Antiprotrusio cages for acetabular revision.

The purpose of this review was to explore the results of antiprotrusio cages and present indications for these devices. The role of antiprotrusio cages has had several reassessments in North America during the past decade. Currently, the primary indication for antiprotrusio cages are: (1) circumstances in which a stable, uncemented hemispheric acetabular component cannot be gained; and (2) circumstances in which there is so little remaining host bone that biologic fixation of a porous implant is very unlikely. Antiprotrusio cages have been reported to have a mechanical failure rate between 0% and 15% at midterm followup but most series do not report selective results of using cages only for the most severe bone defects. Key technical points when using antiprotrusio cages include: (1) wide exposure of the acetabular bone while protecting surrounding neurovascular structures; (2) positioning the antiprotrusio cage so as to span from host bone to host bone, thereby bridging acetabular defects; (3) appropriate bone grafting of acetabular bone deficiencies; and (4) secure fixation of the cage with good dome and posterior column support.