Rib length asymmetry in thoracic adolescent idiopathic scoliosis: is it primary or secondary?

Abstract

The development of scoliosis in animal models after inducing asymmetric rib growth suggests the possible role of asymmetric rib growth in the etiopathogenesis of adolescent idiopathic scoliosis (AIS). Asymmetric rib length is well recognized in idiopathic scoliosis; however, whether this rib asymmetry is primary or secondary has not been clearly documented. The objectives of this study were to investigate any rib length asymmetry in patients with AIS and compare those with scoliosis with syringomyelia (SS) with the intention of elucidating any relationship between rib growth and pathogenesis of AIS. Forty-eight AIS and 29 SS with apical vertebrae located between T7 and T9 were recruited. The average age was 13.5 ± 2.3 versus 12.5 ± 3.4 years, and the average Cobb angle of thoracic curve was 43.3° ± 16.4° versus 45.6° ± 22.6° in patients with AIS or SS, respectively. The length of all ribs was measured from the tip of costal head to the end of the same rib by built-in software on spiral computed tomography. At the levels of the apical vertebrae, the vertebrae above and below the apex, the mean discrepancy in rib length (concave minus convex rib) was 7, 4 and 7 mm, respectively, in AIS group (p < 0.01), and 6, 5 and 7 mm in SS group, respectively (p < 0.01). The rib length discrepancy between concave and convex sides was significantly correlated with the magnitude of the Cobb angle of thoracic curve in both AIS and SS groups (p < 0.01). Similar findings of the asymmetry of rib length in both AIS and SS patients pointed strongly to the fact that the rib length asymmetry in apical region is most likely secondary to the scoliosis deformity rather than playing a primary role in the etiopathogenesis.

Patterns of Rib Growth in the Human Child

“…Two studies have looked at the differences of left and right rib length in spine deformity patients. Zhu et al [3] analyzed patients with adolescent idiopathic scoliosis and syringomyelia, with the length of selected ribs measured from spiral computed tomography (CT) scans. They noted a difference of 4e7 mm in rib length compared with ribs above and below the apex, which also correlated to the Cobb angle of the thoracic curve.…”

“…Most studies have described abnormalities of rib or thorax growth and asymmetry in children with scoliosis [1][2][3][4][5]. Rib deformities created in experimental animals have demonstrated that abnormal thoracic development is a common feature of scoliosis [6,7].…”

The Impact of Spinal Deformity on Gait in Subjects with Idiopathic Scoliosis

“…Further studies are necessary to form physiotherapeutic programs to prevent increasing compensations and other secondary deformations such as ribs asymmetry (Zhu et al, 2011) or the temporomandibular joints dysfunctions (Smieciuch, 2011). Another goal is to concentrate on the improvement of gait pattern in persons with idiopathic scoliosis as long as the modern physiotherapy has appropriate means to facilitate gait in patients with different pathology (Adler et al, 2008) including scoliosis.…”

Body mass index in relation to truncal asymmetry of healthy adolescents, a physiopathogenetic concept in common with idiopathic scoliosis: summary of an electronic focus group debate of the IBSE

“…• in the trunk - breasts [32,33], ribs [34-39], chest wall blood supply [40,41], and iliac height [42,43];…”