Effects of intercostal nerve resection on the longitudinal rib growth in the growing rabbit

Abstract

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.

A new concept for the etiopathogenesis of the thoracospinal deformity of idiopathic scoliosis: summary of an electronic focus group debate of the IBSE

“…However, do not the results of the studies in rabbits [1] show that it is the induced sympathetic dysfunction that leads to the development of the thoracospinal deformity with the characteristics of human IS, and not vice versa? Moreover, if the altered vascularization of the hemithorax on the concave side of the curvature was secondary to the spinal deviation, should not the lateral deviation of the spine and the vertebral rotation affect the sympathetic chain on the side of the convexity rather than on the concavity?…”

A physiological approach to surgical treatment of progressive early idiopathic scoliosis

“…These changes were ascribed to disturbed sympathetic function. Indeed, in growing rabbits stimulation of the longitudinal rib growth by unilateral resection of intercostal nerves, including the sympathetic fibres, resulted in hyperaemia of the denervated anterior hemithorax [1], increased longitudinal rib growth [2] and scoliosis with the convexity to the opposite side of the denervation and characteristics of IS in humans [3].The inter-related results of these and other clinical and experimental studies have provided evidence supporting the thoracospinal theory of the pathogenesis of IS. According to this new theory, stimulation of longitudinal growth of the left ribs is the origin of right convex IS in adolescent girls [15].…”

“…These changes were ascribed to disturbed sympathetic function. Indeed, in growing rabbits stimulation of the longitudinal rib growth by unilateral resection of intercostal nerves, including the sympathetic fibres, resulted in hyperaemia of the denervated anterior hemithorax [1], increased longitudinal rib growth [2] and scoliosis with the convexity to the opposite side of the denervation and characteristics of IS in humans [3].…”

Vascular changes in the chest wall after unilateral resection of the intercostal nerves in the growing rabbit

“…This interpretation is supported by the earlier observed increase in osteogenic activity evidenced by an increase in the isotope uptake in the area of the costochondral junction (2).…”

“…In the experimental model applied in this study, the development of scoliosis was associated with overgrowth of the denervated ribs (2). As the possibility of postoperative neuromuscular deficit was ruled out by electromyography (l), it would appear that the stimulation of growth was largely a result of an increase in the vascularity and the blood flow of the denervated ribs.…”