Characteristics of congenital scoliosis in a mouse model.

Pregnant mice were exposed to 600 ppm of carbon monoxide on gestation day 9. The carbon monoxide exposure produced 38 spinal anomalies in 17 offspring with congenital scoliosis. Microcomputer tomography improved the identification of spinal anomalies and detected more affected animals, as compared when magnified radiographs were used. The curves were measured and ranged from mild to moderate at an age that corresponds to childhood and, on average, remained at the range of mild to moderate through near-maturity. The group of mice with congenital anomalies near maturity contained severe curves. The bone mineral density (BMD) determined by microcomputer tomography in the mice with congenital scoliosis was the same as that in the controls. The cervical spine BMD was higher than the thoracic BMD, which was higher than the lumbar region in the controls and affected animals. The BMD was highest in the apex of the congenital curves in the animals that were near maturity. This relationship was not seen in the younger mice with congenital curves. Histology revealed growth rates in the hemivertebrae, which, over the last half of the growth period measured, had one-third less growth than the adjacent vertebrae. The hemivertebrae were wedged, but the adjacent disks were not.