Comparison of stainless steel and titanium alloy instruments in posterior correction and fusion surgery for adolescent idiopathic scoliosis-prospective cohort study with minimum 2-year follow-up

This prospective study compares the radiographic and clinical results of posterior correction and fusion surgery for adolescent idiopathic scoliosis (AIS) using stainless steel and titanium alloy instruments. The subjects consisted of 65 AIS patients who underwent posterior correction and fusion surgeries using a 5.5-mm-diameter rod at a single institution. Of these, 27 patients were treated using stainless steel instruments (S group) and 38 were treated using titanium alloy instruments (T group). The mean age at the time of surgery was 14.4 +/- 3.5 years. The radiographic findings, intra-operative time, estimated blood loss, perioperative complications, and SRS-22 (a patient questionnaire used in the clinical evaluation of idiopathic scoliosis outcomes) were examined. The mean preoperative Cobb angle of the major curve was 62.5 +/- 17.2 degrees in the S group and 57.8 +/- 13.2 degrees in the T group (p = 0.407). Postoperatively, the curves were corrected to 11.2 +/- 10.5 degrees and 10.3 +/- 8.5 degrees (p = 0.384), with mean correction rates of 83.4 +/- 12.2% and 83.1 +/- 11.6% (p = 0.940), respectively. At the final follow-up, although the mean correction loss was slightly larger in the S group (4.4 +/- 5.2 degrees) compared with that in the T group (2.3 +/- 5.5 degrees), the values were not significantly different (p = 0.118). The coronal balance and sagittal balance were also not significantly different between the two groups at the final follow-up. The function, pain, and mental health sub-scores and the total score for SRS-22 show a tendency for better outcomes in the T group; however, there were no significant differences between the two groups. Thus, there was no statistical difference in radiographical and clinical outcomes between AIS patients treated surgically using stainless steel instruments and those treated using titanium alloy instruments.