A 34-year-old female type one diabetic patient comes into your emergency department after several days of progressive swelling and severe pain of the right index finger tip. On your examination, the nail fold seems swollen and tender, but there is also some tenderness and tenseness of the pulp of the digit as well.
You wonder if you are dealing with a paronychia or a felon. Could it be both? What’s the optimal treatment for this first encounter? Antibiotics? Incision & drainage? Both?
Paronychias
A paronychia is an infection occurring just beneath the eponychial folds. It can occur on either the ulnar or radial side of the digit, or even extend like a horseshoe around the digit. Common culprits are nail fold trauma allowing the ingress of bacteria, such as manicures, nail biting, or even the application of artificial nails.
Like most soft tissue infections, the typical causative organism is usually Staphylococcus aureus. Community-acquired methicillin resistant Staphylococcus aureus (CA-MRSA) is certainly a consideration in this day and age in prevalent areas as well. Curiously more indolent paronychias are sometimes attributable to anaerobic infection, from oropharyngeal bacteria–this is thought to be due to one of the causative mechanisms (nail biting).
Treatment
Some advocate a trial of antibiotics and warm soaks for an early paronychia, rather than immediate incision and drainage. There is a dearth of evidence to support medical versus surgical management, but it’s generally accepted that when pus and fluctuance is present, it is prudent to get it out.
Ideally, incision and drainage should allow egress of the infection with minimal damage to the nail bed. This can be achieved by using an 11 or 14 blade scalpel to incise just above the nail bed, along the eponychial fold, without actually cutting through the eponychial skin itself. However in some more severe cases, elevation and even removal of the nail itself may be required.
Felons
A felon is an infection occurring within the compartments of the fingertip pulp. These compartments are septated and thus discrete. Infection within them causes intense pain and swelling of the fingertip that a patient usually will not ignore for long. More serious than your run-of-the-mill soft tissue infection, a felon has the potential to compromise blood flow to the distal fingertip through compression via edema from pus formation. Thus, urgent evaluation and treatment is paramount.
Felons are generally caused by penetrating trauma to the finger tip. This can include cuts, splinters, or even the seemingly benign needle stick of a glucose check for a diabetic patient. Another cause of felon is direct extension around the finger from a paronychia–thus one should consider incising the nail fold (as in the video above) as well when there is concern for both.
Treatment
Some advocate for a trial of antibiotics before incision and drainage for an early felon, as per this very brief evidence-based review. The antibiotic of choice would likely be a first generation cephalosporin given the likely culprit bacteria, Staphylococcus aureus–although I’d consider treatment for CA-MRSA as well with trimethoprim-sulfamethoxazole or vancomycin if the patient will be admitted to the hospital.
The line between what we call an abscess worthy of incision & drainage versus one that is early enough to be treated with antibiotics and watched is a little blurry. A patient may want to know the risks of deferring incision and drainage. Without terrifying your patient, it’s worthwhile to be knowledgable of the “worst case scenario” for a felon that progresses, as per this 2016 report of two patients who went on to develop necrosis of their fingertips requiring digital reconstruction.
So, you’ve decided to incise the felon. You’ve performed a digital block on the finger, the wound has been prepared with antiseptic, and you have your No. 11 blade scalpel in hand–now, where should you make the cut?
The internet and procedural textbooks are ripe with descriptions of different methods, as pictured above. Here’s my advice on where to place your incision, based on common-sense knowledge of the anatomy:
- The general guideline, as with any abscess, is to incise along the area of greatest tenderness and fluctuance. In the picture above, it’s happens to be a lateral incision. Coincidentally, this is considered a less morbid incision.
- More commonly (or when it’s tough to determine where the worst fluctuance is), a midline high longitudinal fat pad incision is another good choice. Keep in mind NOT to cut below the distal interphalangeal joint crease, which can lead to damage to the flexor tendon.
- Generally speaking, it is better to avoid transverse incisions, which have a higher risk of transecting digital nerves and arteries.
- Hockey-sticking or “fish-mouthing” may be needed for definitive treatment of a very severe felon, but can result in an unstable finger and compromise blood flow to the finger pulp. I’d defer these more radical procedure to the expertise of a hand surgeon and avoid them in the ED.
- Another more significant, but acceptable procedure for the more developed felon is the through-and-through incision and drainage, described in the video below.
Summary
Paronychias and felons are pesky finger tip infections that the everyday emergency and urgent care practitioner should expect to come across on a regular basis. A working knowledge of initial management options, incision and drainage techniques, and complications of the untreated infection is essential!