title: Rod fracture after long construct fusion for spinal deformity: clinical and radiographic risk factors.
abstract: BACKGROUND
  No reports have been published on detailed risk factors for rod fracture after spinal deformity correction and fusion. The purpose of this study was to analyze clinical and radiographic risk factors of rod fracture after long construct fusion for spinal deformity.
  
  
  METHODS
  The survey subjects were 155 cases who were diagnosed with spinal deformity and underwent correction and fusion surgery with long construct instrumentation (>3 levels, average 10.3 levels) between July 2004 and June 2010. The subjects comprised 32 males and 123 females with a mean age of 19.0 (range 8-78) years. The mean Cobb angle was 61.0 ± 16.1° preoperatively and 25.7 ± 16.9° postoperatively. Univariate analysis and logistic regression analysis were performed.
  
  
  RESULTS
  Rod fracture occurred in 8 of 155 cases (5.2 %). The mean period from surgery to rod fracture was 18.1 months (range 2-37). The level of fracture ranged from the thoracolumbar junction to the lumbosacral vertebrae. Six patients had fracture near the fused lower end and two patients had fracture at the thoracolumbar junction. Univariate analysis revealed that non-ambulatory status, preoperative kyphosis, small-diameter rods, multiple surgery, and use of iliac screws were significant risk factors for rod fracture. Sex, obesity, severity of preoperative scoliosis, and rod material were not significant risk factors. Logistic regression analysis revealed that use of iliac screws (odds ratio: 81.9, 95 % confidence interval: 7.2-935.0, p < 0.001) and small-diameter (<6 mm) rods (odds ratio: 16.3, 95 % confidence interval: 1.7-152.6, p = 0.015) were risk factors for rod fracture.
  
  
  CONCLUSIONS
  The incidence of rod fracture after long construct fusion for spinal deformity was 5.2 %. Iliac screw fixation and small-diameter rods were risk factors for rod fracture.
authors.affiliation: Department of Orthopedic Surgery, Seirei Sakura Citizen Hospital, 2-36-2 Ebaradai, Sakura, Chiba, 285-8765, Japan, cds00350@par.odn.ne.jp.
authors.forename: Tsutomu
authors.initials: T
authors.lastname: Akazawa
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Kotani
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sakuma
authors.forename: Tetsuharu
authors.initials: T
authors.lastname: Nemoto
authors.forename: Shohei
authors.initials: S
authors.lastname: Minami
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D002648:Child; D015331:Cohort Studies; D005260:Female; D006801:Humans; D015994:Incidence; D016268:Internal Fixators / Q000009:adverse effects*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D011475:Prosthesis Failure; D011859:Radiography; D012189:Retrospective Studies; D018570:Risk Assessment; D012600:Scoliosis / Q000000981:diagnostic imaging* / Q000601:surgery*; D012720:Severity of Illness Index; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D018709:Statistics, Nonparametric; D013997:Time Factors; D055815:Young Adult