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
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.
KeywordsAdolescent 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).
- 3.Cui G, Watanabe K, Nishiwaki Y, Hosogane N, Tsuji T, Ishii K, Nakamura M, Toyama Y, Chiba K, Matsumoto M (2012) Loss of apical vertebral derotation in adolescent idiopathic scoliosis: 2-year follow-up using multi-planar reconstruction computed tomography. Eur Spine J 21:1111–1120CrossRefPubMedPubMedCentralGoogle Scholar
- 10.Remes V, Helenius I, Schlenzka D, Yrjonen T, Ylikoski M, Poussa M (2004) Cotrel-Dubousset (CD) or Universal Spine System (USS) instrumentation in adolescent idiopathic scoliosis (AIS): comparison of midterm clinical, functional, and radiologic outcomes. Spine (Phila Pa 1976) 29:2024–2030CrossRefGoogle Scholar
- 20.Liu H, Li Z, Li S, Zhang K, Yang H, Wang J, Li X, Zheng Z (2014) Main thoracic curve adolescent idiopathic scoliosis: association of higher rod stiffness and concave-side pedicle screw density with improvement in sagittal thoracic kyphosis restoration. J Neurosurg Spine 22:1–8Google Scholar
- 21.Giudici F, Galbusera F, Zagra A, Wilke H-J, Archetti M, Scaramuzzo L (2017) Determinants of the biomechanical and radiological outcome of surgical correction of adolescent idiopathic scoliosis surgery: the role of rod properties and patient characteristics. Eur Spine J. doi: 10.1007/s00586-017-5148-x Google Scholar
- 28.Newton PO, Yaszay B, Upasani VV, Pawelek JB, Bastrom TP, Lenke LG, Lowe T, Crawford A, Betz R, Lonner B, Harms Study G (2010) Preservation of thoracic kyphosis is critical to maintain lumbar lordosis in the surgical treatment of adolescent idiopathic scoliosis. Spine (Phila Pa 1976) 35:1365–1370CrossRefGoogle Scholar
- 32.Lehman RA Jr, Lenke LG, Keeler KA, Kim YJ, Buchowski JM, Cheh G, Kuhns CA, Bridwell KH (2008) Operative treatment of adolescent idiopathic scoliosis with posterior pedicle screw-only constructs: minimum three-year follow-up of one hundred fourteen cases. Spine (Phila Pa 1976) 33:1598–1604CrossRefGoogle Scholar
- 37.Liu XM, Wu SL, Chan YL, Chu PK, Chung CY, Chu CL, Yeung KW, Lu WW, Cheung KM, Luk KD (2007) Surface characteristics, biocompatibility, and mechanical properties of nickel–titanium plasma-implanted with nitrogen at different implantation voltages. J Biomed Mater Res A 82:469–478CrossRefPubMedGoogle Scholar
- 43.Yeung KW, Poon RW, Chu PK, Chung CY, Liu XY, Lu WW, Chan D, Chan SC, Luk KD, Cheung KM (2007) Surface mechanical properties, corrosion resistance, and cytocompatibility of nitrogen plasma-implanted nickel–titanium alloys: a comparative study with commonly used medical grade materials. J Biomed Mater Res A 82:403–414CrossRefPubMedGoogle Scholar
- 44.Yeung KW, Poon RW, Liu XY, Ho JP, Chung CY, Chu PK, Lu WW, Chan D, Cheung KM (2005) Corrosion resistance, surface mechanical properties, and cytocompatibility of plasma immersion ion implantation-treated nickel–titanium shape memory alloys. J Biomed Mater Res A 75:256–267CrossRefPubMedGoogle Scholar
- 45.Yeung KW, Poon RW, Liu XY, Ho JP, Chung CY, Chu PK, Lu WW, Chan D, Cheung KM (2005) Investigation of nickel suppression and cytocompatibility of surface-treated nickel–titanium shape memory alloys by using plasma immersion ion implantation. J Biomed Mater Res A 72:238–245CrossRefPubMedGoogle Scholar
- 50.Samartzis D, Leung Y, Shigematsu H, Natarajan D, Stokes O, Mak KC, Yao G, Luk KD, Cheung KM (2015) Selection of fusion levels using the fulcrum bending radiograph for the management of adolescent idiopathic scoliosis patients with alternate level pedicle screw strategy: clinical decision-making and outcomes. PLoS One 10:e0120302CrossRefPubMedPubMedCentralGoogle Scholar
- 52.Yao G, Cheung JP, Shigematsu H, Ohrt-Nissen S, Cheung KM, Luk KD, Samartzis D (2016) Characterization and predictive Value of “Segmental Curve Flexibility” in adolescent idiopathic scoliosis patients. Spine (Phila Pa 1976) (In Press)Google Scholar
- 60.Lowenstein JE, Matsumoto H, Vitale MG, Weidenbaum M, Gomez JA, Lee FY, Hyman JE, Roye DP Jr (2007) Coronal and sagittal plane correction in adolescent idiopathic scoliosis: a comparison between all pedicle screw versus hybrid thoracic hook lumbar screw constructs. Spine (Phila Pa 1976) 32:448–452CrossRefGoogle Scholar
- 61.Vora V, Crawford A, Babekhir N, Boachie-Adjei O, Lenke L, Peskin M, Charles G, Kim Y (2007) A pedicle screw construct gives an enhanced posterior correction of adolescent idiopathic scoliosis when compared with other constructs: myth or reality. Spine (Phila Pa 1976) 32:1869–1874CrossRefGoogle Scholar