Hand infection

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Infections frequently occur in the hand and wrist. Because the hand is heavily used for contact with the world, it is vulnerable to cuts, punctures, scrapes, and other traumas (both major and trivial) that may violate the skin barrier. In some circumstances, infections in the hand and wrist may be due to spread via the blood from remote locations such as the heart. People with impaired immune systems (HIV, cancer, poorly-controlled diabetes) are more vulnerable to these infections and may be suffer infections that might otherwise not occur in those with a normal immune system.

A major point to distinguish among the hand infections is the presence or absence of pus. If a collection of pus (also called an abscess) exists, antibiotics alone cannot cure the infection; the pus must be adequately drained before the infection will resolve. After drainage of pus, the incision is left open to avoid reaccumulation of pus.

Physical examination is usually the best way to determine if/where a collection of pus resides in the hand. Patients being evaluated for a possible hand infection will often undergo x-rays, which may show air under the skin and/or changes in the bone. More sophisticated studies, such as MRI and ultrasound, are also available, but are usually not necessary if physical examination provides the diagnosis.

ICD-9 codes are noted for all diseases listed below. The ICD-9 system categorizes infections based on geographic area of the body (e.g. finger, wrist, forearm, etc). ICD-9 codes do not distinguish the specific location of an infection within the hand (e.g. nailbed, joint, flexor tendon sheath). As such, the same code may be used to describe multiple infections that may be treated quite differently from each other.

Common bacteria

Most hand infections are caused by bacteria in the environment gaining access through the skin via a violation of the skin. As such, it is not surprising that Streptococcus and Staphylococcus (Strep and Staph) are the most common organisms found in these infections. [Houshin S, Seyedipour S, Wedderkopp N. Epidemiology of bacterial hand infections. International Journal of Infectious Diseases. 2006; 10: 315-9.] Other bacteria may cause infection depending on its cause: "Eikanella" may occur in the setting of a human bite; Pasteurella may occur in the setting of dog and cat bites.

Common antibiotics

Antibiotics are usually employed to treat hand infections. An ideal antibiotic is cheap, effective, taken infrequently (one or two times per day), and able to be given by mouth.

For most infections, antibiotics effective against Staph and Strep are chosen. [Cornwall R, Bednar MS. Infections. In: Trumble TE. Hand Surgery Update 3. Rosemont, IL: American Society for Surgery of the Hand: 2003: 433-57.] Penicillinase-resistant penicillins (methicillin, dicloxacillin, etc.) or first generation cephalosporins (cephalexinCefalexin, cefadroxilCefadroxil) are commonly used. Recent increases in MRSA (a drug resistant Staph bacteria), have caused concern that these antibiotics may not be effective for many patients. [Bach HG, Steffin B, Chhadia AM, Kovachevich R, Gonzalis MH. Community-associated methicillin-resistant Staphylococcus aureus hand infections in an urban setting. J Hand Surg [Am] . 2007; 32: 380-3.] For these settings, doctors often choose antibiotics that MRSA is less likely to be resistant to such as clindamycin, trimethoprim/sulfaCo-trimoxazole combinations (Bactrim, Septra), and quinolones (ciprofloxacin, levofloxacin). The choice of a particular antibiotic depends on where in the world the patient lives (affects antibiotic resistance and availability to patients) and where in the body the infection is occurring (antibiotics differ in their ability to reach certain body areas).

Cellulitis (ICD-9 681.00)

Cellulitis is a bacterial infection of the dermis (deep layer of the skin) and subcutaneous tissue. Cellulitis causes by certain bacteria may be referred to by an eponym, such as erysipelas for cellulitis caused by Streptococcus. A patient with cellulitis does not have a collection of pus. As such, no surgical drainage is necessary; antibiotics, rest, and elevation of the affected hand are used as treatment. When oral antibiotics fail and/or the patient otherwise appears systemically, ill, intravenous antibiotics may be used. Treatment of cellulitis is usually performed by medical doctors rather than surgeons.

Paronychia (ICD-9 681.02)

Paronychia is an infection of the skin folds that sit over the fingernail. [Jebson PJ. Infections of the fingertip. Paronychias and felons. Hand Clinics. 1998; 14: 547-55.] Common causes include aggressive manicuring and nail biting. A collection of pus is present and resides between the surface of the fingernail and the overlying skin fold. Symptoms include pain, redness, and swelling of the nail fold. In advanced cases, the infection may involve the nail fold all the way around the edge of the fingernail. Treatment is with drainage, local wound care, and antibiotics. Drainage may be performed by separating the nail fold from the fingernail or by cutting through the skin of the nail fold. Only rarely, or if initial drainage fails to resolve the infection, is removal of part or the entire fingernail necessary.

Herpetic whitlow (ICD-9 054.6)

Unlike the other infections that will be discussed in this entry, herpetic whitlow [Gill MJ, Arlette J, Buchan KA. Herpes simplex virus infection of the hand. A profile of 79 cases. Am J Med. 1988; 84(1): 89-93.] is a viral illness. It is a self-limiting infection caused by a herpesvirus. Symptoms include redness and mild swelling at the base of the nailfold. Often small blisters filled with clear fluid, called vesicles, will occur in this location. This disease classically occurred in dental hygienists and other healthcare providers. Whitlow is not an abscess, and is not a bacterial infection. As such, neither surgical drainage nor antibiotics are necessary or appropriate. The disease typically goes away without treatment within two weeks.

Felon (ICD-9 681.01)

Felon is an infection of the pad of the finger. A puncture wound (usually trivial, such as a splinter or thorn) is the most common cause. Multiple septae (firm soft tissue attachments) pass from the bone of the distal phalanx (bone of the fingertip) to the skin on the palm side. These ligaments help support the skin in position and assist with fine grasp and pinching. In a felon, an abscess forms between these septae. Symptoms include pain, swelling, and redness over the pad of the finger. Again, treatment is with drainage, local wound care, and antibiotics

Subcutaneous abscess (ICD-9 681.00 fingers, 682.4 hand/wrist)

The skin on the dorsum (back side) of the fingers and hand has no attachments to deeper structures (in contrast to the palm side, see Felon, above). As such, a collection of pus can form under the skin on the dorsal hand and/or fingers just as it can in other areas of the body. Symptoms include pain, swelling, redness (typically most intense right over the pus collection). Treatment is with drainage, local wound care, and antibiotics.

For all of the three infections listed above (paronychia, felon, and subcutaneous abscess), treatment is usually provided by an emergency room physician or a primary care physician. Drainage is usually performed under local anesthesia, and the patient is usually sent home on oral antibiotics. If initial treatment fails, the initial treating physician may choose to consult a hand surgeon.

For the infections listed below, the patient is most commonly treated in an operating room under general anesthesia by a hand surgeon. After the initial surgical drainage, the patient is typically admitted to the hospital for intravenous antibiotics and local wound care (which may require the assistance of a nurse and/or therapist).

Septic arthritis (ICD-9 682.4)

All joints of the hand and wrist have a soft tissue shell around them, called a capsule. This capsule keeps synovial (joint lubricating) fluid within the joint space. In order for a joint to be mobile, the cartilage surfaces within the joint must be able to glide past each other. When bacteria enter the joint and cause infection (septic arthritis), they may release chemicals, called exotoxins, which destroy the gliding surfaces within the joint and impair recovery of joint motion.

Infections reach a joint space by two main routes. In younger, healthier people, bite wounds are a frequent route of entry (e.g. punching someone in the mouth may cause a tooth to puncture the hand at the metacarphophalangeal joint (big knuckle) of a finger). In hospitalized or sicker patients, infection may start in another part of the body (such as endocarditis) and spread via the blood to the hand and/or wrist joint(s).

Symptoms include pain, swelling, and redness over the affected joint. The joint is typically stiff, and the patient complains of severe pain with attempts to move the joint. Axial loading (pushing the two bones of the joint toward each other) also causes pain.

Surgical approach for joint drainage depends on which joint is involved, and what other structures are nearby (such as tendons, nerves, blood vessels). Both open and arthroscopic techniques have been described.

Flexor tenosynovitis (ICD-9 681.00)

A series of pulleys hold the flexor tendons against the finger on the palm side of the hand. The first of these is in the palm over the head of the metacarpal bone; the last is at the base of the distal phalanx. The inner surface of these pulleys acts as a gliding layer, allowing the flexor tendons to move past during finger flexion and extension. In flexor tenosynovitis [Boles SD, Schmidt CC. Pyogenic flexor tenosynovitis. Hand Clin. 1998; 14: 567-78.] , a collection of pus develops between these pulleys and the flexor tendons. As with joint space infections, bacterial exotoxins may destroy this gliding layer and impair motion recovery of the finger.

Four classic signs of flexor tenosynovitis were described by Allan Kanavel [Kanavel AB. The treatment of acute suppurative tenosynovitis—discussion of technique. In: Infections of the hand; a guide to the surgical treatment of acute and chronic suppurative processes in the fingers, hand, and forearm. 5th ed. Philadelphia: Lea and Farbinger: 1925: 985-90.] :
# Partially flexed posture of the finger (or thumb)
# Pain with passive finger extension over the palm side of the finger
# Pain to touch over the palm side of the finger
# Fusiform (circumferential) swelling along the entire length of the finger

Treatment is with early drainage and antibiotics. Hand therapy is usually needed after surgery in order to regain finger motion.

Extensor tenosynovitis, as an infection, does not exist. There are no pulleys over the back of the finger. Extensor tenosynovitis may be used to describe an inflammatory (not infectious) tendon problem where the extensor tendons pass through pulleys over the wrist. DeQuervain's syndrome is an example of this.

Web space abscess (ICD-9 682.4)

The soft tissue at the base of two adjacent fingers where they enter the palm is called the web space. This tissue must be mobile enough to allow the fingers to spread apart, and compressible enough that bringing the fingers together does not cause excessive bulk. Between the skin on the palmar and dorsal sides in the web space are support structures called natatory ligaments. These exist in a mesh-like configuration, separating the palmar and dorsal subcutaneous areas in the web space.

If the palmar or dorsal subcutaneous space develops an infection, this can spread through the natatory ligaments to create abscesses in the dorsal and palmar subcutaneous spaces of the web and connected through the natatory ligaments. Because of this shape of the abscess, a web space infection has also been called a collar button abscess or a dumbbell abscess. Drainage is performed from the palm side and dorsal side in order to address both pus collections.

Other hand infections

Additional potential spaces exist within the hand which can become infected. These areas include the: thenar space (along the muscles at the base of the thumb), midpalmar space (between the bones and the tendons/blood vessels in the palm), and hypothenar space (along the muscles on the small finger side of the hand). These infections are relatively rare. Cause is usually due to puncture wounds, but may also be due to spread of infections from nearby locations. Treatment is with surgical drainage.

Other infecting organisms

Most infections of the hand are caused by bacteria that are present in the environment (Staphylococcus and Streptococcus) or objects that can penetrate the skin (Eikanella and Pasteurella on the teeth of humans and dogs/cats, respectively). Certain geographic regions may have other organisms (such as Mycobacteria and fungi) in the local environment that may cause infections. Also, characteristics of the person getting infected (most notably immune status), may allow for less common organisms to cause infection. Diabetic patients, for example, more frequently have hand infections involving two or more bacteria, and involving bacteria other than Staph and Strep. [Kour AK, Looi KP, Phone MH, et al. Hand infections in patients with diabetes. Clin Orthop Relat Res. 1996; 331: 238-44.]

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