Kosak R, Antolic V, Pavlovcic V, Kralj-Iglic V, Milosev I, Vidmar G, Iglic A
Department of Orthopaedic Surgery, University Medical Centre, Zaloska 9, SI-1000 Ljubljana, Slovenia.
Skeletal Radiol. 2003 Dec;32(12):679-86. doi: 10.1007/s00256-003-0685-2. Epub 2003 Sep 13.
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.
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.
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.
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.
根据假体头部半径的已知值、线性磨损程度以及从标准前后位X线片确定的线性磨损方向，开发一种用于计算聚乙烯杯体体积磨损的新数学模型。
开发了一种新的数学模型。将这种新数学模型的结果与使用标准的、常用的数学模型所获得的结果进行比较，后者仅考虑假体头部半径和聚乙烯杯体的线性磨损程度。进一步将这两种数学模型的结果与使用流体置换法直接测量体积磨损所获得的结果进行比较。
数学模型比较表明，使用新数学模型计算的平均体积磨损比通过流体置换法确定的平均体积磨损小8.5%，而标准数学模型计算的平均体积磨损高17.5%。因此，新数学模型的结果比标准模型的结果偏差明显更小。
在根据前后位X线片计算体积磨损时，不仅要考虑假体头部半径和线性磨损程度，还要考虑线性磨损的方向。
