Abstract
Background
Thumb epiphyses cannot be visualized on radiographs in infants with radial polydactyly, making it difficult to classify by Wassel type. The purpose of this study was to identify radiographic features that distinguish a separate epiphysis from a shared epiphysis. This may assist in operative planning and establishing prognosis.
Methods
The charts of 34 radial polydactyly patients treated with surgical reconstruction from 2008 through 2012 were retrospectively reviewed. Measurements of the most proximal bones involved in the duplication, including length, width at shaft, width at base, distance between radial and ulnar thumb, and angle between radial and ulnar thumb, were taken from PA radiographs of the thumb by four blinded individuals. The interclass correlation coefficient was calculated to determine inter-observer reliability. Operative notes were reviewed to distinguish between shared and separate epiphyses. Several indices were created from these measurements.
Results
Radiographic measurements showed high inter-observer reliability. There were statistically significant differences between patients with separate and shared epiphyses for indices for the width shaft index, interspace distance, the angle × interspace distance, and the angle × interspace index.
Conclusion
Radiographic differences exist between children with separate and shared epiphyses. In patients with shared epiphyses, the radial thumb tends to be smaller, closer to the ulnar thumb, and less divergent. Threshold values were identified for predicting the status of the epiphysis based on the angle × interspace distance and the angle × interspace index. These values may be used to help determine in advance of surgery if a shared epiphysis exists.
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Conflict of Interest
Michael H. Johnson, MD declares that he has no conflict of interest.
Roshan T. Melvani, BLA declares that he has no conflict of interest.
Neil N. Patel, BLA declares that he has no conflict of interest.
Christine J. Cheng, MD, MPH declares that she has no conflict of interest.
Richard L. Hutchison, MD declares that he has no conflict of interest.
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All procedures followed were in accordance with the ethical standards of our Institutional Review Board and with the Helsinki Declaration of 1975, as revised in 2008.
Statement of Informed Consent
No patient identifiers being used; the IRB decided that informed consent was needed. No informed consent was obtained per IRB guidelines.
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Johnson, M.H., Melvani, R.T., Patel, N.N. et al. Radiographic indicators of a shared epiphysis in radial polydactyly. HAND 9, 329–334 (2014). https://doi.org/10.1007/s11552-013-9593-7
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DOI: https://doi.org/10.1007/s11552-013-9593-7