title: Changes in surface topography at the TKA backside articulation following in vivo service: a retrieval analysis.
abstract: OBJECTIVE
  With the advent of modular total knee arthroplasty (TKA) systems, backside wear at the articulation between the ultra-high-molecular-weight-polyethylene (UHMWPE) component undersurface and the tibial baseplate has received increasing attention as a source of clinically significant polyethylene wear debris. The aim of this study was to investigate the reciprocating interface at the TKA undersurface articulation using profilometry after in vivo service. Our null hypothesis was that there would be no discernible pattern or relationship between the metal tibial baseplate and UHMWPE surface profile.
  
  
  METHODS
  A nanoscale analysis of thirty retrieved fixed-bearing TKA explants was performed. Surface roughness (Sa) and skewness (Ssk) were measured on both the UHMWPE component undersurface and the tibial baseplate of explants using a non-contacting profilometer (1 nm resolution). Four pristine unimplanted components of two different designs (Stryker Kinemax and DePuy PFC) were examined for control purposes.
  
  
  RESULTS
  Mean explant baseplate surface roughness was 1.24 μm (0.04-3.01 μm). Mean explant UHMWPE undersurface roughness was 1.16 μm (0.23-2.44 μm). Each explant had an individual roughness pattern with unique baseplate and undersurface UHMWPE surface roughness that was different from, but closely related to, surface topography observed in control implants of the same manufacturer and design. Following in vivo service, UHMWPE undersurface showed changes towards a negative skewness, demonstrating that wear is occurring at the backside interface.
  
  
  CONCLUSIONS
  In vivo loading of the TKA prosthesis leads to measurable changes in surface profile at the backside articulation, which appear to be dependent on several factors including implant design and in vivo duration. These findings are consistent with wear occurring at this surface. Findings of this study would support the use of a polished tibial tray over an unpolished design in total knee arthroplasty with the goal of reducing PE wear by means of providing a smoother backside countersurface for the UHMWPE component.
authors.affiliation: Newcastle Upon Tyne Hospitals Trust, Royal Victoria Infirmary & Freeman Hospital, Newcastle upon Tyne, NE1 4LP, UK. r.holleyman@googlemail.com.|Newcastle University, Newcastle upon Tyne, UK. r.holleyman@googlemail.com.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Holleyman
authors.affiliation: Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Susan C
authors.initials: SC
authors.lastname: Scholes
authors.affiliation: Newcastle Upon Tyne Hospitals Trust, Royal Victoria Infirmary & Freeman Hospital, Newcastle upon Tyne, NE1 4LP, UK.
authors.forename: David
authors.initials: D
authors.lastname: Weir
authors.affiliation: University Hospital of North Durham, Durham, UK.
authors.forename: Simon S
authors.initials: SS
authors.lastname: Jameson
authors.affiliation: Newcastle Upon Tyne Hospitals Trust, Royal Victoria Infirmary & Freeman Hospital, Newcastle upon Tyne, NE1 4LP, UK.
authors.forename: Jim
authors.initials: J
authors.lastname: Holland
authors.affiliation: Newcastle University, Newcastle upon Tyne, UK.
authors.forename: Tom J
authors.initials: TJ
authors.lastname: Joyce
authors.affiliation: Newcastle Upon Tyne Hospitals Trust, Royal Victoria Infirmary & Freeman Hospital, Newcastle upon Tyne, NE1 4LP, UK.|Newcastle University, Newcastle upon Tyne, UK.
authors.forename: David J
authors.initials: DJ
authors.lastname: Deehan
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee / Q000295:instrumentation*; D020878:Device Removal; D019544:Equipment Failure Analysis; D006801:Humans; D007720:Knee Prosthesis; D008670:Metals; D008875:Middle Aged; D020959:Polyethylene; D011095:Polyethylenes; D011474:Prosthesis Design; D011475:Prosthesis Failure; D012086:Reoperation; D013977:Tibia / Q000601:surgery
chemical_list: D008670:Metals; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D020959:Polyethylene
keywords: Backside wear; Knee arthroplasty; Profilometry; Retrieval; Surface properties; Undersurface articulation
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