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Hand infections and pyogenic flexor tenosynovitis
Hand infection spreads quickly in closed spaces and tendon sheaths; pyogenic flexor tenosynovitis, recognised by the four Kanavel signs, and a fight bite over an MCP joint are emergencies that need intravenous antibiotics and surgical washout.
Why it matters in the exam
Questions present a swollen, painful finger after a small injury, a bite or a wound over a joint, and ask for the type of infection and its urgency. In pyogenic flexor tenosynovitis the four Kanavel signs appear: uniform swelling of the whole finger (sausage digit), a finger held in slight flexion, tenderness along the tendon sheath, and severe pain on passive extension — the earliest and most sensitive sign. Treatment is intravenous antibiotics and surgical irrigation of the sheath; only in very early cases can antibiotics alone be tried with close follow-up. A fight bite is a small cut over the MCP joint after a punch to the teeth: it looks harmless, but mouth bacteria enter the joint and tendon, and when the fist opens the skin wound moves and hides the damage. Treatment is exploration and washout in theatre, no suturing, and antibiotics covering mouth bacteria such as Eikenella corrodens (for example amoxicillin-clavulanate). A cat bite carries a high risk of Pasteurella multocida infection because thin teeth penetrate deeply. Common superficial infections are paronychia around the nail, drained when there is pus, and a felon — an abscess of the fingertip pulp that needs drainage. In contrast, a herpetic whitlow with vesicles is not drained and is treated with an antiviral drug. In every hand infection, check tetanus cover, mark the edge of the redness, obtain radiographs to exclude a foreign body and elevate the hand.
Key points
- The four Kanavel signs — pyogenic flexor tenosynovitis, an emergency.
- Pain on passive extension is the earliest and most sensitive sign.
- Fight bite — mouth bacteria and Eikenella; washout without suturing.
- Cat bite — Pasteurella; amoxicillin-clavulanate.
- Herpetic whitlow — do not incise.
Summary table
| Infection | Identifying finding | Common organism | Treatment |
|---|---|---|---|
| Pyogenic flexor tenosynovitis | The four Kanavel signs; pain on passive extension | Staphylococcus aureus and streptococci | Intravenous antibiotics and surgical washout |
| Fight bite over MCP | Small cut over a joint after punching teeth | Mouth bacteria, Eikenella corrodens | Exploration and washout, no suturing, amoxicillin-clavulanate |
| Cat bite | Deep puncture wounds | Pasteurella multocida | Amoxicillin-clavulanate, close follow-up |
| Paronychia and felon | Pus around the nail or in the fingertip pulp | Staphylococcus aureus | Drainage and antibiotics as needed |
| Herpetic whitlow | Clear vesicles on the finger | Herpes virus | No incision; antiviral treatment |
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Sources
- Green's Operative Hand Surgery, 8th ed. (2022) — Acute Infections of the Hand
- IDSA Practice Guidelines, 2014 — Diagnosis and Management of Skin and Soft Tissue Infections (bite wounds)
Sources are given for further reading; the text is written afresh and not copied from them.
Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.