Syndactyly

Carl R. Wagreich

Renato J. Giorgini

Tara L. Giorgini

Syndactyly is defined as a congenital or acquired deformity in which webbing persists between adjacent digits from birth or secondary to injury (1,2). Drinkwater provided one of the earliest reports of syndactyly with symphalangism in 1917 and traced the deformity to the time of King Henry VI of England. The first member of the family who was known to have the condition was killed in 1453. His tomb was opened in 1874, and his finger bones were shown to have the same bony ankylosis as those of his descendants (3).

ETIOLOGY

Syndactyly of the toes is one of the most frequently encountered congenital anomalies (4). It often involves the second and third toes in the foot (5,6). Investigators generally agree that syndactyly is caused by a rapid arrest of embryologic development from the 6th to 8th week of intrauterine life. Because the webbing between the second and third toes is the last to disappear, this area is the most sensitive to intrauterine insult (1,7,8 and 9). Genetic factors have most often been implicated as the source for this condition (10). Traumatic causes are usually secondary to burns. Syndactyly is ten times more common in whites than in blacks and presents in roughly equal numbers in bilateral and unilateral forms. Males and females are similarly affected, although Davis and German (6) noted a greater male predominance of 68%. The incidence is about 1 in 2,500 to 3,000 live births (5,6).

CLASSIFICATION

Two classification systems for syndactyly are recognized. Davis and German (6) divided the condition into four classes, as follows:

Incomplete: Webbing does not extend to the most distal aspect of the involved digits.
Complete: Webbing extends to the ends of the involved digits.
Simple: A soft tissue connection alone exists.
Complicated: The phalanges are abnormal in size, shape, number, or arrangement.

DeValentine noted that the complicated forms may share neurovascular, tendinous, or osseous structures. Furthermore, he noted that a fifth class, complicated/complex, was used by some investigators. This class consists of three or more digits with interposed incomplete structures (7).

Temtamy and McKusick (10) described a classification based on associated syndromes and deformities. Two classes were described: syndactyly and syndromatic syndactyly. Isolated syndactyly is divided into five phenotypic types that are all inherited as autosomal dominant disorders. They are as follows:

Type 1. Zygodactyly. Webbing is usually present between the third and fourth fingers. In the foot, it usually involves the second and third toes. Syndactyly may be partial or complete. These investigators also noted that frequently one could see some degree of webbing between the second and third toes, but this was not necessarily related to type 1.
Type 2. Synpolydactyly. Syndactyly of the third and fourth fingers is present, with polydactyly of components of the fourth finger in the web. In the foot, one would see polydactyly of the fifth toe included in the web between the fourth and fifth digits.
Type 3. Ring finger—small finger syndactyly. This type manifests with complete syndactyly between the fourth and fifth fingers, typically bilaterally. The feet are not affected.
Type 4. Hass type. This type involves complete syndactyly of all fingers. Occasionally, patients have a sixth metatarsal and phalanx. No foot involvement occurs.
Type 5. Syndactyly with metacarpal and metatarsal fusion. There is syndactyly of the third and fourth fingers and the second and third toes. Associated findings are fusion of the fourth and fifth metacarpals and metatarsals and occasionally the third and fourth metatarsals.

Syndromatic syndactyly is divided into two groups: the first comprises syndromes in which syndactyly is predominant, and in the second group, syndactyly is secondary to other medical problems. The list of associated syndromes and deformities is voluminous. A partial list includes split hand-split foot (Czeizel-Losonci syndrome) (11), talipes equinovarus (12), tibial hypoplasia or aplasia, polydactyly (13), occipitocervical encephalocele, vertebral fusion (14), cleft palate, Apert syndrome (15), renal and anogenital malformations (16), mental retardation (17), dysplasia epiphysealis hemimelica (18), cardiac conduction deficits (19), amniotic band syndrome (20), and Fraser syndrome (cryptophthalmos, hidden eye syndrome) (21).

SURGICAL TREATMENT

The definitive treatment of syndactyly is surgery. Virtually all reports in the literature represent syndactyly as a purely cosmetic problem, yet the emotional sequelae of the deformity are recognized (8,22). Some authors believe that because the problem is purely cosmetic, it should not be repaired surgically (23,24). However, some reports have noted syndactyly involving the hallux and second digit that resulted in the use of altered gait patterns to avoid pain (2).

Surgery is generally performed in the pediatric patient after 1 year of age because the results in younger children are generally poor. At this earlier age, the commissures tend to close and advance. Children older than 5 years of age are subject to ridicule in school. Therefore, investigators have recommended that surgical correction be performed when patients are between the ages of 2 and 4 years (5). DeValentine recommended waiting until adolescence so the child could participate in the decision and better assist in the postoperative care. However, he also indicated that more complex cases could require earlier intervention, generally between the ages of 1 and 5 years. Preference was expressed for the upper limit of this range, so a more complete radiographic assessment and better intraoperative visualization of anatomic structures could be available (7).

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