Automated assessment of polyethylene wear in cemented acetabular components using anteroposterior radiographs of total hip replacements

• Published in: Computerized medical imaging and graphics 2008-04, Vol.32 (3), p.221-238
• Main Authors: Stuart Kerrigan, C, McKenna, Stephen J, Ricketts, Ian W, Wigderowitz, Carlos
• Format: Article
• Language: English
• Subjects: Acetabular wear; Acetabulum - diagnostic imaging; Arthroplasty, Replacement, Hip; Cementation; Eccentricity error; Hip Prosthesis; Imaging, Three-Dimensional; Internal Medicine; Monte Carlo Method; Other; Polyethylenes; Prosthesis Design; Prosthesis Failure; Radiographic analysis; Radiographic Image Interpretation, Computer-Assisted - methods; Reproducibility of Results; Risk Assessment; Robust ellipse fitting; Rotation; Total hip replacement
• ISSN: 0895-6111; 1879-0771
• DOI: 10.1016/j.compmedimag.2007.12.002

Abstract Polyethylene wear in the acetabular components of hip prostheses is implicated in loosening and failure. Radiographic measurement of wear is used to identify patients at risk and to assess prosthesis designs. This paper focuses on analysis of prostheses with cemented acetabular cups from anteroposterior (AP) radiographs. The articular surface of the femoral head and the acetabular rim marker are modelled as spherical and circular respectively, resulting in elliptical image projections. Methods for automatically localising these structures in radiographs are presented using robust ellipse fitting and various error functions. Special attention is paid to the acetabular marker since this often projects as a highly eccentric ellipse. Robust fitting enables successful localisation in the presence of clutter without the need for user interaction. Finally, the use of these ellipses as reference structures for wear estimation is investigated and the effect of eccentricity errors is highlighted.