title: Frequent small distractions with a magnetically controlled growing rod for early-onset scoliosis and avoidance of the law of diminishing returns.
abstract: To assess the effect of frequent small distractions with a magnetically controlled growing rod (MCGR) on spinal length gain and achieved distraction length in children with early-onset scoliosis (EOS), and to determine whether the law of diminishing returns applies to this group of patients with MCGR.
  
  
  
  A consecutive series of 3 males and 4 females with EOS who underwent MCGR implantation at a mean age of 10.2 years and were followed up for a mean of 3.8 years were reviewed. Distraction was aimed at 2 mm monthly. The coronal Cobb angle, T1-S1 length gain, and achieved distraction length were measured at 6-monthly intervals.
  
  
  
  The mean total number of distractions was 31. Four of the patients had problems that may have affected distractions. The mean coronal Cobb angle improved post-operatively and was maintained throughout the follow-up period. The mean T1-S1 length gain and achieved distraction length varied over the follow-up period and did not diminish with repeated lengthening.
  
  
  
  Frequent small distractions with the MCGR for EOS enable T1-S1 and achieved distraction length gain without significant reduction in gain after repeated lengthening.
authors.affiliation: Department of Orthopaedics and Traumatology, The University of Hong Kong, Hong Kong, SAR, China.
authors.forename: Jason Pui Yin
authors.initials: JP
authors.lastname: Cheung
authors.forename: Cora
authors.initials: C
authors.lastname: Bow
authors.forename: Dino
authors.initials: D
authors.lastname: Samartzis
authors.forename: Kenny
authors.initials: K
authors.lastname: Kwan
authors.forename: Kenneth Man Chee
authors.initials: KM
authors.lastname: Cheung
mesh_terms: D000293:Adolescent; D000367:Age Factors; D002648:Child; D005260:Female; D006801:Humans; D016268:Internal Fixators; D059346:Magnets; D008297:Male; D019857:Osteogenesis, Distraction / Q000295:instrumentation*; D012600:Scoliosis / Q000209:etiology / Q000503:physiopathology / Q000601:surgery*; D016896:Treatment Outcome
keywords: magnetics; scoliosis; spine; surgery