Hand Infections
Summary
Infections of the hand are unique because the hand contains multiple closed, non-distensible compartments (pulp space, tendon sheaths, deep palmar spaces). Infection here causes rapid pressure rise, leading to compartment syndrome, tissue necrosis (tendon/bone), and permanent stiffness. Prompt diagnosis and often surgical intervention are required to preserve function. [1,2]
Key Facts
- Paronychia: Infection of the nail fold (Most common).
- Felon: Infection of the pulp space of the fingertip. The pulp contains vertical septae that anchor the skin to the periosteum; swelling here causes tamponade of vessels and osteomyelitis of the distal phalanx.
- Pyogenic Flexor Tenosynovitis: Infection within the synovial sheath of the flexor tendon. It destroys the gliding mechanism and blood supply (vincula) within hours/days.
Clinical Pearls
Kanavel's Cardinal Signs: Used to diagnose Flexor Tenosynovitis. > 1. Tenderness along the tendon sheath (not just the joint). > 2. Fusiform swelling ("Sausage finger"). > 3. Finger held in semi-flexion (to maximise volume). > 4. Pain on passive extension: The earliest and most sensitive sign. Extending the finger stretches the inflamed sheath causing excruciating pain.
The "Fight Bite": A laceration over the MCP joint (knuckle) must be assumed to be a human bite (tooth injury from punching a mouth) until proven otherwise. Eikenella corrodens is the specific organism. Treat with Co-amoxiclav. Never close these wounds primarily.
The "Little Finger & Thumb Connection": The tendon sheath of the Little Finger communicates with the Ulnar Bursa. The Thumb communicates with the Radial Bursa. These two bursae connect at the wrist ("Horseshoe Abscess"). Therefore, an infection in the little finger can spread rapidly to the thumb and forearm ("Space of Parona"). The middle three fingers usually have isolated sheaths.
Microbiology
- Staphylococcus aureus: Most common (60-80%).
- Streptococcus: Spreading cellulitis.
- Pasteurella multocida: Cat/Dog bites (rapid onset less than 24h).
- Eikenella corrodens: Human bites ("Clenched fist injury").
- Pseudomonas: Nail infections (green nail).
- HSV: Herpetic Whitlow (Dentists/Nurses). Vesicular.
Anatomy
- Pulp Space: Compartmentalised by fibrous septae.
- Tendon Sheaths: Synovial tunnels containing nutrient fluid. Bacteria thrive here, and pressure kills the tendon.
- Deep Spaces: Thenar, Hypothenar, and Mid-palmar spaces.
Symptoms
History
- Look: Localise the point of maximal swelling.
- Feel: Test for fluctuance (pus). Assess sensation (digital nerve compression).
- Move: Test Kanavel's signs (Passive extension).
- Lymphatics: Check for tracking lymphangitis and epitrochlear/axillary nodes.
Imaging
- X-Ray: Mandatory for bites/trauma. Look for:
- Foreign bodies (glass/tooth fragment).
- Gas in tissues (Necrotising fasciitis).
- Osteomyelitis (bony destruction).
- Fracture.
Labs
- Swab: If discharging.
- FBC/CRP: Systemic response.
- Blood Glucose: Exclude undiagnosed diabetes.
Management Algorithm
HAND INFECTION
↓
ASSESS SEVERITY
┌───────────┴───────────┐
MILD SEVERE / DEEP
(Cellulitis only) (Abscess / Tenosynovitis)
↓ ↓
ORAL ABX ADMIT + ELEVATE
(Flucloxacillin (Bradford Sling)
or Co-amoxiclav) IV ANTIBIOTICS
+ Review 24h KEEP NBM
↓
SURGICAL DRAINAGE
(If pus / Tenosynovitis)
1. General Measures
- Elevation: The hand must be elevated in a high arm sling (Bradford sling) to reduce oedema. "Hand above Heart".
- Splinting: Position of safety (MCPs flexed 90°, IPJs extended).
- Tetanus: Check status.
2. Antibiotics
- Standard: IV Flucloxacillin.
- Bites: IV Co-amoxiclav (covers Anaerobes + Eikenella/Pasteurella).
- Penicillin Allergy: Clindamycin or Clarithromycin + Metronidazole.
3. Surgical Intervention
- Paronychia: Incise the nail fold or remove part of the nail.
- Felon: Longitudinal incision (avoid "fish-mouth" incisions which cause sensory loss/instability).
- Tenosynovitis:
- Catheter Irrigation: Proximal and distal incisions. Insert catheter. Flush saline through the sheath.
- Open Washout: If prolonged/severe.
- Bites: Formal debridement and washout. Leave wound open.
- Stiffness: The enemy of the hand surgeon. Early mobilisation essential once infection controls.
- Tendon Necrosis/Rupture: Loss of function.
- Osteomyelitis.
- Amputation.
- Paronychia: Excellent.
- Tenosynovitis: 10-20% usually have some permanent stiffness.
- Diabetics: Significantly worse outcomes.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Hand Infections | BSSH (UK) | Early referral to specialist hand unit. IV Abx first line. |
| Bite Wounds | BAPRAS | Antibiotics for all human/cat bites. Don't close primarily. |
Landmark Evidence
1. Kanavel (1912)
- Allen B. Kanavel wrote the seminal textbook on hand infections. His anatomical descriptions of the fascial spaces and cardinal signs remain the gold standard today.
Why is a hand infection so serious?
The hand is a very complex machine packed with moving parts (tendons) inside tight tunnels. Infection causes swelling, and because the tunnels can't stretch, the pressure builds up and crushes the blood supply to the tendons. This can permanently damage the hand function.
What is the treatment?
You need strong antibiotics into a vein and you must keep your hand high up in a sling to help the swelling drain. If there is pus or infection in the tendon tunnel, we need to operate to wash it out.
Why can't you stitch my bite wound?
Animal and human mouths are full of bacteria. If we stitch the wound closed, we trap the bacteria inside, creating an abscess. We leave it open to heal from the bottom up.
Primary Sources
- British Society for Surgery of the Hand (BSSH). Hand Injuries and Infections Standards of Care.
- Kennedy CD, et al. Pyogenic Flexor Tenosynovitis. Orthop Clin North Am. 2017.
- Osterman M, et al. Acute Hand Infections. J Hand Surg Am. 2014.
Common Exam Questions
- Diagnosis: "4 Cardinal Signs?"
- Answer: Kanavel's Signs (Tenderness, Swelling, Flexion posture, Pain on extension).
- Microbiology: "Organism in human bite?"
- Answer: Eikenella corrodens.
- Treatment: "Antibiotic for cat bite?"
- Answer: Co-amoxiclav (Flucloxacillin is inactive against Pasteurella).
- Anatomy: "Little finger spreads to?"
- Answer: Thumb/Wrist (via Ulnar Bursa -> Space of Parona -> Radial Bursa).
Viva Points
- Herpetic Whitlow: Warning! Do NOT incise this. It is a viral infection (HSV). Incision can spread it or cause bacterial superinfection. Diagnosis is clinical (vesicles/blisters) + viral swab. Treat with Acyclovir and covering it.
- Collar Stud Abscess: An abscess in the web space that has two components (volar and dorsal) connected by a narrow tract (like a collar stud). You must drain both sides.
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.