A ramdomized controlled trial assessing the safety and efficacy of a novel superelastic rod in comparison to conventional titanium rod for scoliosis curve correction

Abstract

SUMMARY: By use of a novel superelastic nitinol rod, we were able to demonstrate in a randomized controlled trial that it has the same safety profile as standard titanium rods, but can result in a superior degree of correction in both the sagittal and coronal plane in patients with Adolescent Idiopathic Scoliosis. INTRODUCTION: Current implant technologies correct scoliosis at the time of surgery and thus are unable to overcome viscoelastic properties of the spine. If this can be achieved, in a similar manner to the Ilizarov technique, superior correction may be possible. A novel superelastic nitinol rod that can maximize curve correction by gradually correcting scoliosis after surgery has been developed by the authors. This is a parallel, double-blinded, randomized controlled trial comparing the safety and efficacy of these nitinol rods (Group 1) to conventional titanium rods (Group 2). METHODS: Twenty-three adolescent idiopathic scoliosis (AIS) subjects, with mean age of 15 years, were recruited. All subjects had single thoracic curves and were randomized at the time of surgery to receive either the nitinol rods or conventional rods. Assessments were carried out based on preoperative anteroposterior and lateral standing and fulcrum bending radiographs, postoperative standing radiographs, and serum nickel levels. All assessments were made by two blinded observers. RESULTS: Eleven subjects were in Group 1 and 12 in Group 2. All subjects were followed for a minimum of 12 months and a mean of 24 months. Mean preoperative Cobb angles in Group 1 and Group 2 were 58.18° and 53.51° respectively, while mean post-operative Cobb angles at 6 months were 17.79° and 16.70° respectively. The fulcrum bending correction index of group 1 subjects improved a mean of 6% from post-operative week 1 to week 24 while that of group 2 subjects improved a mean of 3% within the same time. Of those subjects who had abnormal pre-operative sagittal alignments, 80% from group 1 improved by post-operative week 4, while 67% from group 2 subjects improved. Balance parameters, nickel levels, and complication rates did not differ significantly. CONCLUSION: This is the first study to demonstrate that the novel superelastic rods are safe, can gradually correct curves after surgery, ultimately resulting in better coronal and sagittal alignments compared to traditional rods. Larger multi-center trials are needed to further substantiate these findings.