The incidence in Caucasians is reported as 1 in 1,339 live births, compared with 1 in 143 live births in Africans and African Americans. Ulnar polydactyly is also often part of a syndrome. In patients with African ancestry ulnar polydactyly mostly occurs isolated, whereas the presentation in Caucasians is often associated with a syndrome, though in a retrospective review, only 4 of 37 cases of ulnar polydactyly in Caucasians were syndromic. Radial or preaxial polydactyly
This is a less common situation, in which the affectation is on the side of the hand towards the thumb. Radial polydactyly refers to the presence of an extra digit (or extra digits) on the radial side of the hand. It is most frequent in Indian populations and it is the second most common congenital hand disorder. The incidence of radial polydactyly is reported as 1 in every 3,000 live births. The clinical features of radial polydactyly will depend upon the extent of duplication. Radial polydactyly varies from a barely visible radial skin tag to complete duplication. Thumb polydactyly varies from barely visible broadening of the distal phalanx to full duplication of the thumb including the first metacarpal. Radial polydactyly is frequently associated with several syndromes. Central polydactyly
This is a very rare situation, in which the extra digit is on the ring, middle or index finger. Of these fingers, the index finger is most often affected, whereas the ring finger is rarely affected. This type of polydactyly can be associated with syndactyly, cleft hand and several syndromes.
Bilhaut-Cloquet procedure
This type of procedure is recommended for Wassel types 1 and 2 (in which both thumbs are severely hypoplastic) by some congenital hand surgeons. The technique contains a composite wedge resection of the central bone and soft-tissue. This will be achieved with approach of the lateral tissue of each thumb. The goal is to achieve a normal thumb, what concerns the size, which is possible. If the width of the nail bed is greater than 70% of the contralateral thumb, it may be split. Ablation with collateral ligament reconstruction
This type of procedure is used for all Wassel types of polydactyly and is the most commonly used technique. It is recommended in all cases of thumb duplication with a hypoplastic, less-functional thumb. Otherwise, one could consider the Bilhaut-Cloquet. The ulnar thumb is preferably preserved as it is the more developed one in most cases.By detaching the radial collateral ligament from distal to proximal, a periosteal sleeve can be preserved. In this way, the radial collateral band of the radial digit, will function as the absent radial collateral ligament of the preserved ulnar thumb. Elevation of the APB and FPB is performed in Wassel type 4 duplication; this can be accomplished via the periosteum or separately. As the tendons insert proximally, the elevation is performed proximally too to potentially rebalance the ulnar thumb. After the radial thumb is amputated, the ulnar elements are centralized and fixed with a Kirschner wire.