Author/Editor		Košak, R; Antolič, V; Pavlovčič, V; Kralj-Iglič, V; Milošev, I; Vidmar, G; Iglič, A
Title		Polyethylene wear in total hip prostheses: the influence of direction of linear wear on volumetric wear determined from radiographic data
Type		članek
Source		Skeletal Radiol
Vol. and No.		Letnik 32
Publication year		2003
Volume		str. 679-86
Language		eng
Abstract		Purpose. To develop a new mathematical model for calculating the volumetric wear of polyethylene cups from known values of the radius of the prosthesis head, the extent of linear wear and the direction of linear wear determined from standard antero-posterior radiographs. Method. A new mathematical model was developed. The results of this new mathematical model were compared with the results obtained using the standard, frequently used mathematical model, which takes into consideration only the radius of the prosthesis head and the extent of linear wear of the polyethylene cups. The results of both mathematical models were further compared with the results obtained by direct measurement of volumetric wear using the fluid displacement method. Results. Comparison of the mathematical models shows that the average volumetric wear calculated using the new mathematical model is 8.5% smaller than the average volumetric wear determined by the fluid displacement method, while the average volumetric wear calculated by standard mathematical model is 17.5% higher. The results of the new mathematical model are, thus, notably less biased than those of the standard one. Conclusion. In calculating the volumetric wear from antero-posterior radiographs, not only the radius of the prosthesis head and the extent of the linear wear but also the direction of the latter has to be considered.
Descriptors		HIP PROSTHESIS HIP JOINT WEIGHT-BEARING POLYETHYLENES MODELS, THEORETICAL