title: In vivo compatibility of Dynesys(®) spinal implants: a case series of five retrieved periprosthetic tissue samples and corresponding implants.
abstract: OBJECTIVE
  To determine whether particulate debris is present in periprosthetic tissue from revised Dynesys(®) devices, and if present, elicits a biological tissue reaction.
  
  
  METHODS
  Five Dynesys(®) dynamic stabilization systems consisting of pedicle screws (Ti alloy), polycarbonate-urethane (PCU) spacers and a polyethylene-terephthalate (PET) cord were explanted for pain and screw loosening after a mean of 2.86 years (1.9-5.3 years). Optical microscopy and scanning electron microscopy were used to evaluate wear, deformation and surface damage, and attenuated total reflectance Fourier transform infrared spectroscopy to assess surface chemical composition of the spacers. Periprosthetic tissue morphology and wear debris were determined using light microscopy, and PCU and PET wear debris by polarized light microscopy.
  
  
  RESULTS
  All implants had surface damage on the PCU spacers consistent with scratches and plastic deformation; 3 of 5 exhibited abrasive wear zones. In addition to fraying of the outer fibers of the PET cords in five implants, one case also evidenced cord fracture. The pedicle screws were unremarkable. Patient periprosthetic tissues around the three implants with visible PCU damage contained wear debris and a corresponding macrophage infiltration. For the patient revised for cord fracture, the tissues also contained large wear particles (>10 μm) and giant cells. Tissues from the other two patients showed comparable morphologies consisting of dense fibrous tissue with no inflammation or wear debris.
  
  
  CONCLUSIONS
  This is the first study to evaluate wear accumulation and local tissue responses for explanted Dynesys(®) devices. Polymer wear debris and an associated foreign-body macrophage response were observed in three of five cases.
authors.affiliation: Institute for Evaluative Research in Medicine, University of Bern, Bern, Switzerland.
authors.forename: M
authors.initials: M
authors.lastname: Neukamp
authors.forename: C
authors.initials: C
authors.lastname: Roeder
authors.forename: S Y
authors.initials: SY
authors.lastname: Veruva
authors.forename: D W
authors.initials: DW
authors.lastname: MacDonald
authors.forename: S M
authors.initials: SM
authors.lastname: Kurtz
authors.forename: M J
authors.initials: MJ
authors.lastname: Steinbeck
mesh_terms: D000328:Adult; D020878:Device Removal; D005260:Female; D005549:Foreign-Body Reaction / Q000473:pathology; D015743:Giant Cells, Foreign-Body / Q000473:pathology; D006801:Humans; D008264:Macrophages / Q000473:pathology; D008297:Male; D008853:Microscopy; D008875:Middle Aged; D065289:Pedicle Screws; D011076:Polycarboxylate Cement; D011093:Polyethylene Terephthalates; D019736:Prostheses and Implants; D011475:Prosthesis Failure; D017550:Spectroscopy, Fourier Transform Infrared; D013131:Spine / Q000601:surgery*
chemical_list: D011076:Polycarboxylate Cement; D011093:Polyethylene Terephthalates; C005506:polycarbonate