Bio-Medical Materials and Engineering 20 (2010) 251–259 251 DOI 10.3233/BME-2010-0639 IOS Press Finite element analysis of the scoliotic spine under different loading conditions Fang-Hsin Cheng a,b , Shih-Liang Shih c , Wen-Kai Chou d , Chien-Lin Liu e , Wen-Hsu Sung a and Chen-Sheng Chen a,∗ a Department of Physical Therapy and Assistive Technology, National Yang Ming University, Taipei, Taiwan b Department of Physical Medicine and Rehabilitation, Taipei-Veterans General Hospital, Taipei, Taiwan c Department of Orthopaedic Surgery, Taipei-City Hospital, Taipei, Taiwan d Institute of Biomedical Engineering, National Taiwan University, Taipei, Taiwan e Department of Orthopaedic Surgery, Taipei-Veteran General Hospital, Taipei, Taiwan Received 24 December 2009 Accepted 1 April 2010 Abstract. The role of the vertebral body’s rotation and the loading conditions of the brace has not been clearly identified in adolescent idiopathic scoliosis. This study aimed to implement a finite element (FE) model of C-type scoliotic spines to investigate the influence of different loading conditions on variations of Cobb’s angle and the vertebral rotation. The scoliotic FE model was constructed from C7 to L5, and its geometry was the right thoracic type (37.4 ◦ ) with an apex over T7. Three loading conditions included a medial–lateral (ML) and anteroposterior (AP) force with a magnitudes of 100–0, 80–20 and 60–40 N. Those forces were respectively applied over the 6th, 7th and 8th ribs. According to an analysis of Cobb’s angle, the 100 N ML force that was applied over the 8th rib could achieve the best correction effect. Furthermore, the ML force was dominant in alterations of Cobb’s angle, whereas the AP force was dominant in alterations of the axial vertebral rotation. Additionally, the level below the apex was the most appropriate level to apply the force to correct C-type scoliosis. Keywords: Scoliosis, loading condition, Cobb’s angle, finite element analysis 1. Introduction Scoliosis is a deformity that occurs in the spine and spreads out to the torso. So far, the researches associated with scoliosis mostly focused on coronal deformation; however, it is a three-dimensional deformation, which includes vertebral body rotation in the transverse plane and the apparent rib hump. Thus, little is known about the correction effect that is due to the vertebral body’s rotation. Bracing, either rigid or flexible, is a common way to correct scoliosis. The Boston brace is a well- known rigid brace; it corrects a scoliotic spine by using pads inside of the brace to push the patient’s convex side towards the midline [1]. SpineCor [2], which is a flexible brace, was created to solve not * Address for correspondence: Chen-Sheng Chen, PhD, Department of Physical Therapy and Assistive Technology, National Yang Ming University, 155, Sec. 2, Li-Nung St., Taipei, Taiwan. E-mail: cschen@ym.edu.tw. 0959-2989/10/$27.50  2010 – IOS Press and the authors. All rights reserved