[Congenital hand malformation--local disturbance in the limb bud and longitudinal deficiency: an experimental study...

Experimental congenital malformation produced in fetal chickens to investigate any correlation between a local disturbance in the limb buds and longitudinal deficiency, and to elucidate the pathogenesis of radial and ulnar ray deficiencies. Fertilized White Leghorn eggs were incubated at 38.0 degrees C and windowed. The right wing bud of the embryos was locally cauterized using a bipolar microcoagulator under a microscope. Cauterization was carried out from 2.5 days to 5.5 days of development, at 12-hour intervals. Each wing bud was divided into 6 areas: axial (distal and proximal), preaxial (distal and proximal) and postaxial (distal and proximal). After cauterization the eggs were sealed with micropore tape and further incubated until the 21st-23rd day. The chick wings were then removed and investigated macroscopically and roentgenographically. The wing buds had been examined microscopically after cauterization on the 3rd day until ray deficiencies were produced on the 5th day. Radial ray deficiencies were produced by cauterization in the distal preaxial area, and ulnar ray deficiencies by cauterization in the distal postaxial area. These results indicated a peculiarity of the longitudinal axis. However, the critical periods of the radial and the ulnar ray deficiencies were the same; from immediately after the formation of the wing bud to before the formation of the digital plate. The patterns of the combined defects in the digits and of other associated deformities were quite similar to those found in human malformations. Microscopically necrosis in the mesoderm and in the overlying ectoderm of the pre and postaxial areas of the tip of a wing bud caused defects in the cartilaginous primordium in the same ray.