title: Reassessment of computerized wear measurement for total hip arthroplasty with correction for projectional image distortion: a brief follow-up report.
abstract: BACKGROUND
  Wear of the ultra-high molecular weight polyethylene articular surface has been recognized as a major factor threatening the long-term success of total hip arthroplasty. Manual techniques that have been used to measure femoral head penetration into the polyethylene have been plagued with poor reproducibility and limited accuracy. Using a previously described phantom model simulating an unworn total hip arthroplasty, we previously demonstrated significant limitations in the accuracy of several widely used computerized wear measurement programs. A major component of these inaccuracies is projectional distortion of the femoral head and acetabular shell on the radiograph. These inaccuracies can be "corrected for" mathematically.
  
  
  METHODS
  In the present follow-up study, we evaluated a widely used hip wear measurement software program (Hip Analysis Suite version 8.0.3.0) that corrects for these projectional errors with use of our previously described "zero wear" phantom model. A cementless metal-backed acetabular component was evaluated radiographically at three different cephalocaudad locations with respect to a radiopaque centering target. At all three positions, the cup was aligned in three different angles of planar abduction (35 degrees , 45 degrees , 55 degrees ) and four angles of planar anteversion (10 degrees , 20 degrees , 30 degrees , 40 degrees ). The accuracy and reproducibility of Hip Analysis Suite version 8.0.3.0 were determined and compared with the results obtained with the earlier version, Hip Analysis Suite version 4.0.
  
  
  RESULTS
  Hip Analysis Suite version 8.0.3.0 was significantly more accurate than Hip Analysis Suite version 4.0 for determining linear wear and volumetric wear. Hip Analysis Suite version 8.0.3.0 was significantly more accurate for determining femoral head penetration at the different cephalocaudad acetabular positions and over the range of acetabular component anteversion and abduction angles in comparison with Hip Analysis Suite version 4.0.
  
  
  CONCLUSIONS
  With use of the same methodology that was used to evaluate earlier versions of Hip Analysis Suite, the present study showed improvement in the accuracy of wear measurement with Hip Analysis Suite version 8.0.3.0 as compared with Hip Analysis Suite version 4.0.
  
  
  CONCLUSIONS
  On the basis of the results of the present study, Hip Analysis Suite version 8.0.3.0 appears to fulfill the needs for a user-friendly, efficient, and accurate method of assessment of polyethylene wear following total hip arthroplasty.
authors.affiliation: Department of Orthopaedic Surgery, University Hospitals Case Medical Center, 11100 Euclid Avenue, Cleveland, OH 44106, USA. matthew.kraay@uhhospitals.org
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Kraay
authors.forename: Rebecca D
authors.initials: RD
authors.lastname: Moore
authors.forename: John M
authors.initials: JM
authors.lastname: Martell
authors.forename: Clare M
authors.initials: CM
authors.lastname: Rimnac
mesh_terms: D019644:Arthroplasty, Replacement, Hip; D019544:Equipment Failure Analysis / Q000295:instrumentation*; D005270:Femur Head / Q000000981:diagnostic imaging; D006621:Hip Joint / Q000000981:diagnostic imaging*; D006622:Hip Prosthesis; D006801:Humans; D019047:Phantoms, Imaging; D011095:Polyethylenes; D011474:Prosthesis Design; D011475:Prosthesis Failure; D011859:Radiography; D015203:Reproducibility of Results; D012984:Software; D018709:Statistics, Nonparametric; D013314:Stress, Mechanical; D013499:Surface Properties
chemical_list: D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene