Most acetabular revisions are managed with cementless hemispherical or elliptical metal implants relying on bone ingrowth. Nonetheless, loss of acetabular bone stock and inability to achieve secure component fixation represent challenges in the setting of revision total hip arthroplasty. Impaction bone grafting (IBG) using allograft represents one option for treatment of this problem. However, cup migration and bone graft resorption are limitations when IBG is used for large segmental defects, and the precise role of IBG as well as the use of mesh (and the kinds of defects for which mesh does not work well) in this setting remains unknown.Questions/purposes
We therefore evaluated patients undergoing acetabular revision surgery using IBG and a cemented cup in large bone defects to determine (1) the frequency with which the hip center could be restored in hips with Paprosky 3A and 3B defects and in hips with or without the use of metallic mesh during surgery; (2) survivorship of IBG acetabular-revision reconstructions in patients with severe Paprosky 3A and 3B defects; and (3) risk factors for failure of the reconstruction, including the use of mesh and defect severity (3A versus 3B).Methods
Between 1997 and 2009, we performed 226 acetabular revisions using IBG. During that time, indications for using IBG in this setting included Paprosky 3A and 3B defects without pelvic discontinuity. Of these, 204 (90.2%) were available for followup at a minimum of 5 years (mean, 10 years; range, 5-17 years). There were 100 hips with an intraoperative bone defect of Paprosky 3A and 104 with a 3B. Medial or rim acetabular uncontained defects were treated with medial and/or lateral metallic mesh in 142 hips. We determined the postoperative radiological cup position and acetabular reconstruction of the hip center according to Ranawat in both groups. We assessed the appearance of cup loosening and the possible risk factors with regression analysis.Results
Mean postoperative acetabular abduction angle and vertical, horizontal, and hip rotation center distances improved (p < 0.001 in all parameters). Nine hips showed radiological loosening in the group with bone defect 3A and 16 in Group 3B. The survival rate for loosening at 15 years was 83% (95% confidence interval [CI], 71%-95%) for Group 3A and 73% (95% CI, 60%-84%) for Group 3B (p = 0.04). The survivorship for loosening when using mesh or not at 15 years was: no mesh 89% (95% CI, 74%-99%), medial mesh 85% (95% CI, 72%-97%), lateral mesh 80% (95% CI, 67%-91%), and medial and lateral meshes 54% (95% CI, 31%-76%) (p = 0.008). After controlling the most relevant confounding variables we found that the most important factor associated with loosening was lateral mesh use (p = 0.008; hazard ratio, 2.942; 95% CI, 1.328-6.516).Conclusions
IBG provides an improvement in reconstruction of the hip rotation center in acetabular revision surgery. Although results are good for contained or medial large defects, hips with a rim or lateral segmental defect may need other options for reconstruction of these challenging surgeries.Level of Evidence
Level III, therapeutic study.