Drainage of a Pulp Space Infection (Felon)
Drainage of a Pulp Space Infection (Felon)
Distal finger pulp space infections are the hand infections that most often require surgical drainage. Infection is usually caused by a penetrating injury to the pulp, an injury that may be quite trivial in itself. Superficial infections cause skin necrosis and point early, usually on the volar aspect of the pulp. Deeper infections are more likely to cause osteomyelitis of the underlying distal phalanx.
Depending on the depth of the infection, two different techniques exist for draining pus in this site:
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If the abscess is pointing in a volar direction in the distal pulp of the finger, as it commonly is, make a small incision on the lateral side of the volar surface and enter the abscess cavity obliquely. Midline incisions may produce painful scars.
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If the abscess is deep, the surgery described below may be necessary.
Position of the Patient
Place the patient on the operating table, with the arm lying on an arm board.
Incision
Make a straight incision on the lateral aspect of the terminal phalanx of the finger, extending to the tip of the finger close to the nail. The incision should not extend proximally to the distal interphalangeal joint; more proximal incisions may damage the digital nerve, causing a painful neuroma, or they may contaminate the joint with purulent material.
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Figure 5-74 Incision for drainage of pulp space infection (felon). The septa must be cut to ensure appropriate drainage.
The incision should be dorsal and distal to the distal end of the distal interphalangeal crease (Fig. 5-74). It should not extend distally beyond the distal corner of the nail. Avoid the ulnar aspect of the thumb and the radial aspect of the index and long fingers to avoid creating a scar that interferes with pinch.
Internervous Plane
There is no internervous plane in this incision. The skin incision lies between skin that is supplied by the dorsal cutaneous nerve and skin that is supplied by branches of the volar digital nerves.
Superficial Surgical Dissection
The pulp of the terminal phalanx contains numerous fibrous septa that connect the distal phalanx with the volar skin, creating loculi. The infection easily can invade several of these loculi. To ensure that all pockets of infection are drained, deepen the skin incision transversely across the pulp of the finger, remaining on the volar aspect of the terminal phalanx, until the skin of the opposite side of the finger is reached. Do not penetrate this skin (see Fig. 5-74). Now, bring the scalpel blade distally, detaching the origins of the fibrous septa from the bone. Proximally, take care not to extend the dissection beyond a point 1 cm distal to the distal interphalangeal crease; otherwise, the flexor tendon sheath may be damaged and infection introduced into it.
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Nerves
The digital nerves may be damaged if the skin incision drifts too far proximally. Painful neuromas can result without an appreciable area of
hyperesthesia on the finger.
Muscles and Ligaments
The fibrous flexor sheath of the profundus tendon may be incised accidentally if the incision is carried too far proximally.
Special Points
The fibrous septa that connect the distal phalanx to the skin make this an ideal site for loculation of pus. Take care to open all the loculi so that adequate drainage takes place. Unsuccessful treatment of a deep abscess may result in osteomyelitis of the distal phalanx.
How to Enlarge the Approach
The approach cannot be enlarged usefully by either local or extensile measures.
Web Space Infection
Web space infections, which involve pus in one of the four webs of the palm, are quite common. The abscess usually points dorsally, because the skin on the dorsal surface of the web is thinner than the skin on the palmar surface. Characteristically, a large amount of edema appears on the dorsum of the hand, and the two fingers of the affected web are spread farther apart than normal (Fig. 5-75).
The web spaces all communicate via the canal of the lumbrical muscles into the palm; therefore, a neglected web space infection can cause a more extensive infection by spreading up the lumbrical canal and into the palm.
Position of the Patient
Place the patient supine on the operating table, with the arm on an arm board. Use a general anesthetic or an axillary or brachial block, then raise the arm for 3 minutes before inflating an arm tourniquet (see Fig. 5-15).
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Figure 5-75 Web space infection. A large amount of edema usually appears on the dorsum of the hand, and the two fingers of the affected web space are spread farther apart than normal.
Incision
Two skin incisions are possible—longitudinal and transverse. Make a longitudinal incision in the volar skin of the palm centered over the middle of the affected web space. Alternatively, make a transverse incision following the contour of the web space about 5 mm proximal to it (Fig. 5-76).
Internervous Plane
There is no true internervous plane in this approach.
Superficial Surgical Dissection
Carefully deepen the skin incision by blunt dissection. The digital nerves and vessels lie immediately under the incision and may be damaged if the cut is too deep and a transverse incision is used. The abscess cavity usually is located just below the skin; it can be entered with very little additional dissection.
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Nerves
Both digital nerves of the web space are vulnerable with the transverse skin incision. If used make sure that an effective tourniquet, proper lighting, and fine instruments are used in the operation. As long as the skin is incised with care, the nerves should not be damaged.
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Figure 5-76 Make a longitudinal or curved transverse incision in the volar skin of the palm.
Longitudinal incisions in the web space avoid the threat to the neurovascular bundle, but scarring during the healing process may reduce significantly the ability of the two fingers of the web space to separate.
How to Enlarge the Approach
The approach cannot be extended usefully. Some surgeons recommend a second, dorsal, skin incision over the pointing area to improve drainage without appreciably increasing the morbidity of the procedure.