How To Treat Polysyndactyly And Syndactyly Of The Foot

Author(s): 
Edwin Harris, DPM, FACFAS

A Guide To Anatomical Distribution And Classification

We can further group syndactyly, polydactyly and polysyndactyly according to the anatomical distribution in the extremity. Previously, the terms preaxial, central and postaxial described abnormalities involving the first ray, the central rays and the lateral ray respectively.

   A number of years ago, the hand literature began to abandon this classification in favor of using the terms radial, central and ulnar polydactyly, syndactyly and polysyndactyly. The foot and ankle literature is slowly adopting this classification by using tibial and fibular terminology to replace the older terms preaxial and postaxial. The term central remains the same. The foot and ankle literature is somewhat slow in accepting this terminology and many recently written articles continue to use the older terms.

   Mirror polydactyly of the foot is a very rare condition and is characterized by a single identifiable large metatarsal and hallux with a number of rays medial and lateral to it.10-15 This condition usually accompanies multiple visceral and skeletal anomalies including various forms of tibial agenesis and fibular dimelia. Rarely, it may occur in isolation.16

   There are a number of anatomical classifications for polydactyly and syndactyly in the foot. Most of these are adapted from hand classifications. Some of the proposed forms in these classifications have probably been added for completeness and may not actually exist. This is particularly true for fibular polydactyly and polysyndactyly. On the other hand, some clinical patterns are so unusual and bizarre that they defy all of the currently available classifications.

   Classifications are useful for communicating the nature of the deformity among professionals but in the final analysis, classifications are only descriptive and decision making occurs on a case-by-case basis as one studies the anatomy of the deformity and assesses the functional needs of the patient. It is beyond the scope of this article to discuss all of the classifications and I refer the reader to the literature.6,17-22

What You Should Know About Related Syndromes

Syndactyly, polydactyly and polysyndactyly may occur in isolation, or they may be components of an extremely large group of syndromes. The list is quite long and includes such syndromes as Bardet-Biedl syndrome, Peters syndrome, trisomy 18 syndrome, Ellis-Van Creveld syndrome, Rubinstein-Taybi syndrome, caudal regression syndrome and so many others that are beyond the scope of this article to list or discuss. It is important for the surgeon to examine each of these patients carefully for an association of these digital deformities with cranial, cardiac, renal, urogenital and neuroanatomical abnormalities and other neurological issues. Do not presume that these are isolated deformities. In many patients, these associated and more serious conditions have not yet been diagnosed.

   Tibial polydactyly. These include duplication of the hallux with and without metatarsal involvement. Metatarsal involvement may be incomplete with abnormality of the metatarsal head, wide or short shaft, or may involve incomplete or complete duplication of the metatarsal. In some cases, the medial metatarsal vestige may be incomplete and tarsal support may be tenuous. In other cases, a metatarsal vestige may simply be a fibrous remnant along the medial side of the first metatarsal and will not be visible on radiograph. The course and insertion of the abductor hallucis is usually abnormal.23

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