Web Space Infection
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.
Dang
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.
Anatomy of the Web Space of the
Fingers
There are three webs between the four fingers. The spaces are surprisingly long (about 2 cm) extending from the edge of the skin to the metacarpophalangeal joints. They contain both the superficial and the deep transverse ligaments of the palm, the digital nerves and vessels, and the tendons of the interossei and lumbricals. Between these various structures lies loose, fibrous, fatty tissue, tissue that can be displaced easily by infection and the formation of abscesses (Fig. 5-77; see Fig. 5-40).
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Figure 5-77 Anatomy of the web space. The neurovascular bundle runs deep to or dorsal to the superficial transverse ligament (natatory ligament) and palmar to the deep transverse metacarpal ligament. The lumbrical muscle runs along with the neurovascular bundle palmar to the deep transverse ligament, whereas the interossei pass dorsal to the deep transverse metacarpal ligament.
The important structures in the web space are listed below:
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Superficial transverse ligament of the palm (natatory ligament). This ligament lies immediately beneath the palmar skin and supports the free margins of the webs. The ligament runs superficial (palmar) to the digital nerves and vessels, and attaches to the palmar aponeurosis.
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Digital nerves and vessels. These structures lie immediately deep to the superficial transverse ligament of the palm, with the nerves on the palmar side of the arteries.
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Tendons of the lumbricals. These muscles arise from the four tendons of the flexor digitorum profundus muscle in the middle of the palm. Each lumbrical tendon passes along the radial side of its metacarpophalangeal joint before inserting into the extensor expansion on the dorsum of the proximal phalanx. Infection in the web space can spread proximally along the lumbrical tendon and enter the palm (see Fig. 5-79).
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Deep transverse ligament of the palm. This strong ligament connects the volar plates (palmar ligaments) of the metacarpophalangeal joints. It is 3 to 4 cm proximal to the superficial transverse ligaments. The lumbrical tendons are volar or palmar to it, as is the neurovascular bundle (see Fig. 5-77).
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Interosseous tendons. These muscles, which arise from the metacarpals, insert into the dorsal expansion over the proximal phalanges. Their tendons pass dorsal to the deep transverse ligament, in contrast to the lumbrical tendons, which pass on the ligament’s volar side (see Fig. 5-77).
Anatomy of the Web Space of the Thumb
The thumb is far more mobile than are any of the fingers. Its increased mobility is reflected in the unique anatomy of its web space: Both the superficial and the deep transverse ligaments are absent and the bulk of the web is filled with two muscles, the transverse head of the adductor pollicis and the first dorsal interosseous (see Figs. 5-40 to 5-42).
Adductor Pollicis Muscle
See the section regarding the anatomy of the palm.
First Dorsal Interosseous Muscle
The dorsal interosseous muscle is the largest of all the interossei. It arises from the adjacent borders of the first and second metacarpals, runs deep (dorsal) to the adductor pollicis, and inserts into the fibrous extensor expansion on the dorsum of the index finger. The muscle bulk provides most of the substance of the thumb’s web space; wasting is easy to detect clinically by gently pinching the web while the patient pinch grips. The pinch also forms the basis for one test of an ulnar nerve lesion, because the muscle is supplied by the ulnar nerve (see Fig. 5-11).
Arteries
Two branches of the radial artery, the radialis indicis and the princeps pollicis, emerge from between the two muscles of the thumb web. The radialis indicis artery runs to the radial border of the index finger, and the princeps pollicis goes to the thumb, where it divides into two palmar digital arteries. Approaches made in the center of the web space avoid damage to either artery (see Fig. 5-42).