J Korean Orthop Assoc.  2018 Dec;53(6):530-539. 10.4055/jkoa.2018.53.6.530.

Analysis of Congenital Postaxial Polydactyly of the Foot Using Magnetic Resonance Imagings

• Woo SH
• Baek HS
• Kim YK
• Choi JY

• KMID: 2430060
• DOI: http://doi.org/10.4055/jkoa.2018.53.6.530

Abstract

PURPOSE
We aimed to evaluate the magnetic resonance imaging (MRI) findings of congenital postaxial polydactyly of the foot.
MATERIALS AND METHODS
Three-hundred and forty-seven feet of 288 patients who underwent congenital postaxial polydactyly or polysyndactyly correction were divided into five subtypes according to the radiographic shapes of deformity origins (widened metatarsal head, bifid, fused duplicated, incompletely duplicated, or completely duplicated). MRIs were assessed to determine whether they unrevealed areas were fused or separated. MRI was also used to assess cases with radiographic phalangeal aplasia.
RESULTS
Huge variations were noted in MRIs. Fusion or separation at the base or head between original and extra digits were observed, and MRI effectively depicted phalangeal aplastic areas.
CONCLUSION
MRI evaluations of congenital postaxial polydactyly of the foot are useful for determining the anatomical statuses which were not visualized by plain radiography (level of evidence: 3).

Keyword

postaxial polydactyly; polysyndactyly; magnetic resonance imaging

MeSH Terms

Congenital Abnormalities
Foot*
Head
Humans
Magnetic Resonance Imaging
Metatarsal Bones
Polydactyly*
Radiography
Syndactyly

Figure

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  Figure 1 Four zones of radiographic deformity from proximal to distal.

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  Figure 2 Five different deformity types. (A) The angle between two separate articular surfaces (a angle) was measured for the widened metatarsal head type. Bifid type was defined as sharing area of more than 50% of entire metatarsal length (B), and the fused duplicated type was defined as sharing less than 50% (C). Hypoplasia was used to differentiate the incompletely (D) and completely (E) duplicated types.

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  Figure 3 Two different patients showed similar radiographic findings of widened metatarsal head type polydactyly (A, C). However, magnetic resonance imagings revealed separation of the metatarsal head in one (B) and fusion in the other (D).

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  Figure 4 Radiograph of an 18-month-old male patient showing non-visualization of the middle phalanx (A), whereas magnetic resonance imagings (MRIs) showed two distinctly separate middle phalanges (B). Radiograph of an 11-month-old female patient showing one middle phalanx (C), whereas MRIs showed two with proximal fusion (D).

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  Figure 5 Aplasia of the distal phalanx was suspected based on radiographic findings (A), whereas magnetic resonance imaging showed incompletely duplicated type polydactyly of the distal phalanx (B).

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  Figure 6 Radiographs of two patients (A, C) showed similar complex type polydactylies (incomplete duplication at the metatarsal level and fused duplication at the proximal phalanx). However, magnetic resonance imaging revealed different findings at metatarsal heads (B: fusion, D: separation), while bases of proximal phalanges were fused in both patients.

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