Purpose: Various combinations of central polydactyly, syndactyly, and cleft hand have been frequently observed in the individual hands and feet in the same patients. Little is known, however, about the early changes of abnormal induction of digital rays during limb development. To determine the early changes and process of formation of central polydactyly, syndactyly, and cleft hand, we experimentally induced these anomalies in the hind limbs of rat embryos and discussed the relationship among these abnormalities.
Methods: Inbred WKAH/Hkm rats were used for this study. Pregnant females were treated with busulfan at embryonic day (E) 11. The embryos were removed at E12 to E21 and stained with alcian blue and alizarin red S. The abnormal changes in the treated embryos' hind limbs were observed with a microscope.
Results: The edges of the footplates were irregular, and their growth was reduced at E14. By E15, abnormal clefts in the distal edge were present that disrupted the central digits (2 to 4) of the footplates. Because of these abnormal clefts, the digital rays were bent or branched, and the neighboring interdigital spaces were narrowed. These changes led to central polydactyly, syndactyly, and central deficiencies.
Conclusions: These findings show that central polydactyly, syndactyly, and central deficiencies have the same early morphological changes: abnormal clefts in the central part of the footplate.