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Acetabular Revision With Cup-Cage Constructs
In most acetabular reconstructions, a noncemented hemispheric socket with screw fixation provides acceptable initial stability and contact with host bone. These implants are successful in most patients who have supportive host bone and a reliable ingrowth surface. However, there are limitations to the use of hemispheric porous-coated implants. It may not be possible to achieve adequate stability and host bone contact in patients with massive bone loss, pelvic discontinuity, or pathologic bone. Use of a standard hemispheric socket will have a high anticipated failure rate in such patients. In the 1990s, surgeons began using large anti protrusio cages in patients with massive bone loss, pelvic discontinuity, or pathologic bone. Although they often were successful in attaining initial stability, fracture and early loosening occurred in patients in whom the construct was not adequately supported by graft or host bone. In addition, they had no potential for osseointegration, and the lack of biologic fixation oftenr esulted in mechanical failure in the mid- to long-term. The tantalum cup-cage construct was introduced in 2005. This construct adds biologic fixation to a simple cage in an effort to secure a highly porous, hemispheric metal implant against the maximum amount of native host bone possible and supplement this fixation with a cage. After the cup is placed and stabilized, the cage is placed into the socket and then fixed to the ilium with screws and to the ischium through the inferior flange. The polyethylene liner is cemented into the construct, which secures the liner and unitizes the cup and cage. The well-fixed cage provides initial stability and offloads the cup to promote bone ingrowth. This chapter reviews the indications, contraindications, results, surgical steps, and pitfalls for performing acetabular reconstructions using a cup-cage construct.