There are five types of ulnar polydactyly
Type I: small cutaneous appendage in the form of a wartlike skin nubbin that is raised above the skin surface without nail or bone
Type II: extraneous digit with a small nail and ossicle (bone) with or without a poorly developed joint of which the digit lacks tendons, does not articulate (no joint) with the fifth metacarpal (5th is small finger, metacarpal in the bone in the palm) , and does not have any function
Type III: more developed than type II, but the proximal (nearest the palm) phalanx (small bone in the finger) is infrequently fully develped and often hypoplastic (under developed) or absent. Despite this the middle phalanx or remaining proximal phalanx articulates with a bifid fifth metacarpal head. The proximal phalanx may be fused to the fifth metacarpal at a 90-degree angle
Type IV: is a fully developed sixth digit with its own metacarpal shaft.
Type V: is associated with syndactyly (ie polysyndactyly). Other polydactyly case that include bony anomalies such as bifurcation of the distal phalanx, angular deformities, or cross bones are grouped into this type.
The goals of treatment in ulnar polydactyly are for improving function and appearance and social acceptance. Treatment of congenital hand differences at an early age allows maximal cerebral (brain-to-hand) functioning of hand parts and should be completed before school age.
- Type I requires no treatment (unless there is an objection to the small "wart-like" skin tag).
- Type II will often require surgical excision. Only if the pedicle is very narrow can ligation be done. The practice of ligation in the newborn is sometimes condemned, especially without evaluating the patient. Ligation can be done using a 4-0 silk suture for pedunculated polydactyly, but the patient’s family should be warned about possible complications. Ligation can leave a small nubbin, sometimes with retained bone or cartilage. This can be symptomatic and require surgical excision. Gangrene of the digit that has not sloughed or infection may complicate ligation.
- Types III, IV,and V require surgical removal to improve function and appearance and to prevent complications. Type V requires sometimes more involved surgical reconstruction of the hand in addition to that of polydactyly. Surgical treatment may require skin release, balancing of tendons, alignment of joint surfaces, rearrangement of intrinsic musculature, or osteotomy to correct angular deformities. Incisions should be made in the mid-axial line and retain adequate skin for closure; otherwise with growth, a scar may migrate volarly and create a contracture. If necessary, the wound can be closed with a Z-plasty to prevent longitudinalscarring for incisions longer than 1 cm in children around 1 year old.
Ulnar Polydactyly by Ghazi M. Rayan, M.D., and Bret Frey, M.D.; Plastic & Reconstructive Surgery. 107(6):1449-1454, May 2001.
Congenital Malformations of the Hand and Forearem edited by D. Buck-Gramcko; chapter on Ulnar polydactyly; London: Churchill-Livingstone, 1998.
eMedicine article on Supranumerary Digit by Carter G Abel, MDDevelopment of the Human Hand: A Short, Up-to-Date Overview by Helga Fritsch
Hand--Wikipedi article--good pictures of normal anatomy