title: Assessment of symptomatic rod fracture after posterior instrumented fusion for adult spinal deformity.
abstract: BACKGROUND
  Improved understanding of rod fracture (RF) in adult spinal deformity could be valuable for implant design, surgical planning, and patient counseling.
  
  
  OBJECTIVE
  To evaluate symptomatic RF after posterior instrumented fusion for adult spinal deformity.
  
  
  METHODS
  A multicenter, retrospective review of RF in adult spinal deformity was performed. Inclusion criteria were spinal deformity, age older than 18 years, and more than 5 levels posterior instrumented fusion. Rod failures were divided into early (≤12 months) and late (>12 months).
  
  
  RESULTS
  Of 442 patients, 6.8% had symptomatic RF. RF rates were 8.6% for titanium alloy, 7.4% for stainless steel, and 2.7% for cobalt chromium. RF incidence after pedicle subtraction osteotomy (PSO) was 15.8%. Among patients with a PSO and RF, 89% had RF at or adjacent to the PSO. Mean time to early RF (63%) was 6.4 months (range, 2-12 months). Mean time to late RF (37%) was 31.8 months (range, 14-73 months). The majority of RFs after PSO (71%) were early (mean, 10 months). Among RF cases, mean sagittal vertical axis improved from preoperative (163 mm) to postoperative (76.9 mm) measures (P<.001); however, 16 had postoperative malalignment (sagittal vertical axis>50 mm; mean, 109 mm).
  
  
  CONCLUSIONS
  Symptomatic RF occurred in 6.8% of adult spinal deformity cases and in 15.8% of PSO patients. The rate of RF was lower with cobalt chromium than with titanium alloy or stainless steel. Early failure was most common after PSO and favored the PSO site, suggesting that RF may be caused by stress at the PSO site. Postoperative sagittal malalignment may increase the risk of RF.
authors.affiliation: Department of Neurosurgery, University of Virginia, Health Sciences Center, Charlottesville, Virginia 22908, USA. jss7f@virginia.edu
authors.forename: Justin S
authors.initials: JS
authors.lastname: Smith
authors.forename: Christopher I
authors.initials: CI
authors.lastname: Shaffrey
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Ames
authors.forename: Jason
authors.initials: J
authors.lastname: Demakakos
authors.forename: Kai-Ming G
authors.initials: KM
authors.lastname: Fu
authors.forename: Sassan
authors.initials: S
authors.lastname: Keshavarzi
authors.forename: Carol M Y
authors.initials: CM
authors.lastname: Li
authors.forename: Vedat
authors.initials: V
authors.lastname: Deviren
authors.forename: Frank J
authors.initials: FJ
authors.lastname: Schwab
authors.forename: Virginie
authors.initials: V
authors.lastname: Lafage
authors.forename: Shay
authors.initials: S
authors.lastname: Bess
mesh_terms: D000328:Adult; D000368:Aged; D004868:Equipment Failure; D005260:Female; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D010027:Osteotomy / Q000379:methods; D010146:Pain / Q000209:etiology* / Q000601:surgery; D011183:Postoperative Complications / Q000503:physiopathology*; D012189:Retrospective Studies; D013121:Spinal Curvatures / Q000150:complications / Q000601:surgery*; D016103:Spinal Fractures / Q000209:etiology* / Q000601:surgery; D013123:Spinal Fusion / Q000009:adverse effects / Q000295:instrumentation*; D013997:Time Factors; D016896:Treatment Outcome