Correlation of rib length asymmetry and rib hump deformity in patients with thoracic scoliosis secondary to Chiari malformation

English Keywords:Chiari malformation  Scoliosis  Rib length  Asymmetry  Rib hump

English Abstract:

  【Abstract】 Objectives: To evaluate the rib length asymmetry in patients with thoracic scoliosis secondary to Chiari malformation and to correlate it to rib hump(RH) deformity, so as to elucidate whether the rib length asymmetry is primary or secondary. Methods: There were 38 patients in the group of scoliosis secondary to Chiari malformation(SSCM, group A) with a mean Cobb angle of 44.9°±23.5°(range, 26°－108°), a mean age of 12.3±3.6 years(range, 9-17yrs), a mean height of 155.4±10.8cm and the apical vertebrae ranging from T7 to T9. There were 58 patients in AIS group(group B) with a mean Cobb angle of 43.9°±17.2° (range, 28°-102°), a mean age of 13.7±2.6 years(range, 10-18yrs) and a mean height of 157.6±11.5cm. All AIS patients had a major thoracic curve, and the apical vertebrae ranged from T7 to T9. Rib hump was measured with scoliometer. 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. The rib length discrepancy was compared between concave and convex sides at apical vertebral level, end vertebral level and no scoliosis levels. The correlation of rib length discrepancy with the magnitude of the Cobb angle and RH at apical vertebral level. Results: At the levels of the apical vertebrae, the vertebrae above and below the apex, the mean rib length was significantly bigger in the concave side in both SSCM group and AIS group(P<0.01）, with no difference observed at the end vertebral level. The RH averaged at 12.7°±4.0° and 11.9°±3.5° in SSCM group and AIS group, respectively. The rib length discrepancy between concave and convex sides at apical vertebral level was significantly correlated with the magnitude of the Cobb angle and RH in both AIS and SSCM groups(Cobb angle: for AIS group, r=0.463, P=0.003; for SSCM group, r=0.562, P=0.001; RH: for AIS group, r=0.328, P=0.02; for SSCM group, r=0.373, P=0.01). Conclusions: Rib length asymmetry at the apex vertebral level is similar in both scoliotic groups, and significantly correlated with RH deformity, which points strongly to the fact that the rib length asymmetry in apical region is most likely secondary to the scoliosis deformity.