CORR Insights(®): Custom Acetabular Cages Offer Stable Fixation and Improved Hip Scores for Revision THA With Severe Bone Defects.

Abstract

T he ideal reconstructive method for the severely deficient acetabulum in revision THA remains unsolved. Severe acetabular deficiencies may be evaluated by the Paprosky et al. [7] grading system from which both the anticipated bony defects and the reconstruction needs may be identified. Fortunately, the incidence of severe acetabular deficiency is low, with a report from the Mayo Clinic finding that Paprosky IIIB defects occurred in only 0.9% of hips (31/3505) undergoing revision acetabular surgery at that tertiary care center between 1969–1995 [1]. Most acetabular reconstructions are performed with a large hemispherical shell with a survivorship range of 94% to 100% at midto long-term followup [2]. For acetabuli with greater bony loss, porous metal augments may be added, allowing the creation of a bony and metal concavity supportive of a hemispherical shell. As the defect worsens, more-elaborate options come into the picture, perhaps including custom acetabular cages (or triflange cups), reconstruction cages, cup-cage constructs, or cup-cup constructs. Surgeons must recognize the high surgical complexity when contemplating using one of these approaches, as complications can be severe, and unrecognized or untreated pelvic discontinuities can result in a high risk of failure. During more than a 10-year period, the authors of the current study reported the surgical treatment of 26 patients (all with Type IIIB defects, four with a pelvic discontinuity) who underwent acetabular reconstruction using a gritblasted titanium custom cage. At a mean followup of 67 months (range, 24 months to 120 months) in 24 patients only one cage was felt to be possibly loose, and the authors reported the appearance of particulate allograft incorporation in 23 of 24 patients. One important caveat of this study is that this was the first revision surgery for all but one patient. We can compare the results in this series to other reports about severe acetabular defects, which used other approaches, namely reconstruction cages, or custom triflange cups. In a single-surgeon series, reconstruction cages failed in 24% of reconstructions at mean 4.6-year followup, with the highest failure rates occurring in 10 hips with American Academy of Orthopaedic Surgeons (AAOS) Type This CORR Insights is a commentary on the article ‘‘Custom Acetabular Cages Offer Stable Fixation and Improved Hip Scores for Revision THA With Severe Bone Defects’’ by Li and colleagues available at: DOI: 10.1007/s11999-015-4587-0. The author certifies that he, or any member of his immediate family, has no funding or commercial associations (eg, consultancies, stock ownership, equity interest, patent/ licensing arrangements, etc.) that might pose a conflict of interest in connection with the submitted article. All ICMJE Conflict of Interest Forms for authors and Clinical Orthopaedics and Related Research editors and board members are on file with the publication and can be viewed on request. The opinions expressed are those of the writers, and do not reflect the opinion or policy of CORR or The Association of Bone and Joint Surgeons. This CORR Insights comment refers to the article available at DOI: 10.1007/s11999015-4587-0.