Flexor Sheath Infection

Flexor Sheath Infection

What you need to know:

Flexor sheath infections are a hand surgery emergency, delay in drainage can lead to necrosis of the flexor tendon and in the worse case scenario lead to amputation of the digit.

In the index, middle and ring fingers the flexor sheath extends from the distal interphalangeal joint in the digit to the palm. In the thumb and little finger the flexor sheath extends from the DIPJ / IPJ to the wrist, hence a flexor sheath infection in these digits may present as a horseshoe abscess.

Infection often occurs as a result of penetrating trauma (kitchen knife cutting an avocado, thorn whilst gardening).

Signs & Symptoms

    • Pain: usually over 24-48hrs
  • Kanavel signs of flexor sheath infection
    • Flexed posturing of the finger
    • Tenderness to palpating over the tendon sheath
    • Pain on passive extension
    • Fusiform swelling
    • Increased warmth and erythema of digit

Causative Organism: Staphylococcus aureus is the most common causative organism.

What you need to do:

Imaging generally not required.  If penetrating injury a radiograph may demonstrate a foreign body.  Ultrasound shows fluid the flexor sheath.  An MRI scan can be used to demonstrate extent of infection.  Have a high index of suspicion and explore surgically.


  • Nonoperative treatment may be indicated in a very early presentation.  This would consist of hospital admission with splinting of the hand, IV broad spectrum antibiotics as per local microbiology advice (IV 1.2g TDS Co-Amoxiclav), close observation. If no signs of improvement within 24 hours then surgery may be indicated.
  • Operative intervention is the mainstay of treatment.  Admission to hospital with emergent incision and drainage of flexor sheath.  Broad spectrum intravenous antibiotics should be administered as per local microbiology department advice (IV 1.2g TDS Co-Amoxiclav) following intraoperative cultures.

Operation Technique


    • GA or block
    • Arm Tourniquet
    • Remember digital nerves are superficial so careful dissection & identification
    • Transverse incision over A5 pulley DIP joint crease
    • Blunt dissection onto sheath with artery clip
    • Incise sheath
    • Swab any fluid discharged
    • Chevron incision in palm over A1 pulley (distal palmar crease) of affected finger finger
    • Digital neurovascular bundle at risk, identify and protect
    • Blunt dissection & incise sheath
    • A vertical split in the proximal aspect of A1 pulley can facilitate insertion of cannula into flexor sheath
    • Cannula into sheath and wash (water flows from proximal to distal). I find the following helpful to facilitate easier insertion of the cannula
      • Use a blunt tendon hook to lift FDS tendon
      • Place 20 gauge (pink) cannula between FDS and FDP
      • Left go of tendons and watch cannula slide into sheath
    • Wash with several litres normal saline
      • A bowl under the hand will keep the scrub team happy and save you from having a wet lap
    • Leave wounds open
    • Dress with on adhesive dressing, gauze, wool, crepe
    • Place in position of safety / Edinburgh splint
  • Post op
    • Elevate
    • Broad spectrum antibiotics until culture results are back
    • Wound check24-48hrs
    • May need to return to theatre

Further surgical tips for draining flexor sheath infections 

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