title: Practical considerations for volumetric wear analysis of explanted hip arthroplasties.
abstract: OBJECTIVE
  Wear debris released from bearing surfaces has been shown to provoke negative immune responses in the recipient. Excessive wear has been linked to early failure of prostheses. Analysis using coordinate measuring machines (CMMs) can provide estimates of total volumetric material loss of explanted prostheses and can help to understand device failure. The accuracy of volumetric testing has been debated, with some investigators stating that only protocols involving hundreds of thousands of measurement points are sufficient. We looked to examine this assumption and to apply the findings to the clinical arena.
  
  
  METHODS
  We examined the effects on the calculated material loss from a ceramic femoral head when different CMM scanning parameters were used. Calculated wear volumes were compared with gold standard gravimetric tests in a blinded study.
  
  
  RESULTS
  Various scanning parameters including point pitch, maximum point to point distance, the number of scanning contours or the total number of points had no clinically relevant effect on volumetric wear calculations. Gravimetric testing showed that material loss can be calculated to provide clinically relevant degrees of accuracy.
  
  
  CONCLUSIONS
  Prosthetic surfaces can be analysed accurately and rapidly with currently available technologies. Given these results, we believe that routine analysis of explanted hip components would be a feasible and logical extension to National Joint Registries. Cite this article: Bone Joint Res 2014;3:60-8.
authors.affiliation: North Tees Explant Centre (NTEC), FarndaleHouse, University Hospital of North Tees, TS19 8PE, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Langton
authors.forename: R P
authors.initials: RP
authors.lastname: Sidaginamale
authors.forename: J P
authors.initials: JP
authors.lastname: Holland
authors.forename: D
authors.initials: D
authors.lastname: Deehan
authors.forename: T J
authors.initials: TJ
authors.lastname: Joyce
authors.forename: A V F
authors.initials: AV
authors.lastname: Nargol
authors.forename: R D
authors.initials: RD
authors.lastname: Meek
authors.forename: J K
authors.initials: JK
authors.lastname: Lord
keywords: Arthroplasty; Coordinate measuring machine; Hip; Metal ions; Volumetric wear; Wear debris