Hand infections are a common presentation, they can spread rapidly and cause damage to local structures and therefore require prompt identification and treatment.

Causes

Hand infections can be the result of a penetrating injury (e.g. splinter, rose thorn), bites (animal or human), contiguous spread from an adjacent structure or there may be no identifiable trigger.

Hand infections are more common in people with diabetes, smokers, or the immunocompromised. The most common organism is staphylococcus aureus, followed by streptococcus species.

Investigations

• A wound swab should be taken to identify causative pathogen and ensure appropriate antibiotic choice
• X-rays should be requested if there is a history of trauma to look for fractures, foreign bodies or evidence of osteomyelitis
• Routine bloods including WCC and CRP can aid diagnosis.

Management

• Areas of erythema should be marked to monitor spread and advice should be given to elevate the hand
• Most superficial hand infections can be managed as an outpatient with oral antibiotics
• More severe or deep hand infections may require admission for intravenous antibiotics +/- surgery.

Common Hand Infections

Paronychia

A paronychia is an infection of the skin fold surrounding the nail. It usually occurs from trauma such as nail biting. It is the most common infection of the hand. It presents as a painful erythematous swelling surrounding the nail plate. Treatment is usually with oral antibiotics. If there is a collection of pus, this will require incision and drainage. In severe cases the nail plate may need to be removed to allow sufficient drainage of pus.

Figure 1: An acute paronychia in a left ring finger. A collection of pus is visible around the radial paronychium and eponychium and there is surrounding inflammation and erythema (Image source: https://www.aafp.org/pubs/afp/issues/2017/0701/p44.html)

A chronic paronychia may develop in those exposed to wet environments such as dishwashers. It is usually caused by infection with Candida albicans and should be considered in those who don’t respond to oral antibiotics.

If left untreated, paronychia can lead to necrosis of the surrounding skin or nail bed and osteomyelitis.

Felon

A felon is an infection of the pulp of a digit. It is usually the result of a penetrating injury e.g. splinter or blood glucose needlestick or it may spread locally from a paronychia.

Figure 2: A felon of the thumb (image source: https://www.orthobullets.com/hand/6102/felon)

In the finger pulp, fibrous septae attach bone to skin creating multiple small compartments. Swelling from infection or abscess formation causes a pressure rise within these compartments, leading to extreme pain, and if left untreated, ischaemia and necrosis. Most cases are treated with oral antibiotics. If an abscess has developed this will need incision and drainage.

Flexor Sheath Infection

Flexor sheath infection is an infection of the synovial sheath that surrounds the flexor tendon. It is usually caused by inoculation from a penetrating injury such as a rose thorn, but it can be the result of local spread from a felon.

When assessing a patient presenting with a hand infection, it is important to assess for the 4 Kanavel’s signs

1. Tenderness on palpation of the flexor tendon
2. Fusiform swelling
3. Finger held in fixed flexion
4. Pain on passive extension

Figure 3: A flexor sheath infection in the right index finger (image source https://bjgp.org/content/69/683/315)

Treatment is a washout in theatre and antibiotics. A flexor sheath infection is a surgical emergency. Delayed treatment can lead to rapid spread, stiffness and tendon rupture.

Hand Infections, When to refer?

Paronychia’s and felons are common presentations to ED and GP. Most are uncomplicated and can be managed with oral antibiotics and safety netting for spread or worsening of infection.

If there is a visible or palpable collection, this should be referred to plastic or hand surgeons for incision and drainage. In a paronychia, they may wish to remove the nail plate to aid with drainage of infection.

If the patient has not improved with oral antibiotics, if they are vulnerable to infection (e.g. immunocompromised), if there is any sign of proximally spreading or worsening infection, or if there is any sign of systemic infection (fevers, tachycardia), the patient may need intravenous antibiotics and should be referred to plastic or hand surgeons for assessment and/or admission.

A flexor sheath infection is a surgical emergency. If there is any concern for flexor sheath infection, an urgent referral to plastic or hand surgeons should be made.

References/Further Reading

Moran TE, Freilich AM. Hand Infection. 2023 Aug 8. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2024 Jan–. PMID: 32496729.

Rerucha CM, Ewing JT, Oppenlander KE, Cowan WC. Acute Hand Infections. Am Fam Physician. 2019 Feb 15;99(4):228-236. PMID: 30763047.

Written by Ms Jennifer Mackay (CT2 Plastic Surgery) & reviewed by Miss Alexandra Sutcliffe (ST4 Plastic Surgery)