Characteristics of pelvic osteolysis on computed tomography after total hip arthroplasty.

UNLABELLED: We investigated the characteristics of pelvic osteolysis using computed tomography to assess osteolytic patterns associated with five acetabular cup designs. Additionally, we examined the relationship between polyethylene wear and volume of pelvic osteolysis. We measured defect volume on the computed tomography images of 126 hips at a mean of 10.9 years after arthroplasty. Defects were classified as osteolysis if there was: (1) a well-defined sclerotic border, (2) no radiographic evidence that the defect existed before hip arthroplasty, and (3) a clear communication between the defect and the joint space. We identified 225 bone defects in 116 hips. Of these, 184 defects in 101 hips fulfilled our criteria for osteolysis. We found that lesion size and the location of the communication pathways depended on the cup design. Osteolysis occurred primarily through central holes, and occurred only around the rim if there were no holes in the cup. The lesions that communicated only through central holes and those with multiple communications tended to be larger than rim-related lesions. There was a moderate correlation between volumetric polyethylene wear and osteolysis volume. Communication pathways between lesions and the joint space are valuable for diagnosing osteolysis on computed tomography. Lesion volume, location, and type of communication pathway to the joint are influenced by cup design. LEVEL OF EVIDENCE: Therapeutic study, Level IV-1 (retrospective case series). See the Guidelines for Authors for a complete description of levels of evidence.