Prognostic role of rib hump in overlying thoracic curve correction above selective fusion for lenke 5 idiopathic adolescent scoliosis

Study design: Prospective study. Objective: To assess whether rib hump is a prognostic factor of final thoracic Cobb angle. Summary of Background Data: Correction of thoracolumbar/ lumbar curve, preoperative thoracic curves angle, thoracic curves angle on bending, the thoracolumbar-lumbar angle/thoracic curves angle ratio, thoracic kyphosis, and growth stage influences spontaneous correction of uninstrumented thoracic curves angle above selective fusion for Lenke 5 Adolescent Idiopathic Scoliosis. Indeed, preoperative rib hump has never been expressly evaluated as a prognostic factor of final thoracic curves angle. Methods: In total, 50 patients with Lenke 5 Adolescent Idiopathic Scoliosis, selectively instrumented with posterior construct were included. Two patients were lost to follow-up and 48 had follow-up ≥2 years. Demographic data, preoperative thoracic rib hump (measured in millimeter in trunk anteflexion), and radiologic spinal parameters were recorded preoperatively and at last consultation. T test was used to compare mean values, linear and logistic regressions to assess predictability of final thoracic curve angle. Results: Main thoracolumbar-lumbar curve angle decreased from 47 degrees (range, 36–72 degrees) to 12 degrees at the final consultation (range, 1–28 degrees). Thoracic curves angle decreased from 26 degrees (range, 2–40 degrees) preoperatively to 16 degrees (range, 2–41 degrees) at the final consultation (P=0.001) (correction= 37%). Preoperative rib hump was present in 10 patients. Final thoracic Cobb angle was 27 degrees (8–41 degrees) in patients with rib hump and 14 degrees (0–32 degrees) in patients without rib hump (P<0.001).Multiregression highlighted thoracic curves angle on bending (P=0.001), preoperative thoracic curves angle (P=0.011) and rib hump (P=0.012) as prognostic factors of higher final thoracic curves angle. Conclusion: Rib hump significantly influenced final thoracic curves angle.