Two, three, or four intercostal nerves with their vasoconstrictive sympathetic fibers were resected on the right side of 15 growing rabbits. Animals submitted to sham operations and intact animals formed two control groups. A scintigraphic study with 99mTc-methylene diphosphonate, performed on the test group 2 months after the resection, showed a significantly greater uptake of the isotope on the right than on the left costochondral junctions (p less than 0.05). Three months later the difference was still larger. There was no such significant difference in the rabbits of the two reference groups. In the rabbits of both these groups, the right and left ribs of each pair were almost equal in length. Of the denervated ribs of the rabbits composing the test group, the right ribs increased in length to a greater extent than the corresponding left ribs. The difference was statistically significant (p less than 0.05). As a consequence of this left-right difference in length, mild thoracic scoliosis convex to the left developed 2 months after the resection. The total weight and volume of the denervated right ribs increased significantly more than those of the corresponding control left ribs (p less than 0.05), but their mineral content per unit of weight or volume showed no significant difference.

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In young, growing white New Zealand rabbits the third, fourth, and fifth intercostal nerves were resected anteriorly on the right side. Six months later the animals developed structural left convex scoliosis, with a Cobb angle ranging from 15 to 31 degrees. The vascular structure changes of the anterior chest wall were evaluated by measuring surface temperature and fluorescein intensity of the pectoral muscles, and the capillary density of the pectoral and intercostal muscle and periosteal parts of the ribs after angiography. In five normal control rabbits there was neither scoliotic deformity nor significant differences in the examined vascular variables between the right and left sides. In the animals undergoing resection, the temperature of the pectoral muscle on the side of the denervation--the right side--was significantly increased (p less than 0.05), but the difference was not correlated to the degree of scoliosis. The fluorescence index was significantly greater (p less than 0.05) on the right than on the left side, this difference being fairly strongly correlated to the degree of scoliosis. The capillary densities of the costal periosteum and the intercostal and the pectoral muscle were significantly greater (p less than 0.05) on the right than on the left side, and the difference was positively correlated to the degree of scoliosis. The volume density of the periosteum of the ribs was likewise significantly greater on the right. These results demonstrate that unilateral resection of the intercostal nerves significantly increases the vascularity of the structures on the denervated side of the thorax.(ABSTRACT TRUNCATED AT 250 WORDS)