title: The radiographic and imaging characteristics of porous tantalum implants within the human cervical spine.
abstract: METHODS
  Seven cadaveric cervical spines were implanted with a porous tantalum spacer and a titanium alloy spacer, and their radiographic and imaging characteristics were evaluated.
  
  
  OBJECTIVE
  To determine the radiographic characteristics of porous tantalum and titanium implants used as spacers in the cervical spine.
  
  
  BACKGROUND
  Anterior decompressive surgery of the disc space or the vertebral body creates a defect that frequently is repaired with autologous bone grafts to promote spinal fusion. Donor site morbidity, insufficient donor material, and additional surgical time have spurred the development of biomaterials to replace or supplement existing spinal reconstruction techniques. Although the promotion of a solid bony fusion is critical, the implanted biomaterial should be compatible with modern imaging techniques, should allow visualization of the spinal canal and neural foramina, and should permit radiographic assessment of bony ingrowth.
  
  
  METHODS
  Cadaveric spines containing the implants were imaged with plain radiography, computerized tomography, and magnetic resonance imaging. The image distortion produced by the implants was determined qualitatively and quantitatively.
  
  
  RESULTS
  The tantalum and titanium spacers were opaque on plain radiographic films. On computed tomographic scans, more streak artifact was associated with the tantalum implants than with the titanium. On magnetic resonance imaging, the porous tantalum implant demonstrated less artifact than did the titanium spacer on T1- and T2-weighted spin echo and on T2*-weighted gradient-echo magnetic resonance images. Overall, the tantalum implant produced less artifact on magnetic resonance imaging than did the titanium spacer and therefore allowed for better visualization of the surrounding bony and neural structures.
  
  
  CONCLUSIONS
  The material properties of titanium and porous tantalum cervical interbody implants contribute to their differential appearance in different imaging methods. The titanium implant appears to image best with computed tomography, whereas the porous tantalum implant produces less artifact than does the titanium implant on several magnetic resonance imaging sequences.
authors.affiliation: Department of Neurosurgery, University of Miami, Florida, USA.
authors.forename: A D
authors.initials: AD
authors.lastname: Levi
authors.forename: W G
authors.initials: WG
authors.lastname: Choi
authors.forename: P J
authors.initials: PJ
authors.lastname: Keller
authors.forename: J E
authors.initials: JE
authors.lastname: Heiserman
authors.forename: V K
authors.initials: VK
authors.lastname: Sonntag
authors.forename: C A
authors.initials: CA
authors.lastname: Dickman
mesh_terms: D016477:Artifacts; D002102:Cadaver; D002574:Cervical Vertebrae / Q000000981:diagnostic imaging* / Q000601:surgery; D006801:Humans; D008279:Magnetic Resonance Imaging; D016062:Porosity; D019736:Prostheses and Implants; D019919:Prosthesis Implantation; D013123:Spinal Fusion / Q000295:instrumentation*; D013635:Tantalum; D014025:Titanium; D014057:Tomography, X-Ray Computed
chemical_list: D013635:Tantalum; D014025:Titanium