Acetabular revision using grafts and cages.

Principles of acetabular revision include stable bone coverage that can support the new acetabular component, restoration of the anatomy and bone stock for future revisions, and equalization of leg length. Achieving these goals depends on the severity of the pelvic defect. Classification of these acetabular defects is critical to optimal treatment choice. A classification formulated by the authors of this paper and based on proven Severity Instrument methodology has been applied effectively at their institutions after meeting reliability and validation criteria. Approaches to acetabular revision based on this classification have resulted in good outcomes.