title: Inter- and intraobserver assessment of periacetabular osteodensitometry after cemented and uncemented total hip arthroplasty using computed tomography.
abstract: BACKGROUND
  This study was initiated to evaluate the reproducibility of a novel method for measuring the periacetabular bone density after insertion of cemented and uncemented acetabular cups using CT in vivo.
  
  
  METHODS
  CT scans were obtained from 20 patients after cemented polyethylene cup implantation (ZCA, Zimmer, USA) and 20 patients after uncemented titanium alloy cup fixation (Cerafit, Ceraver, France). A manual segmentation of cancellous and cortical pelvic bone ventral, dorsal and cranial to the cup was undertaken. Values are given in Hounsfield units. Inter- and intraobserver studies were conducted using a special analysis software tool. To define the reproducibility of the method, all measurements were evaluated according to Bland and Altman.
  
  
  RESULTS
  For both cemented and uncemented acetabular cups, reproducibility of bone density measurement for cortical and cancellous bone cranial, ventral and dorsal to the cup was high. There was no significant difference between the intraobsever study (two repeated measurements) and the interobserver study (two investigators), indicating the reproducibility of the method independent of the investigator.
  
  
  CONCLUSIONS
  In conclusion, the periacetabular bone density measurement as conducted in this CT study is a new reproducible method for in vivo evaluation of cortical and cancellous pelvic bone after cemented and uncemented acetabular cup implantation. In vivo CT measurements will allow a thorough assessment of periacetabular stress-shielding phenomena.
authors.affiliation: Department of Orthopaedics, University of Erlangen-Nuernberg, Rathsberger Str. 57, 91054 Erlangen, Germany. rainer.schmidt@ortho.med.uni-erlangen.de
authors.forename: Rainer
authors.initials: R
authors.lastname: Schmidt
authors.forename: Rocco Paolo
authors.initials: RP
authors.lastname: Pitto
authors.forename: Alexander
authors.initials: A
authors.lastname: Kress
authors.forename: Cornelia
authors.initials: C
authors.lastname: Ehremann
authors.forename: Tobias Eckhard
authors.initials: TE
authors.lastname: Nowak
authors.forename: Udo
authors.initials: U
authors.lastname: Reulbach
authors.forename: Raimund
authors.initials: R
authors.lastname: Forst
authors.forename: Lutz
authors.initials: L
authors.lastname: Müller
mesh_terms: D000077:Acetabulum; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D019644:Arthroplasty, Replacement, Hip; D001843:Bone Cements; D015519:Bone Density / Q000502:physiology*; D005260:Female; D006622:Hip Prosthesis; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D010384:Pelvic Bones / Q000503:physiopathology*; D015203:Reproducibility of Results; D014057:Tomography, X-Ray Computed
chemical_list: D001843:Bone Cements