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The Best in FOAM Education

  • Sean Boaglio, DO

Watch out for the Smooth Criminal: The Dirty Felon

A 30 year old male presents to the ED after a crush injury to his right thumb 1 month ago. Originally, there were small areas of skin break but they have now healed. Over the past three days, he has experienced progressive pain, swelling, and erythema to the pulp of the right thumb over the past three days.

Work Up

  • XR: No foreign body, soft tissue swelling pulp of thumb

  • US: Fluid collection to pulp of thumb visualized with water bath technique

  • Digital Nerve Block: Thumb cleaned with chlorhexidine. Transthecal Nerve Block, Alternative 3-sided pattern, 1% Lidocaine

  • I/D of Felon: Latex glove finger tourniquet applied. #11 blade, Bilateral Longitudinal approach “through and through”. Pus easily expressed. Irrigated with angiocatheter on saline flush. Septations broken up with hemostat blunt dissection. Strip of iodoform packing gauze passed through. Tourniquet removed. Wrapped. First dose of Cephalexin and Bactrim

  • Disposition: Discharge home. Follow up in Hand Clinic or ED. Return in 1-2 days.

Take Away #1

  • Do NOT incise and drain a Herpetic whitlow. Herpetic will cause fingertip pain but should not cause taut erythema.

  • Use waterbath and ultrasound to visualize Felon. Water is excellent acoustic window and the US probe is waterproof.

Take Away #2

Digital Block

  • Transthecal Block “Flexor Tendon block”: one injection, same efficacy as 3-sided or Ring block.

  • Insert needle 90 degree angle at MCP joint, hit bone, retract slightly and inject. Tip: apply proximal pressure with your finger to direct flow of lidocaine distally.


  • Do not cross DIP to avoid flexure contracture. Digital arteries and nerves arborize near DIT. Aim to start incision 5 mm distal to DIP to avoid these structures.

  • Bilateral or Unilateral Longitudinal approach preferred.

  • Avoid “fishmouth” technique as can cause unstable painful fingertip.

  • To avoid non-pressure bearing side of digit, incision should be made along the ulnar aspect of the index, middle, and ring fingers and along the radial aspects of the thumb and little finger, bilateral if needed for drainage.

  • Some controversy but others favor longitudinal midline incision as it avoids the neurovascular bundle.

Take Away #3

  • Most common organism is MRSA. Cover for staph and strep.

  • Cephalexin 500mg QID 7 -10 days AND

  • TMP/SMX DS q12H 7-10 days OR

  • Doxycycline 100mg BID OR

  • Clindamycin 450mg TID 7-10 days

If untreated or treated incorrectly can progress to osteomyelitis. Iatrogenic complication of drainage can be Flexor Tenosynovitis. Patient should follow up for drain/packing removal in 2 days.


Sean Boaglio, DO is a current third year resident at Stony Brook Emergency Medicine.


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