How To Treat Polysyndactyly And Syndactyly Of The Foot

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Edwin Harris, DPM, FACFAS

   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

   Central polydactyly. This is the least common form of polydactyly. It accounts for 3 to 6 percent of cases.24 In most cases, there is complete duplication of one or more central rays. One can identify a complete metatarsal with its phalanges and its relationships to the tarsal structures can be variable. It may share an articulation with another ray on a single cuneiform or may have a separate accessory cuneiform. On occasion, one can identify an extra metatarsal but the phalangeal structures fail to differentiate.25 The literature has also reported bifid distal metatarsal variations.26

   Fibular polydactyly. Anomalies on the lateral side of the foot are much more common than those on the medial side. They are characterized by more or less complete duplication of the phalanges. The metatarsal head may be slightly widened, bifid, dumbbell-shaped, V-shaped, Y-shaped, T-shaped or the metatarsal may be completely duplicated. Generally speaking, the lateral component has a higher incidence of intrinsic anomaly that is likely to make it the least desirable to attempt to salvage. On rare occasions, the lateral metatarsophalangeal joint fails to form. However, there are many exceptions to this rule.27

   Tibial syndactyly. Rarely, the first and second digits may be syndactylized. When this occurs, there is usually a normal row of phalanges in both the first and second toes. The metatarsophalangeal joints are normal.

   Central syndactyly. The most common form of central syndactyly is more or less complete syndactyly of the second and third toes. The middle phalanx of the third toe is likely to be anomalous and may not have a physis. The middle phalanx of the second toe is often wedged with the apex lateral so the distal portion of the second toe abducts. Due to these abnormalities, progressive deformity of the two toes is more likely to occur with subsequent growth than in more lateral forms of this condition. Less frequently, the third and fourth toes are involved. Very rarely, the fourth and fifth toes are involved.

   Critical features in this form of syndactyly are the extent of the fusion of the skin envelope and the presence or absence of phalangeal fusion. Of interest, when there is fusion of the phalanges themselves, this deformity is frequently associated with macrodactyly of one or both of the involved toes.

   Fibular syndactyly. In this deformity, a single skin envelope contains the fourth and fifth toes. Most frequently, the phalanges of each of the pair are separate and distinct. It is possible that the fifth toe could be a biphalangeal toe instead of having three distinct phalanges.

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