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Acetabular Revision Using a Bilobed Cementless Component in
Patients with Acetabular Bone Stock Deficiency
Wei-Ming Chen, M.D., C. Anderson Engh Jr., M.D., Robert H. Hopper, Jr., Ph.D., James P. McAuley, M.D., Charles A. Engh, M.D.
The Journal of Bone and Joint Surgery 82:197-206 (2000) © 2000
Background: Massive deficiency of acetabular bone stock is a challenging problem in the increasing number of patients who require revision of failed hip arthroplasty. The bilobed cup has been presented as one alternative technique for cases in which a porous-coated hemisphere cannot be used. The purpose of this study was to assess the results of a bilobed cementless acetabular component for revision reconstruction in hips with acetabular bone deficiency, to clarify indications for its use, and identify factors that influenced the clinical and radiographic outcome.
Methods: 41 hips in 38 patients underwent an acetabular revision with a bilobed, cementless acetabular component. These cases are a subset of 414 acetabular revisions performed during the same time frame. One patient was lost to follow-up and one died during the study period. Two patients who could not return for radiographic evaluation completed questionnaires. The remaining 34 patients (37 hips) were evaluated radiographically and clinically and had an average follow-up of 41 months (range, 24 to 66 months).
Results: Radiographic analysis showed an improvement in the average vertical displacement of the hip center. At the latest follow-up examination, 28 of 37 cups (76 per cent) were stable; three (8 per cent) that were probably unstable had a change in screw position but no definite cup migration; and six (16 per cent) were unstable. Eight of the nine loose or probably loose components occurred in patients with cephalad component migration greater than two centimeters and disruption of Kohlerís line on preoperative radiographs. Additionally, cases were more likely to fail when the inferior aspect of the component did not extend to or below the interteardrop line (undersized component).
Conclusions: Based on our early 24% probably or definitely loose rate and the technical difficulties involved, the authors do not recommend the routine use of this component. The only indications for the procedure are acetabular defects in which a porous-coated hemisphere cannot be secured or in which the surgeon desires to correct an elevated hip center. In these cases there must be less than two centimeters of cephalad acetabular component migration or an intact medial wall in cases with greater than two centimeters of cephalad migration. Alternative reconstruction techniques, such as allograft with or without an acetabular cage, are an option for these same cases.