Fig. 174.—Splint used after Operation for Dupuytren's Contraction.
Supernumerary Fingers (Polydactylism).—These may coexist with supernumerary toes, and the condition is often met with in several members of the same family. Sometimes the extra finger is represented by a mere skin appendage, the nature of which may only be indicated by the presence of a rudimentary nail; sometimes it contains bone representing one or more phalanges, or it may be fully formed ([Fig. 175]). In the majority of cases the superfluous finger should be removed.
Fig. 175.—Supernumerary Thumb.
(Photograph lent by Sir George T. Beatson.)
Congenital Deficiencies in the Number of Fingers.—One or more fingers may be absent, such deficiency being often associated with imperfect development of the radius or ulna; or they may be represented by short rounded stumps, which are ascribed to the strangulation of the digits by amniotic bands in utero—the so-called intra-uterine amputation.
Webbing of Fingers (Syndactylism).—Congenital webbing or fusion of the fingers may be associated with polydactylism or with congenital hypertrophy, and, like other digital deformities, may affect several members of the same family. The degree of fusion ranges from a web of skin joining the fingers to a fusion of the bones, the latter being well seen in skiagrams. If an operation is decided upon, it should not be performed until the age of five or six years. In the simplest cases it is only necessary to divide the web and to unite the cut edges of skin along each finger by sutures, a skin graft being inserted into the angle between the fingers. An operation in which the skin is dissected up in the form of flaps may be required, but it should not be lightly entered upon, as in young children it has been known to be followed by gangrene of one or more of the digits.
Congenital Hypertrophy of the Fingers.—This is a form of local giantism affecting one or more digits, and involving all the tissues. The finger is usually of abnormal size at birth, and continues to grow more rapidly than the others, and it may also come to deviate from its normal axis. Such a finger should be trimmed down or removed, to permit of the use of the other digits.
Trigger Finger ([Fig. 176]).—This is an acquired condition in which movement of a finger or thumb, either in flexion or extension, is arrested, and is only completed with the assistance of the other hand. The obstacle to movement is usually overcome with a jerk or snap suggesting a resemblance to the trigger of a gun or the blade of a clasp-knife. The commonest cause is a disproportion between the size of the tendon and its sheath, such as may result from a localised thickening of the tendon. Recovery usually takes place under massage and passive movements. Failing this, the thickened portion of the tendon is pared down to its normal size; if it is the sheath of the tendon that is narrow, it is laid freely open.