REIDER PART 1
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112 Chapter 4 Hand and Wrist

Figurę 4-17. Cupping the hand.

interphalangeal joints cxtcndcd while thc other fingers form the normal resting arcade (Fig. 4-19B).

The skin of the palmar surface of the hand is dra-matically different from that of the dorsum. The palmar skin is thickened, hairless, and marked with discrete creases that identify the sites of no motion. This bound down thickened skin, not only protects the underlying structures such as the nerves, arteries and tendons, but allows for stability to the skeleton for grasping and manipulating objects. Localized calluses may give clues about the persons occupation or avocations.

Figurę 4-18. Normal resting arcade of finger flexion.

The distał and proximal flexion creases of the fingers mark thc approximate locations of the DIP and the PIP joints, respectively (see Fig. 4—16). The web flexion creases at the level of the web spaces are misleading because they mark the midpoint of the proximal pha-langes. The true location of the volar aspect of the metacarpophalangeal joints is signified by the distal palmar creases.

Because the palmar skin is the common site of inter-face between human beings and the surrounding envi-ronment, it is freąuently subject to lacerations and penetrating injuries. These injuries, in turn, may lead to closed-space infections of the Fingers and hand. Localized swelling and erythema of the fingertip, for example, may reflect a felon, the common term for a closed-space infection of the fingertip (see Fig. 4-190). The presence of vesicles suggests a herpetic felon or her-petic whitlow. Fusiform swelling extending along thc middle and proximal phalanges into thc distal palm may signify a closed infection of the flexor tendon sheath (see Fig. 4-19D). This fusiform swelling is one of the four classic signs of flexor tendon sheath infection, often called the four Cardinal signs of Kanavel. The other three are that the volar surface of the involvcd finger is tender, the finger is held in a slightly flexed position at rest, and passive extension of the finger exacerbates the patienfs pain. Other closed-space infections may occur in the thenar or midpalmar spaces. These would result in localized painful swelling in the first web space or center of the palm, respectively.

Epidermal inclusion cysts, the result of old penetrating injuries, may cause nodular swellings of the fingertips or other areas of the volar surface of the fingers. A nodular swelling at the lcvel of the web flexion crease of thc fingers is most commonly due to a gangiion of the Jlexor tendon sheath (see Fig. 4-19£). These ganglia are nor-mally only a few millimeters in diameter and thus only palpable, although large ones may occasionally be visible. Ganglia hurt because they often lay under the digital nerve and act like a stone pinching the nerve between it and an object carried in the hand.

In most individuals two creases, known as the distal palmar flexion crease and the proximal palmar flexion crease, cross the hand. The morę transverse portions of these two palmar flexion creases combine to identify the level of the metacarpophalangeal joints of the fingers (transverse palmar crease).

Just deep to the palmar skin lies a layer of fascia known as thc palmar aponeurosis. In its normal State, this tissue is not dircctly visiblc. However, a yisible nod-ule in linę with the ring or little fingers may be the first sign of Dupuytrens disease (see Fig. 4-19F). This condi-tion, which is often familial and tends to occur in older men, can progress to thc formation of longitudinal fibrous bands that gradually puli the involved finger or fingers into a progressively flexed, contracted position.