Flexor sheath infection (flexor tenosynovitis)
🖐️ About
- Flexor tenosynovitis is a surgical emergency involving infection of the flexor tendon sheath of the hand.
- If untreated, it can cause tendon necrosis, adhesions, disruption of the sheath, and permanent digital contracture.
- The closed tendon sheath acts as an ideal environment for rapid bacterial growth.
⚙️ Aetiology
- Most commonly caused by Staphylococcus aureus (including MRSA); Streptococcus species and Gram-negatives less common.
- Infection occurs in the closed synovial sheath, which is rich in nutrients but has poor host defence.
- Often secondary to penetrating trauma (e.g., puncture wound, bite, contaminated laceration).
- May spread via haematogenous seeding (rare).
🩺 Clinical: Kanavel’s Four Cardinal Signs
- 👉 Finger held in slight flexion (resting posture relieves tension).
- 👉 Fusiform (sausage-shaped) swelling of the digit.
- 👉 Tenderness along the course of the flexor tendon sheath.
- 👉 Severe pain on passive extension of the digit.
⚠️ The presence of all four Kanavel signs is highly suggestive of flexor tenosynovitis and should prompt urgent referral.
🔍 Differentials
- Cellulitis of the digit.
- Felon (pulp space abscess).
- Herpetic whitlow (HSV infection).
- Gouty tophus with secondary inflammation.
- Septic arthritis of the interphalangeal joint.
🧪 Investigations
- Bloods: FBC (↑ WCC), CRP, U&E, glucose (rule out diabetes).
- Blood cultures if systemic features present.
- X-ray: May exclude foreign body or bone involvement.
- Ultrasound/MRI: May demonstrate fluid in tendon sheath, but not usually needed before surgery.
💊 Management
- Urgent surgical intervention: Incision & drainage (I&D) or washout of the flexor sheath.
- IV antibiotics: Broad-spectrum initially (e.g., co-amoxiclav or cefuroxime + metronidazole); tailor according to cultures.
- Analgesia and elevation of the hand.
- Post-op physiotherapy to prevent adhesions and contractures.
- Delay in treatment can result in tendon necrosis, adhesions, loss of function, or amputation in severe cases.
📚 References
