title: Analysis of in vivo corrosion of 316L stainless steel posterior thoracolumbar plate systems: a retrieval study.
abstract: METHODS
  One hundred eighteen patients retrieved 316L stainless steel thoracolumbar plates, of 3 different designs, used for fusion in 60 patients were examined for evidence of corrosion. A medical record review and statistical analysis were also carried out.
  
  
  OBJECTIVE
  This study aims to identify types of corrosion and examine preferential metal ion release and the possibility of statistical correlation to clinical effects.
  
  
  BACKGROUND
  Earlier studies have found that stainless steel spine devices showed evidence of mild-to-severe corrosion; fretting and crevice corrosion were the most commonly reported types. Studies have also shown the toxicity of metal ions released from stainless steel corrosion and how the ions may adversely affect bone formation and/or induce granulomatous foreign body responses.
  
  
  METHODS
  The retrieved plates were visually inspected and graded based on the degree of corrosion. The plates were then analyzed with optical microscopy, scanning electron microscopy, and energy dispersive x-ray spectroscopy. A retrospective medical record review was performed and statistical analysis was carried out to determine any correlations between experimental findings and patient data.
  
  
  RESULTS
  More than 70% of the plates exhibited some degree of corrosion. Both fretting and crevice corrosion mechanisms were observed, primarily at the screw plate interface. Energy dispersive x-ray spectroscopy analysis indicated reductions in nickel content in corroded areas, suggestive of nickel ion release to the surrounding biological environment. The incidence and severity of corrosion was significantly correlated with the design of the implant.
  
  
  CONCLUSIONS
  Stainless steel thoracolumbar plates show a high incidence of corrosion, with statistical dependence on device design.
authors.affiliation: Department of Orthopaedic Surgery, William Beaumont Hospital, Royal Oak, MI 48073-6769, USA.
authors.forename: Kamran
authors.initials: K
authors.lastname: Majid
authors.forename: Terence
authors.initials: T
authors.lastname: Crowder
authors.forename: Erin
authors.initials: E
authors.lastname: Baker
authors.forename: Kevin
authors.initials: K
authors.lastname: Baker
authors.forename: Denise
authors.initials: D
authors.lastname: Koueiter
authors.forename: Edward
authors.initials: E
authors.lastname: Shields
authors.forename: Harry N
authors.initials: HN
authors.lastname: Herkowitz
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D001860:Bone Plates; D003343:Corrosion; D020878:Device Removal; D019544:Equipment Failure Analysis; D005260:Female; D006801:Humans; D008297:Male; D008422:Materials Testing; D011474:Prosthesis Design; D013193:Stainless Steel / Q000737:chemistry*; D013499:Surface Properties; D013904:Thoracic Vertebrae / Q000601:surgery*
chemical_list: D001672:Biocompatible Materials; D013193:Stainless Steel