http://congenitalhand.wustl.edu/2011/06/syndactyly.html and http://congenitalhand.wustl.edu/2011/07/frequently-asked-questions-about.html
The long and ring finger are most commonly involved in syndactyly whereas the thumb and index finger are uncommonly conjoined. There are several important points to consider regarding thumb and index finger syndactyly:
1) The syndactyly between the thumb and index finger is functionally the most significant type of syndactyly as it limits pinch and large object grasp. Without a wide, soft webspace between the thumb and index finger, function of the hand is difficult and will be frustrating to the child.
2) It is also notable as it should be correctly at a younger age to de- tether the index finger as otherwise, the index finger can deviate towards the shorter thumb with growth. While long finger and ringer syndactyly may be corrected at any age (preferences vary, but we often aim to correct at 18 months), we correct the thumb and index finger syndactyly closer to 6 months of age, if not before.
3) Finally, thumb index syndactyly is a more difficult correction as the typical techniques are not applicable. We like to use a dorsal flap to cover the web space to create a soft, function webspace.
|Thumb and index finger syndactyly. Note the large space between the index finger and the long finger (which is joined to the ring finger and is contracted).|
|Another view of both syndactylies- thumb/ index on the left and long/ ring finger in the center.|
|Here I isolate the thumb and index finger syndactyly.|
|This is an unusual correction of syndactyly as mentioned above. In this case we borrowed skin between the index and longer finger and bring it over towards the new space between the thumb and index finger (with the zig- zag separation).|