PURPOSE: Presentation of the value of postsurgical computed tomography (CT) to diagnose loosening of uncemented femoral stems. MATERIALS AND METHODS: Incremental CT and spiral CT were performed on six femora with implanted uncemented stems after the entire femora were embedded in polymethylmethacrylate. The femora were subsequently sectioned (thickness 1 mm, separation 8 mm) and the medial and lateral contact areas of the prosthetic stem compared with the CT data. RESULTS: The CT showed a contact of femoral stem and cortical bone between 0.4 mm (3.4 %) and 4.8 mm (47.1 %) and the section specimens between 0.9 mm (8.7 %) and 3.4 mm (36.7 %). No correlation was found between the results (r = 0.61), since the individual differences were up to 24 % in almost all sections. CONCLUSIONS: Neither single-slice nor two-slice CT is capable of demonstrating the direct bone-endoprosthesis contact. Multidetector row CT (MDCT) is conceivably more accurate to measure the cortical contact of the femoral stem.
PURPOSE: Presentation of the value of postsurgical computed tomography (CT) to diagnose loosening of uncemented femoral stems. MATERIALS AND METHODS: Incremental CT and spiral CT were performed on six femora with implanted uncemented stems after the entire femora were embedded in polymethylmethacrylate. The femora were subsequently sectioned (thickness 1 mm, separation 8 mm) and the medial and lateral contact areas of the prosthetic stem compared with the CT data. RESULTS: The CT showed a contact of femoral stem and cortical bone between 0.4 mm (3.4 %) and 4.8 mm (47.1 %) and the section specimens between 0.9 mm (8.7 %) and 3.4 mm (36.7 %). No correlation was found between the results (r = 0.61), since the individual differences were up to 24 % in almost all sections. CONCLUSIONS: Neither single-slice nor two-slice CT is capable of demonstrating the direct bone-endoprosthesis contact. Multidetector row CT (MDCT) is conceivably more accurate to measure the cortical contact of the femoral stem.