Comparison of surgical correction rates between titanium and cobalt-chrome-alloy as rod materials in adolescent idiopathic scoliosis

Numerous biomechanical studies comparing titanium (Ti) and cobalt-chrome-alloy (CCM) rods are described in the literature. However, there is a dearth of literature comparing the two rod materials in adolescent idiopathic scoliosis (AIS). Therefore, the purpose of this study is to compare the correction rates of Ti and CCM rods in the treatment of AIS with double major curves. We enrolled 45 patients with AIS who underwent surgery between 2009 and 2012. We divided patients into two groups, Group A (n=29) treated with six-millimeter Ti rods and Group B (n=16) treated with six-millimeter CCM rods. The rod-derotation maneuver was used for correction. We measured pre- and postoperative indices of coronal alignment (Cobb's angle, coronal balance, T1-tilt, clavicle angle) and sagittal alignment (sagittal vertical axis, thoracic kyphosis, lumbar lordosis). In our study, there were no significant differences between the two groups with respect to demographics or curve characteristics (P>0.05). In Group A, thoracic and lumbar curvature correction rates were 71.2% and 66.8% respectively, and in Group B they were 71.2% and 73.3%, respectively (P=0.664 and 0.09). There were no significant differences between the two groups in coronal or sagittal factors (P>0.05) except for greater postoperative lumbar lordosis in the CCM group (P<0.001). In conclusion, Ti and CCM rods showed similar correction rates in the sagittal and coronal planes for the surgical correction of AIS with double major curves. Biomechanical studies of Ti and CCM rods in vitro is different in biological condition.