title: Monitoring of polyethylene wear in nonmetal-backed acetubular cups by digitized anteroposterior pelvic radiography.
abstract: The aim of this study was to assess polyethylene wear in a total hip prosthesis by digitized radiography of the whole pelvis in the anteroposterior (AP) plane. The three-dimensional (3-D) pose of the nonmetal-backed acetubular cup, materialized by its metal ring and the femoral head made of metal or ceramic, was estimated using iterative algebraic algorithms with inner bias correction and bootstrapping for variance reduction. Points of interest were obtained by maximizing the correlation between sampled density profiles and 3-D geometric models degraded by the modulation transfer function (MTF) of the radiographic system and the film scanner. The error in the maximal correlation estimate were inferred from noise power spectra (NPS) and allowed the calculation of the point covariance matrix. Both NPS and MTF were modeled for each stage and estimated using least-square fitting of the overall NPS model to the autospectral density function calculated in stationary regions. Comparison of the radiographic time series was made possible by the high accuracy level and 3-D matching from the cup orientation. The feasibility of the full 3-D measurement, the assumption of negligible lateral wear and its influence on AP wear are discussed on simulated and real radiographic data.
authors.affiliation: Medical Imaging Research Team (ERIM), Faculty of Medicine, Auvergne University, P.O. Box 38, 63001 Clermont-Ferrand Cedex, France. laurent.sarry@u-clermont1.fr
authors.forename: L
authors.initials: L
authors.lastname: Sarry
authors.forename: C
authors.initials: C
authors.lastname: Tilmant
authors.forename: S
authors.initials: S
authors.lastname: Boisgard
authors.forename: J Y
authors.initials: JY
authors.lastname: Boire
authors.forename: J P
authors.initials: JP
authors.lastname: Levai
mesh_terms: D000077:Acetabulum / Q000000981:diagnostic imaging; D000465:Algorithms; D003198:Computer Simulation; D019544:Equipment Failure Analysis / Q000379:methods*; D005240:Feasibility Studies; D006621:Hip Joint / Q000000981:diagnostic imaging; D006622:Hip Prosthesis / Q000009:adverse effects*; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007593:Joint Instability / Q000000981:diagnostic imaging* / Q000209:etiology*; D008670:Metals; D010388:Pelvis / Q000000981:diagnostic imaging*; D019047:Phantoms, Imaging; D020959:Polyethylene; D011475:Prosthesis Failure; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
chemical_list: D008670:Metals; D020959:Polyethylene