Introduction and purpose: The study analyzes the efficiency of multislice computerized tomography with metal artifact reduction to calculate the volume, extent and location of osteolysis around a loosened acetabular shell.

Materials and methods: An assessment was made of 48 hips with a loose shell before they were revised with multislice-CT with metal artifact reduction (Toshiba-MEC CT). The slices were taken at 135 kV and 250 mA in order to maximize resolution and bone contrast. Slice width was 3 mm and the reconstruction index 1.5 mm. The osteolytic lesions found on the CT were compared with simple radiographs. Bone defects were classified using Paprosky’s classification.

Results: Acetabular osteolysis was found in the radiographs of 30 hips and in the CTs of 36. Radiographs under-represented the extent of osteolysis: there were 28 hips with a type 1 radiographic defect and 18 with a type 1 CT defect; 6 and 14 with type 2; 8 and 6 with type 3A; and 6 and 10 with type 3B respectively (Wilcoxon test, p=0.004). The mean volumetric loss of bone defects was 35.4 cm3 . Intraoperative findings confirmed the CT findings.

Conclusions: Multislice CT with metal artifact reduction is more sensitive than simple radiographs when it comes to identifying and quantifying osteolysis around an ace-tabular shell. Since multislice-CT shows us the extent and location of osteolysis, it is of great help at the time of planning a revision of the acetabular shell.