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Daisuke Sakai, Masato Tanaka, Jun Takahashi, Yuki Taniguchi, Jordy Schol, Akihiko Hiyama, Haruo Misawa, Shugo Kuraishi, Hiroki Oba, Yoshitaka Matsubayashi, So Kato, Ryo Sugawara, Masato Sato, Masahiko Watanabe, and Katsushi Takeshita


For instrumented correction surgery for adolescent idiopathic scoliosis (AIS), surgeons are increasingly switching from titanium (Ti) alloy rods to stiffer cobalt-chromium (CoCr) rods. The authors conducted the first multicenter randomized controlled clinical trial to investigate whether these materials affect the outcomes in terms of spine correction and quality of life (QOL). This trial was registered at UMIN Clinical Trials Registry on September 3, 2012, under the identifier UMIN000008838 (level of evidence 1).


Female AIS patients (Lenke types 1–3, patient age 10–19 years) were recruited at 5 Japanese institutions and randomized into two cohorts: 6.0-mm-diameter Ti rods were placed in one group, and 6.0-mm-diameter CoCr rods were placed in the other. Patients were followed up at 2 weeks and 3, 6, and 12 months with radiographic examination to quantify the sagittal and coronal correction (Cobb angle, thoracic kyphosis, rib hump, and apical vertebral rotation). Patients completed questionnaires (Scoliosis Research Society–22r, 12-Item Short-Form Health Survey, and Scoliosis Japanese Questionnaire–27) at 6 and 12 months to assess QOL.


A total of 69 AIS patients were randomized to the demographically similar Ti (n = 37) or CoCr (n = 32) cohort. Four adverse events were recorded, two in each cohort, but these were not related to the rod material. At the final follow-up, both Ti and CoCr cohorts showed significant improvement in spinal correction, including the Cobb angle, thoracic kyphosis, and rib hump size. The correction rates were 68.4% and 67.1% for the Ti and CoCr cohorts, respectively. No parameters differed significantly between the cohorts at any time. Survey data showed improved but similar outcomes in both cohorts.


Both treatments (Ti and CoCr) produced similar results and were efficient in engendering clinically significant spine corrections.

Clinical trial registration no.: UMIN000008838 (UMIN Clinical Trials Registry)