Randomized double-blinded clinical trial to evaluate the safety and efficacy of super-elastic memory alloy spinal rod versus standard titanium spinal rod in patients with adolescent idiopathic scoliosis: five-year follow-up results

Abstract

INTRODUCTION: The current trend in spinal instrumentation is to utilize stiffer spinal rods but are at risk of pedicle screw pull-out or neurologic problems from aggressive correction. The authors have manufactured a nickel-titanium rod (NTR) with super-elastic properties to allow gradual correction. The objective of this randomized controlled trial is to evaluate the safety and efficacy of NTR as compared to traditional rods (TRs). METHODS: Patients with adolescent idiopathic scoliosis (AIS) and Lenke 1 curves were randomized (1:1) at surgery to receive either the NTR or TR. Anteroposterior and lateral standing radiographs were obtained preoperative, postoperative day 1 and 7, week 4, 12 and 24, year 1, 2 and 5. Parameters assessed include primary and secondary Cobb angles, kyphosis, rib hump, truncal shift, listing, shoulder height, clavicle angle and T1 tilt. Sagittal profiles were subcategorized into Types A (<25°), B (25-35°) and C (>35°). SRS-30 scores, nickel serum levels and any adverse effects or complications were noted. RESULTS: Twenty-four patients with AIS (mean age: 15 years) were recruited with minimum 5 years follow-up. All radiographic parameters were similar between the two groups. Unlike TR, the NTR group had 33% of subjects with preoperative A profiles become B or C at 5-year follow-up. Nickel levels remained normal, there were no allergic reactions, wound complications, loss of balance, implant breakages or non-union. CONCLUSIONS: This randomized pilot trial showed that the NTR has potential to gradually correct the spinal curve over time, result in comparable correction to TR and may improve sagittal correction.