Introduction. Plain radiograph underestimates the lysis extent while bone defect determines acetabu-lar revision. We determine the multislice computed tomography (CT) efficacy with metal-artifact minimization to calculate the volume, extent and location of lytic lesions around a loose acetabular cup. Patients and Methods. 48 hips with a loose acetabular cup were evaluated before cup revision. Multislice CT scans with metal-artifact minimization (Toshiba-MEC CT) were done. Scans were taken at 135 kV and 250 mA to maximize the resolution and bone contrast. CT slice thickness was 3 mm and reconstruction index 1.5 mm. Evidence of osteolytic lesion on these scans was compared with plain radiographs and with intraoperative findings. Bone defects were classified according to Paprosky. Results. Acetabular lysis were found in the radiographs of 18 hips and in the CT scans of 36 hips. The most frequent locations of osteolysis were medial (32 hips) and posterior walls (23 hips). Radiographs underestimated the extent of the lysis: there were 28 hips with radiographic type 1 defects and 16 hips with CT defects; 6 and 11 with type 2; 8 and 10 with type 3A; and 6 and 11 with type 3B respectively (Wilcoxon test, p< 0.001). The mean volumetric bone loss was 35.4 cm3 . Intraoperative findings confirmed CT findings. Conclusions. Multislice CT scans with metal-artifact minimization is more sensitive for identifying and quantifying osteolysis around the cup than are plain radiographs. Since CT scans allow us to show the extent and location of the osteolysis, they are useful to plan cup revision.

Introduction. Plain radiograph underestimates the lysis extent while bone defect determines acetabular revision. We determine the multislice computed tomography (CT) efficacy with metal-artifact minimization to calculate the volume, extent and location of lytic lesions around a loose acetabular cup.

Patients and Methods. 48 hips with a loose acetabular cup were evaluated before cup revision. Multislice CT scans with metal-artifact minimization (Toshiba-MEC CT) were done. Scans were taken at 135 kV and 250 mA to maximize the resolution and bone contrast. CT slice thickness was 3 mm and reconstruction index 1.5 mm. Evidence of osteolytic lesion on these scans was compared with plain radiographs and with intraoperative findings. Bone defects were classified according to Paprosky.

Results. Acetabular lysis were found in the radiographs of 18 hips and in the CT scans of 36 hips. The most frequent locations of osteolysis were medial (32 hips) and posterior walls (23 hips). Radiographs underestimated the extent of the lysis: there were 28 hips with radiographic type 1 defects and 16 hips with CT defects; 6 and 11 with type 2; 8 and 10 with type 3A; and 6 and 11 with type 3B respectively (Wilcoxon test, p< 0.001). The mean volumetric bone loss was 35.4 cm3 . Intraoperative findings confirmed CT findings.

Conclusions. Multislice CT scans with metal-artifact minimization is more sensitive for identifying and quantifying osteolysis around the cup than are plain radiographs. Since CT scans allow us to show the extent and location of the osteolysis, they are useful to plan cup revision.

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.