Reconstruction of Acetabular Bone Deficiencies Using the Antiprotrusio Cage

CHAPTER 50 Reconstruction of Acetabular Bone Deficiencies Using the Antiprotrusio Cage




One of the most challenging aspects of acetabular revision is managing bone loss. Bone loss occurs in a variety of locations, and bony defects are of variable size. The goal is to create a stable construct capable of providing long-term stability of an acetabular component.1


Most acetabular defects can be reconstructed with an uncemented hemispherical cup with screws with or without bone graft. Significant acetabular defects may require structural grafts, a bilobed cup, a trabecular metal cup with or without augments, an acetabular protrusio cage, or a cup-cage construct depending on the type of bone loss.2 An unresolved issue in revision total hip arthroplasty (THA) is acetabular reconstruction when extensive bone loss is significant enough to exceed the limits of large hemispherical cups.3


The antiprotrusio cage (APC) provides a large contact area between the implant and remaining pelvic bone, distributes force over a large area, and decreases the likelihood of implant migration.4 It also allows the treatment of large bone defects with morcelized or bulk bone grafts, bridging gaps in native bone and thus protecting bone graft from forces that might contribute to failure.5 The APC provides fixation above and below areas of pelvic discontinuity, thereby allowing simultaneous treatment of the discontinuity and the failed acetabular component.



RELEVANT SURGICAL ANATOMY


The knowledge of relevant anatomy is essential before any procedure but in particular before placement of an APC.




Nerves






CLASSIFICATION OF ACETABULAR BONE DEFECTS


The American Academy of Orthopedic Surgeons classifies acetabular bone deficiencies into the following five categories (Fig. 50-1)8:








Berry and colleagues9 subclassified the pelvic discontinuity as type IVa if it was associated only with cavitary bone loss, as type IVb if it was associated with segmental or combined (cavitary and segmental) bone loss, and as type IVc if it was associated with previous irradiation of the pelvis with or without cavitary or segmental bone loss.


Paprosky10 classified acetabular defects as follows (Fig. 50-2):



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Mar 10, 2016 | Posted by in Reconstructive surgery | Comments Off on Reconstruction of Acetabular Bone Deficiencies Using the Antiprotrusio Cage

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