[Postsurgical computed tomography of uncemented hip arthroplasty]

Presentation of the value of postsurgical computed tomography (CT) to diagnose loosening of uncemented femoral stems.

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.

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.

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.