Abstract
Aims: The reliability of accurately determining wear in polyethylene cups using plain x-rays has been questioned by many authors. In order to explore the accuracy of wear assessment radiologically, we carried out a radiological-retrieval study in 63 patients undergoing revision THR.
Methods:We retrieved 45 intact polyethylene liners from patients after revision THR. The Linear Wear Depth (LWD) in the cups was assessed radiologically measuring the femoral head eccentricity on the plain non-weight bearing x-ray films. The LWD was assessed in the laboratory using the shadowgraph technique. Statistical analysis was performed using the SPSS® software package.
Results: Themean radiological eccentricity of the femoral head was 2.09±2.17 mm (ranging from 0 to 9.50) and the mean LWD 3.52±1.85 mm (ranging from 0.50 to 9.29). The results of Wilcoxon sign ranks test indicated that this 1.43mm-difference is statistically significant (p< 0.001). The measured wear on the plain x-rays was 40,6% less than the true linear wear measured on the retrieved cup.
Conclusions: It is obvious that the radiological eccentricity of the femoral head underestimates the Linear Wear Depth (“true wear”) quite substantially. That difference could be less if the x-rays had been taken weight bearing.
Theses abstracts were prepared by Professor Dr. Frantz Langlais. Correspondence should be addressed to him at EFORT Central Office, Freihofstrasse 22, CH-8700 Küsnacht, Switzerland.
