title: Risk factors and outcomes for catastrophic failures at the top of long pedicle screw constructs: a matched cohort analysis performed at a single center.
abstract: METHODS
  Retrospective review with matched-cohort analysis performed at a single institution.
  
  
  OBJECTIVE
  To determine risk factors and outcomes for acute fractures at the proximal aspect of long pedicle screw constructs.
  
  
  BACKGROUND
  Acute fractures at the top of long segmental pedicle screw constructs (FPSC) can be catastrophic. Substantial surgical increase in lordosis may precipitate this problem. In relation to a matched cohort, we postulated that age, body mass index (BMI), and significant correction of lumbar lordosis would increase risk of FPSC and patients with FPSC would have lesser improvements in outcomes.
  
  
  METHODS
  Thirteen patients who sustained FPSC between 2000 and 2007 were evaluated. During this time, 264 patients aged 40 or older had a spinal fusion from the thoracic spine to the sacrum using an all-pedicle screw construct. A cohort of 31 of these patients without FPSC but with all pedicle screw constructs was matched for diagnosis of positive sagittal imbalance, gender, preoperative C7 sagittal plumb, and number of levels fused.
  
  
  RESULTS
  There was a significant difference in age (P = 0.02) and BMI (P = 0.006) between the matched groups. There was no significant difference in preoperative/postoperative C7 plumb or change in lumbar lordosis between groups. Acute neurological deficit developed in 2 patients; both patients improved substantially after revision surgery. Nine patients underwent proximal extension of the fusion. For 7 of the 13 FPSC patients with bone mineral density data (BMD) available, average T score was-1.73; -0.58 for the matched group (10/31 with bone mineral density data) (P = 0.02).
  
  
  CONCLUSIONS
  Factors that increased the risk of FPSC included obesity and older age. Osteopenia increased the risk as evidenced by BMD (based on 17 patients) and the older age of these patients. There was no statistical difference in clinical improvement between groups based on ODI, but the FPSC group did demonstrate a smaller improvement in ODI score than the matched cohort.
authors.affiliation: Department of Orthopaedic Surgery and Rehabilitation, Loyola University Medical Center, Maywood, IL 60153, USA. poleary@lumc.edu
authors.forename: Patrick T
authors.initials: PT
authors.lastname: O'Leary
authors.forename: Keith H
authors.initials: KH
authors.lastname: Bridwell
authors.forename: Lawrence G
authors.initials: LG
authors.lastname: Lenke
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Good
authors.forename: Mark A
authors.initials: MA
authors.lastname: Pichelmann
authors.forename: Jacob M
authors.initials: JM
authors.lastname: Buchowski
authors.forename: Yongjung J
authors.initials: YJ
authors.lastname: Kim
authors.forename: Jennifer
authors.initials: J
authors.lastname: Flynn
mesh_terms: D000368:Aged; D001863:Bone Screws; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008141:Lordosis / Q000601:surgery; D008161:Lumbosacral Region; D008875:Middle Aged; D011475:Prosthesis Failure; D012189:Retrospective Studies; D012307:Risk Factors; D012447:Sacrum / Q000601:surgery; D013123:Spinal Fusion / Q000295:instrumentation*; D013904:Thoracic Vertebrae / Q000601:surgery; D016896:Treatment Outcome