title: Development of a model-based Roentgen stereophotogrammetric analysis system to measure polyethylene wear in unicompartmental arthroplasty.
abstract: One of the most important causes of failure in unicompartmental knee replacement (UKR) is polyethylene wear. The aim of this study was to develop and assess a novel Roentgen stereophotogrammetric analysis (RSA)-based method for the measurement of linear wear suitable for UKR. Model-based RSA was used to estimate the linear wear of polyethylene bearings in UKR. A phantom was used to validate the method using in vitro measured bearing thicknesses and the linear wear of ten control bearings was estimated in vivo. Computer aided design (CAD) models for the UKRs were used in the model-based RSA system. There was no statistically significant difference between the estimated and measured bearing thicknesses using the CAD models (p = 0.386). The precision of the linear wear measurement, expressed as the standard deviation of the difference between the estimated and measured bearing thickness was 0.163 mm. The bias (mean difference) was 0.030 mm. The use of RSA to measure in vivo wear in a UKR has been shown to be accurate in a phantom, and has been verified with in vivo measured controls. The technique does not require surgical implantation of marker balls and can be used retrospectively.
authors.affiliation: Biomedical Research Unit, Nuffield Department of Orthopaedics, Rheumatology and Musculoskeletal Sciences, University of Oxford, Nuffield Orthopaedic Centre, Windmill Road, Oxford OX3 7LD, UK.
authors.forename: D J
authors.initials: DJ
authors.lastname: Simpson
authors.forename: B J L
authors.initials: BJ
authors.lastname: Kendrick
authors.forename: B L
authors.initials: BL
authors.lastname: Kaptein
authors.forename: A J
authors.initials: AJ
authors.lastname: Price
authors.forename: D W
authors.initials: DW
authors.lastname: Murray
authors.forename: H S
authors.initials: HS
authors.lastname: Gill
mesh_terms: D019645:Arthroplasty, Replacement, Knee; D017076:Computer-Aided Design; D019544:Equipment Failure Analysis / Q000379:methods*; D006801:Humans; D007717:Knee / Q000000981:diagnostic imaging*; D007720:Knee Prosthesis; D008422:Materials Testing / Q000379:methods*; D008954:Models, Biological; D019047:Phantoms, Imaging; D010780:Photogrammetry / Q000379:methods*; D020959:Polyethylene; D011856:Radiographic Image Enhancement; D011859:Radiography / Q000379:methods*
chemical_list: D020959:Polyethylene