Rib-vertebral angle asymmetry in idiopathic, neuromuscular and experimentally induced scoliosis

Abstract

The concave and convex rib-vertebral angle (RVA) at levels T2-T12 was measured on AP radiographs of 19 patients with right convex idiopathic thoracic scoliosis and 10 patients with major thoracic right convex neuromuscular scoliosis. The difference between the angles on the concave and the convex sides, the RVAD, was calculated. The RVAs were also measured on radiographs from three animal groups in which spinal curves had been induced experimentally in a variety of ways. Group 1 comprised 16 rabbits that had been subjected to selective electrostimulation of the latissimus dorsi, the erector spinae and the intercostal muscles. Group 2 comprised four dead rabbits whose spines had been subjected to manual bending. Group 3 comprised eight rabbits that had undergone mechanical elongation of one rib. In both the idiopathic and the neuromuscular group, the convex RVA was smaller than the concave RVA between levels T2 and T8, with a maximal difference between T4 to T5. From T9 to T12 the concave RVA was smaller than the convex. The RVA in relation to the scoliotic segment, i.e. the apex level of the curve and the two neighbouring vertebrae above and below this level, showed similar results. With increasing Cobb angle the RVADs increased linearly with the greatest difference at the second vertebra above the apex. In the three experimental groups the pattern of the RVADs between T6 to T12 was basically similar to the findings of the clinical study. From the results of these clinical and experimental studies, it is concluded that the typical pattern of the RVAs on the concave and convex sides seems to be independent of the underlying cause of the spinal curvature. It is likely that the RVADs result from a passive mechanical adaptation of the ribs to the lateral curvature of the spine.

Changes of concave and convex rib–vertebral angle, angle difference and angle ratio in patients with right thoracic adolescent idiopathic scoliosis

“…1). Our data differ from those published by Sevastik et al [4] probably due to different curve patterns.…”

“…For this reason, we decided to include patients of the same gender with similar curve patterns. Sevastik et al [4], Kristmundsdottir et al [6], Modi et al [7], Xiong et al [15], and Burwell et al [19] showed that RVADs increase linearly with a wider Cobb angle, convex apical RVA is as important as apical RVAD, and RVADs are largest at two and three vertebral levels above the apex where they correlate significantly and positively with the Cobb angle.…”

“…This line was then extended medially to intersect the vertebral line creating the RVA. The vertebral line was always drawn perpendicular to the lower border of each thoracic vertebra to minimise the bias of vertebral body wedging, particularly at and around the apex of a scoliotic curve [4,7,9,15,16].…”

“…Introduced by Mehta in 1972, the rib-vertebral angle (RVA) was originally described to differentiate between resolving and progressive infantile scoliosis and it has become a topic of interest for many researchers [4][5][6][7][8]. Subsequently, it has been used in analyses of the effects of various surgical procedures on the rib cage in patients with idiopathic scoliosis and in studies of the shape of the thorax during growth [9][10][11].…”

The effects of pineal gland transplantation on the production of spinal deformity and serum melatonin level following pinealectomy in the chicken

“…In addition, in all groups the rib-vertebra angles (RVAs) of the convex and the concave side of the scoliotic curvature were measured on radiographs from level T1 to T8 as described previously by Mehta [24] and Sevastik et al [28], and the difference between the two, the RVAD (RVA concave-RVA convex), was then calculated for differentiation between progressive and regressive scoliosis. The mean RVAD for each group was calculated, and these values were used for the analysis.…”