Updated: Feb 17, 2022
  • Author: E Gene Deune, MD, MBA; Chief Editor: Harris Gellman, MD  more...
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Practice Essentials

Syndactyly is the most common congenital malformation of the limbs, with an incidence of 1 in 2000-3000 live births. [1, 2, 3]  It is a failure of differentiation in which the fingers fail to separate into individual appendages. This separation usually occurs during the sixth and eighth weeks of embryologic development. The term syndactyly is derived from the Greek prefix syn- ("with, together") and the Greek noun daktylos ("finger, digit").

Syndactyly can be an isolated finding, or it can be found in association with other abnormalities (eg, polydactyly, cleft hands, ring constrictions, and craniofacial syndromes). [4]  It is a shared feature of more than 28 syndromes, including PolandApert, and Holt-Oram syndromes.

Classification is based on the severity of the clinical presentation (see Classification). Syndactyly can be classified as simple when it involves soft tissues only and as complex when it involves the bone or nail of adjacent fingers. 

Unreleased syndactyly can significantly impair finger and hand function. The impairment is worse when the syndactyly is complete, is complex, or involves the border digits with fingers of uneven lengths, such as the ring and small fingers or the thumb and index finger (see the images below).

Complete simple syndactyly of ring and small finge Complete simple syndactyly of ring and small fingers. Note ring finger proximal interphalangeal (PIP) joint flexion deformity due to complete syndactyly between border digits.
Complete simple ring and small finger syndactyly. Complete simple ring and small finger syndactyly. Note ulnar deviation of ring finger due to syndactyly of small finger.

In itself, a minor incomplete syndactyly is not an indication for surgery if the only issue is its incongruous appearance. However, a syndactyly that prevents full range of motion in the involved fingers warrants surgical release to increase functionality of the fingers. [5] Most patients with syndactyly benefit from surgical release. The timing of surgery is variable; however, if more fingers are involved and the syndactyly is more complex, release should be performed earlier. 



Several genetic abnormalities have been associated with syndactyly. [6, 7, 8]  Approximately 10-40% of cases are familial with variable penetrance. Syndactyly may occur as part of a syndrome or as sporadic events that are nonhereditary and nonsyndromic. One report indicated that there is an association between syndactyly and smoking during pregnancy. [9]



Syndactyly is the most common congenital abnormality of the hand, with a rate of 1 per 2000-3000 births. [10, 11, 12, 13] The male-to-female ratio is 2:1.



Despite appearing relatively straightforward, syndactyly release is a complex operation requiring well-honed skills. If the procedure is properly performed, the rate of complications is low, and the results are extremely gratifying for the parents and beneficial to the patients in improving hand functionality and in providing normal-appearing hands and fingers.