
- Gardener
- Florist
- Thorn injury
Characteristic finding:
Multiple nodules along the lymphatic drainage pathway.
Surgery is generally not curative, although biopsy may be performed to establish the diagnosis.
High-Yield Exam Points
| Condition | Key clue | Key treatment/concept |
|---|---|---|
| Cellulitis | No abscess | Antibiotics, splint, elevation |
| Acute paronychia | Nail-fold infection | Antibiotics/warm soaks; drain pus |
| Chronic paronychia | Chronic fungal/inflammatory process | Topical antifungal; nail removal/marsupialization when needed |
| Felon | Pulp-space abscess | Drain and decompress septa |
| Herpetic whitlow | Clear vesicles | Do not incise |
| Pyogenic flexor tenosynovitis | Kanavel signs | Early IV antibiotics or urgent surgical drainage |
| Fight bite | 3rd/4th MCP | Surgical irrigation and debridement |
| Cat bite | Deep puncture, high infection risk | Consider polymicrobial infection |
| Thenar infection | Abducted thumb | Drainage |
| Web-space infection | Collar-button abscess | Palmar and dorsal drainage |
| Necrotizing fasciitis | Severe pain, crepitus, systemic toxicity | Emergency debridement |
| Septic arthritis | Warm swollen joint | Aspiration, culture and appropriate surgical treatment |
| M. marinum | Marine exposure | Special culture considerations |
| Sporotrichosis | Thorn injury + lymphatic nodules | Usually medical treatment |
The most important exam pattern
When confronted with a hand infection question, pay particular attention to:
Organism + type of exposure + duration + anatomical compartment + presence or absence of pus + systemic features.
These clues often determine both the diagnosis and the treatment.
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