title: The effect of metal density in thoracic adolescent idiopathic scoliosis.
abstract: Determine impact of metal density on curve correction and costs in thoracic adolescent idiopathic scoliosis (AIS). Ascertain if increased metal density is required for larger or stiffer curves.
  
  
  
  Multicentre retrospective case series of patients with Lenke 1-2 AIS treated with single-stage posterior only surgery using a standardized surgical technique; constructs using >80 % screws with variable metal density. All cases had >2-year follow up. Outcomes measures included coronal and sagittal radiographic outcomes, metal density (number of instrumented pedicles vs total available), fusion length and cost.
  
  
  
  106 cases included 94 female. 78 Lenke 1. Mean age 14 years (9-26). Mean main thoracic (MT) Cobb angle 63° corrected to 22° (66 %). No significant correlations were present between metal density and: (a) coronal curve correction rates of the MT (r = 0.13, p = 0.19); (b) lumbar curve frontal correction (r = -0.15, p = 0.12); (c) correction index in MT curve (r = -0.10, p = 0.32); and (d) correction index in lumbar curve (r = 0.11, p = 0.28). Metal density was not correlated with change in thoracic kyphosis (r = 0.22, p = 0.04) or lumbosacral lordosis (r = 0.27, p = 0.01). Longer fusions were associated with greater loss of thoracic kyphosis (r = -0.31, p = 0.003). Groups differing by preoperative curve size and stiffness had comparable corrections with similar metal density. The pedicle screw cost represented 21-29 % of overall cost of inpatient treatment depending on metal density.
  
  
  
  Metal density affects cost but not the coronal and sagittal correction of thoracic AIS. Neither larger nor stiffer curves necessitate high metal density.
authors.affiliation: Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham, NG7 2UH, UK. paulrushton@doctors.org.uk.
authors.forename: Paul R P
authors.initials: PR
authors.lastname: Rushton
authors.affiliation: Faculty of Medicine, Menoufia University, Al Minufya, Egypt.
authors.forename: Mahmoud
authors.initials: M
authors.lastname: Elmalky
authors.affiliation: Park Clinic, 4 Gorky Terrace, Kolkata, India.
authors.forename: Agnivesh
authors.initials: A
authors.lastname: Tikoo
authors.affiliation: Park Clinic, 4 Gorky Terrace, Kolkata, India.
authors.forename: Saumyajit
authors.initials: S
authors.lastname: Basu
authors.affiliation: Sheffield Children's Hospital, Western Bank, Sheffield, S10 2TH, UK.
authors.forename: Ashley A
authors.initials: AA
authors.lastname: Cole
authors.affiliation: Centre for Spinal Studies and Surgery, Queen's Medical Centre, Nottingham, NG7 2UH, UK.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Grevitt
mesh_terms: D000293:Adolescent; D000328:Adult; D002648:Child; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008670:Metals / Q000191:economics; D065289:Pedicle Screws / Q000191:economics; D012189:Retrospective Studies; D012600:Scoliosis / Q000191:economics / Q000601:surgery*; D013123:Spinal Fusion / Q000191:economics / Q000295:instrumentation* / Q000379:methods; D013904:Thoracic Vertebrae / Q000601:surgery*; D016896:Treatment Outcome; D006113:United Kingdom; D055815:Young Adult
chemical_list: D008670:Metals
keywords: Adolescent idiopathic scoliosis; Cost analysis; Metal density; Outcomes; Pedicle screws