[Value of the plain roentgen image and arthrography in diagnosis of loosening of cemented hip endoprostheses].

Radiographic signs of suspected prosthetic hip component loosening were evaluated by comparing them with the intraoperative findings. In 59 surgical procedures for suspected loosening of cemented total hip prostheses preoperative radiographic signs of loosening in plain radiographs and radiographic arthrograms were compared with the intraoperative findings. Radiolucent lines between the interfaces prosthesis/cement and cement/bone in defined zones (Salvati et al. 1976, Gruen et al. 1979) were evaluated. For the acetabular component relevant radiolucent lines were observed only between the interface cement/bone. A radiolucent line > 2 mm in zone 1, > 1 mm in zone 2a, a fracture or a retroversion were shown to be reliable signs for loosening with a specificity of 92%, a sensitivity of 61% and a predictive value of 97% (p < 0.01). For the femoral component a radiolucent line at the cement/bone interface of > 1 mm in any of the single zones 2, 3, 6 or 7 and radiolucent lines of > 0 mm in the combined zones 1 + 2 + 6 + 7 proved to be reliable signs of loosening. At the cement/prosthesis interface of the femoral component a radiolucent line of any width in zone 6 and radiolucent lines in the combined zone 1 + 2 or 1 + 7 proved to be reliable signs for loosening as well as major defects within the cement. The above mentioned signs of femoral component loosening display a specificity of 79%, a sensitivity of 86% and a predictive value of 81% (p < 0.001). Arthrography may be useful as an additional diagnostic means for the acetabular component (7 out of 18 false negative results in the radiograms were true positive in the arthrography. Penetration of the contrast material through all 4 zones yields a specificity of 83%, a sensitivity of 48% and a predictive value of 90% with p > 0.05), whereas for the evaluation of the femoral component loosening the gain of information is marginal compared with plain radiographs (specificity 80%, sensitivity 69% and predictive value 78% with p < 0.01). Hip component loosening can be identified with the above mentioned signs even if there are no previous radiographs available.