European Spine Journal

, Volume 27, Issue 2, pp 327–339 | Cite as

A randomized double-blinded clinical trial to evaluate the safety and efficacy of a novel superelastic nickel–titanium spinal rod in adolescent idiopathic scoliosis: 5-year follow-up

  • Jason Pui Yin Cheung
  • Dino Samartzis
  • Kelvin Yeung
  • Michael To
  • Keith Dip Kei Luk
  • Kenneth Man-Chee Cheung
Original Article



To evaluate the safety and efficacy of a superelastic shape-memory alloy (SNT) rod used in the treatment of adolescent idiopathic scoliosis (AIS).


AIS Patients with Lenke 1 curves undergoing fusion surgery were randomized (1:1) at the time of surgery to receive either the SNT or a conventional titanium alloy (CTA) rod. Radiographs were obtained preoperatively and postoperatively up to 5 years of follow-up. Parameters assessed included coronal and sagittal Cobb angles, and overall truncal and shoulder balance. Sagittal profiles were subcategorized into Types A (<20°), B (20–40°), and C (>40°).


Twenty-four patients with mean age of 15 years were recruited. A total of 87.0% of subjects were followed up till postoperative 5 years, but all patients had minimum 2 years of follow-up. The fulcrum-bending correction index for the SNT group was 113% at postoperative day 4 and 127% at half-year, while the CTA group was 112% at postoperative day 4 and only 106% at half-year. In terms of sagittal profile, the SNT group moved toward type B profile at half-year follow-up with a mean correction of 7.6°, while no significant change was observed in the CTA group (−0.7°). Nickel levels remained normal, and there were no complications.


This is the first randomized clinical trial of a novel SNT rod for treating patients with AIS, noting it to be safe and has potential to gradually correct scoliosis over time. This study serves as a pilot and platform to properly power future large-scale studies to demonstrate efficacy and superiority.


Adolescent idiopathic scoliosis Superelastic Nickel Titanium Rod 



We would like to thank Dr. Kin Cheung Mak for clinical care of the patients in this study, and Dr. Guneet Makkar from the CTC of HKU for statistical support.

Compliance with ethical standards

Conflict of interest

All the authors declare that they have no conflict of interest.


This study was financially supported by Hong Kong Research Grants Council (HKU 7283/00M and CityU 1/04C); Scoliosis Research Society (9667002); Hong Kong Innovation Technology Fund Tier 2 Grant (GHP 019/05).


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Copyright information

© Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  1. 1.Department of Orthopaedics and TraumatologyThe University of Hong KongHong Kong SARChina

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