title: Factors affecting modular acetabular ceramic liner insertion: a biomechanical analysis.
abstract: BACKGROUND
  Ceramic liner fracture is a concern in THA. However, it is unclear what factors influence the risk of facture. To study these factors under controlled conditions, we created a laboratory model to avoid fractures in vitro.
  
  
  OBJECTIVE
  We determined (1) whether misaligned liner insertion, acetabular shell deformation, entrapment of soft tissue within the locking taper area, and damage to the taper during engagement of the ceramic liner on the locking taper influenced fracture at light and medium impaction forces; and (2) whether the number and force of impactions affect the locking taper force between the ceramic liner and acetabular shell and fracture of the ceramic liner.
  
  
  METHODS
  Impaction and pushout tests were performed with each of five ceramic inserts in titanium shells per test to simulate clinical intraoperative situations of misaligned inserts (Test 1), deformed shells (Test 2), soft tissue within the locking taper area (Test 3), simulated cup taper damage (Test 4), and a combination of misaligned insert, deformed shells, and simulated taper damage to create an overall worst-case condition (Test 5).
  
  
  RESULTS
  Higher pushout forces occurred with increased impact force and an increased number of strikes. Insert fractures only occurred where inserts were misaligned in the shell. No fractures occurred with deformed shells, soft tissue in the taper, or with simulated taper damage in the absence of misaligned inserts.
  
  
  CONCLUSIONS
  The data suggest a misaligned ceramic insert in an acetabular increases the potential for insert fracture. Shell deformation, soft tissue in the taper, or simulated taper damage seemed well tolerated even with very forceful impaction. Forceful and repetitive impaction is favorable for engagement of the taper and improving pullout strength.
authors: London Health Sciences Centre, University Hospital, B9 006, 339 Windermere Road, London, ON N6A 5A5, Canada. James.McAuley@lhsc.on.ca
authors: James P
authors: JP
authors: McAuley
authors: Douglas A
authors: DA
authors: Dennis
authors: Justin
authors: J
authors: Grostefon
authors: William G
authors: WG
authors: Hamilton
mesh_terms: D000077:Acetabulum / Q000601:surgery*; D019644:Arthroplasty, Replacement, Hip / Q000295:instrumentation*; D001696:Biomechanical Phenomena; D002516:Ceramics; D019544:Equipment Failure Analysis; D006622:Hip Prosthesis; D008422:Materials Testing; D011474:Prosthesis Design; D013314:Stress, Mechanical; D014025:Titanium
chemical_list: D014025:Titanium