[Biological acetabular defect reconstruction in revision hip arthroplasty using impaction bone grafting and an acetabular reconstruction ring].

OBJECTIVE: Management of acetabular bone defects Paprosky types IIa and IIb in revision hip arthroplasty by rebuilding the bone stock using impaction bone grafting, primary stable reconstruction with an acetabular reconstruction ring, and restoring the hip center of rotation to its anatomical position. INDICATIONS: Acetabular segmental or combined structural defects in the superior acetabular dome with superior/lateral hip center migration with intact anterior and posterior columns (Paprosky types IIa, IIb). CONTRAINDICATIONS: Acute or chronic infections, severe acetabular bone defects preventing adequate anchorage of the prosthesis-particularly destruction of the posterior column. SURGICAL TECHNIQUE: Modified transgluteal, lateral approach to the hip joint. Removal of the loose acetabular component. Complete circumferential exposure of the acetabular rim, while maintaining mechanical stability of the remaining bone. Preparation of the homologous spongiosa chips and reconstruction of the acetabular defect in impaction grafting technique. Implantation of the acetabular reconstruction ring and primary stable fixation with cancellous screws in the acetabular dome. Cemented fixation of a polyethylene inlay. POSTOPERATIVE MANAGEMENT: Mobilization on 2 underarm crutches from postoperative day 1. Partial weight bearing with 20 kg for 6 weeks postoperatively. If plain radiographs show unchanged seating of the prosthesis after 6 weeks, loading can be increased by 10 kg/week until full weight bearing is achieved; thrombosis prophylaxis is continued throughout. Limitation of hip flexion to 90° during the first 6 weeks, and no adduction and forced external rotation to avoid dislocation. Avoidance of sports involving jumping and axial impact loading for 12 months. Radiologic checkups after 3, 6, and 12 months and, thereafter, every 2 years.
RESULTS: Analysis between 2008 and 2011 involved 22 consecutive patients with a total of 23 prostheses; the mean follow-up was 38 ± 11 months. Compared to the preoperative evaluation, follow-up yielded a significant improvement in the average Harris Hip Score (82.2 ± 8.7 vs. 44.7 ± 10.7) and the Merle d'Aubigné Score (14.6 ± 1.9 vs. 7.5 ± 1.3). Radiological solid osseointegration of the cup was observed in 21 cases; partial radiolucent lines were seen in 2 cases (9 %) in the zones I-III delineated by DeLee and Charnley. In 21 cases (91 %) radiographs confirmed no measurable migration or displacement of the acetabular component and the bone graft was determined to be incorporated on the basis of osseous consolidation within the grafted area in 20 cases (87 %). During follow-up 3 prosthesis (13 %) required revision.