Acetabular reconstruction with human and bovine freeze- dried bone grafts and a reinforcement device Rosito R et al. CLINICS 2008;64:509-14 Figure 3 - Immediate post-operative radiography showing the acetabular reconstruction with lyophilized bovine graft and reinforcement device Figure 4 - Anteroposterior radiography of the reconstruction with lyophilized bovine graft and reinforcement device (three-year follow-up) showing sug- gestive signs of bone incorporation, as may be seen by the regularity of medium wall, graft density and absence of radiolucent lines DISCUSSION The problem of hip stability in aged patients is serious 512 and has been the object of many different approaches.12-13 The goals of reconstruction of severe acetabular defects in revision arthroplasty of the hip are to restore the bone stock, to repair the hip mechanics and to obtain stability. The use of bone grafts are imperative in order to achieve these goals. Autografts are an excellent option, but the quantity of autografts is usually limited, and therefore allografts have frequently been used as an alternative. Therefore, a bone bank subject to strict quality control is necessary to minimize the risk of disease transmission. Unfortunately, there is no single technique that currently provides a solution for all deficiencies. Reconstruction with impacted cancellous morselized bone has shown to provide good results,2,14 but we are skeptical about the use of this technique in hostile acetabula, especially those of type III and IV deficiencies.1,4,5,15 Additionally, the reconstruction of structural allografts is still controversial.3 Like other authors, we also consider that the occurrence of a severe acetabular defect reconstruction should be treated with a reinforcement device combined with bone grafts. This method provides initial stability and protects grafts from mechanical stress until graft integration is achieved.4,5 For hip procedures, we believe that the most suitable grafts are those that are unaltered by processing. As assessed by physical and chemical analyses, the freeze-dried bones produced at TBHCPA retained most of their mineral and protein characteristics, and the grafts from bovine and human sources were very similar, although they did not have the same texture and malleability as their deep-frozen counterparts.16 These characteristics enabled proper handling of the freeze-dried bones after rehydration, both from a technical and mechanical viewpoint.17 By the Merle d’Aubigné and Postel criteria, the average results obtained from the human and bovine grafts were considered good and very good in 92% and 80% of the cases, respectively. Although the follow-up may be not be long enough for a more reliable clinical evaluation, it is notable that the use of human and bovine freeze-dried grafts during that period was not harmful to the patients, and there were no significant differences between the two groups. When our results were compared with studies in the literature with similar follow-up periods that used allogeneic deep-frozen grafts instead, we did not find any considerable differences that could be attributed to the use of freeze-dried grafts from bovine or human sources.4,5,15 Several studies have clinically and radiographically evaluated the use of human and bovine freeze-dried grafts in a number of bone diseases and have found that they performed well. However, few indexed articles concerning the use of human or bovine freeze-dried grafts in RTHA have been reported. This reluctance of hip surgeons to