title: Wear and corrosion in retrieved thoracolumbar posterior internal fixation.
abstract: METHODS
  Posterior thoracolumbar spine implants retrieved as part of routine clinical practice over a 2-year period were analyzed to identify wear and corrosion.
  
  
  OBJECTIVE
  Engineering analyses of retrieved posterior instrumentation for indications of performance and failure and correlation of this information with clinical factors.
  
  
  BACKGROUND
  Recent studies have reported spinal instrumentation particulate wear debris and have noted the importance of design considerations at implant connector interfaces.
  
  
  METHODS
  A total of 57 implants were analyzed from patients (39 female, 18 male) whose average age at implantation was 43.9 years (range, 13.7-77.4 years). Time of implantation ranged from 2 months to 13.5 years. The top 3 implantation diagnoses were radiculopathy (33%), scoliosis (30%), and back pain (25%). Metallurgical analyses were performed to characterize the wear and/or corrosion, and fractures of the implants.
  
  
  RESULTS
  Wear was present in 75%, corrosion in 39%, and fractures in 7% of the retrieved implants. Wear and/or corrosion was more prevalent, with respect to the total number of implants retrieved, in implants that had been in service at least 1 year. There was no evidence of corrosion in any of the Ti implants, whereas corrosion was present (with wear) in 58% of the stainless steel (SS) implants. Wear and corrosion were more frequently observed in long rods than in short rods. Implantation times were longer for SS implants than for Ti implants.
  
  
  CONCLUSIONS
  Retrieved rods exhibited corrosion, wear, and fracture, with wear and corrosion mainly located at the interfaces with hooks, screws, or cross-connectors. The mechanisms causing this material loss in situ, as well as what local or systemic responses it may stimulate are of clinical significance and should be studied further.
authors.affiliation: Exponent, Inc., Philadelphia, PA 19104, USA. mvillarraga@exponent.com
authors.forename: Marta L
authors.initials: ML
authors.lastname: Villarraga
authors.forename: Peter A
authors.initials: PA
authors.lastname: Cripton
authors.forename: Stephanie D
authors.initials: SD
authors.lastname: Teti
authors.forename: Duane L
authors.initials: DL
authors.lastname: Steffey
authors.forename: Saki
authors.initials: S
authors.lastname: Krisnamuthy
authors.forename: Todd
authors.initials: T
authors.lastname: Albert
authors.forename: Alan
authors.initials: A
authors.lastname: Hilibrand
authors.forename: Alexander
authors.initials: A
authors.lastname: Vaccaro
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D003343:Corrosion; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000601:surgery*; D008297:Male; D008422:Materials Testing / Q000379:methods* / Q000592:standards*; D008875:Middle Aged; D019736:Prostheses and Implants / Q000592:standards*; D013904:Thoracic Vertebrae / Q000601:surgery*; D013997:Time Factors