title: Which design and biomaterial factors affect clinical wear performance of total disc replacements? A systematic review.
abstract: BACKGROUND
  Total disc replacement was clinically introduced to reduce pain and preserve segmental motion of the lumbar and cervical spine. Previous case studies have reported on the wear and adverse local tissue reactions around artificial prostheses, but it is unclear how design and biomaterials affect clinical outcomes.
  
  
  OBJECTIVE
  Which design and material factors are associated with differences in clinical wear performance (implant wear and periprosthetic tissue response) of (1) lumbar and (2) cervical total disc replacements?
  
  
  METHODS
  We performed a systematic review on the topics of implant wear and periprosthetic tissue response using an advanced search in MEDLINE and Scopus electronic databases. Of the 340 references identified, 33 were retrieved for full-text evaluation, from which 16 papers met the inclusion criteria (12 on lumbar disc replacement and five on cervical disc replacement; one of the included studies reported on both lumbar and cervical disc replacement), which involved semiquantitative analysis of wear and adverse local tissue reactions along with a description of the device used. An additional three papers were located by searching bibliographies of key articles. There were seven case reports, three case series, two case-control studies, and seven analytical studies. The Methodological Index for Non-randomized Studies (MINORS) Scale was used to score case series and case-control studies, which yielded mean scores of 10.3 of 16 and 17.5 of 24, respectively. In general, the case series (three) and case-control (two) studies were of good quality.
  
  
  RESULTS
  In lumbar regions, metal-on-polymer devices with mobile-bearing designs consistently generated small and large polymeric wear debris, triggering periprosthetic tissue activation of macrophages and giant cells, respectively. In the cervical regions, metal-on-polymer devices with fixed-bearing designs had similar outcomes. All metal-on-metal constructs tended to generate small metallic wear debris, which typically triggered an adaptive immune response of predominantly activated lymphocytes. There were no retrieval studies on one-piece prostheses.
  
  
  CONCLUSIONS
  This review provides evidence that design and biomaterials affect the type of wear and inflammation. However, clinical study design, followup, and analytical techniques differ among investigations, preventing us from drawing firm conclusions about the relationship between implant design and wear performance for both cervical and lumbar total disc replacement.
authors.affiliation: Implant Research Center, Drexel University, 3401 Market Street, Suite 345, Philadelphia, PA, 19104, USA.
authors.forename: Sai Y
authors.initials: SY
authors.lastname: Veruva
authors.forename: Marla J
authors.initials: MJ
authors.lastname: Steinbeck
authors.forename: Jeffrey
authors.initials: J
authors.lastname: Toth
authors.forename: Dominik D
authors.initials: DD
authors.lastname: Alexander
authors.forename: Steven M
authors.initials: SM
authors.lastname: Kurtz
mesh_terms: D001672:Biocompatible Materials; D001696:Biomechanical Phenomena; D002574:Cervical Vertebrae / Q000503:physiopathology / Q000601:surgery*; D005549:Foreign-Body Reaction / Q000209:etiology; D006801:Humans; D007403:Intervertebral Disc / Q000503:physiopathology / Q000601:surgery*; D008159:Lumbar Vertebrae / Q000503:physiopathology / Q000601:surgery*; D008670:Metals; D011108:Polymers; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013314:Stress, Mechanical; D059145:Total Disc Replacement / Q000009:adverse effects / Q000295:instrumentation*; D016896:Treatment Outcome
chemical_list: D001672:Biocompatible Materials; D008670:Metals; D011108:Polymers