title: Damage Patterns at the Head-Stem Taper Junction Helps Understand the Mechanisms of Material Loss.
abstract: Material loss at the taper junction of metal-on-metal total hip arthroplasties has been implicated in their early failure. The mechanisms of material loss are not fully understood; analysis of the patterns of damage at the taper can help us better understand why material loss occurs at this junction.
  
  
  
  We mapped the patterns of material loss in a series of 155 metal-on-metal total hip arthroplasties received at our center by scanning the taper surface using a roundness-measuring machine. We examined these material loss maps to develop a 5-tier classification system based on visual differences between different patterns. We correlated these patterns to surgical, implant, and patient factors known to be important for head-stem taper damage.
  
  
  
  We found that 63 implants had "minimal damage" at the taper (material loss <1 mm3), and the remaining 92 implants could be categorized by 4 distinct patterns of taper material loss. We found that (1) head diameter and (2) time to revision were key significant variables separating the groups.
  
  
  
  These material loss maps allow us to suggest different mechanisms that dominate the cause of the material loss in each pattern: (1) corrosion, (2) mechanically assisted corrosion, or (3) intraoperative damage or poor size tolerances leading to toggling of trunnion in taper.
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London and the Royal National Orthopaedic Hospital, Stanmore, United Kingdom.
authors.forename: Harry S
authors.initials: HS
authors.lastname: Hothi
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London and the Royal National Orthopaedic Hospital, Stanmore, United Kingdom.
authors.forename: Andreas C
authors.initials: AC
authors.lastname: Panagiotopoulos
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London and the Royal National Orthopaedic Hospital, Stanmore, United Kingdom.
authors.forename: Robert K
authors.initials: RK
authors.lastname: Whittaker
authors.affiliation: The Centre for Precision Technologies, University of Huddersfield, Huddersfield, United Kingdom.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Bills
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London and the Royal National Orthopaedic Hospital, Stanmore, United Kingdom.
authors.forename: Rebecca A
authors.initials: RA
authors.lastname: McMillan
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London and the Royal National Orthopaedic Hospital, Stanmore, United Kingdom.
authors.forename: John A
authors.initials: JA
authors.lastname: Skinner
authors.affiliation: Institute of Orthopaedics and Musculoskeletal Science, University College London and the Royal National Orthopaedic Hospital, Stanmore, United Kingdom.
authors.forename: Alister J
authors.initials: AJ
authors.lastname: Hart
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D003343:Corrosion; D005260:Female; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D008297:Male; D061825:Metal-on-Metal Joint Prostheses / Q000009:adverse effects*; D008670:Metals / Q000009:adverse effects; D008875:Middle Aged; D011474:Prosthesis Design; D011475:Prosthesis Failure
chemical_list: D008670:Metals
keywords: corrosion; material loss; metal-on-metal; retrieval; taper; wear