Multislice computed tomography for evaluating acetabular defects in revision THA.

Acetabular bone defects influence acetabular revision surgery, but plain radiographs provide limited information about the osteolytic lesions. Multislice computed tomography may show the volume and location of osteolytic cavities in patients with failed cups more accurately than plain radiographs. We asked whether multislice computed tomography with metal artifact minimization could calculate the volume and location of pelvic osteolysis associated with a failed cup. We evaluated 60 hips with computed tomography just before cup revision. Resolution and bone contrast were maximized using the 135 kV and 250 mA scan settings. The computed tomography slice thickness was 3 mm and the reconstruction index was 1.5 mm. Bone defects were classified according to the radiographic criteria of Paprosky et al. Radiographs showed acetabular lysis on 33 hips, whereas computed tomography scans showed it on 52 hips. The most frequent locations of osteolysis were the posterior wall and ischium. Radiographs underestimated the extent of the lysis. In most hips, the amount of osteolysis seen on the computed tomography views was greater compared with the radiographs: the average volumetric bone was 37.9 cm3. Multislice computed tomography with metal artifact minimization is more sensitive than plain radiographs for identifying and quantifying osteolysis around the cup.