Acetabular reconstruction with human and bovine freeze- dried bone grafts and a reinforcement device Rosito R et al. CLINICS 2008;64:509-14 dried bone grafts produced at our Tissue Bank (Hospital de Clínicas de Porto Alegre - TBHCPA) in 51 consecutive acetabular reconstruction procedures. MATERIALS AND METHODS From May 1, 1997 to February 1, 2005, 51 patients with severe type III and IV D’Antonio et al. acetabular defects were consecutively submitted to acetabular reconstruction in revision total hip arthroplasty (RTHA) by the hip surgery team of the Orthopedic Department of the University Hospital – HCPA. Grafts were from a human or bovine source was and were chosen at the time of the procedure according to their availability in the storeroom. Patients were divided into two groups according to the type of graft used. Group 1 (n=26) received freeze-dried grafts from a human source and Group 2 (n=25) received grafts from a bovine source. The human bone was obtained from femoral heads. The bovine bone was obtained from Brazilian cattle, and is believed to be completely free of Bovine Spongiform Encephalopathy (BSE) infection. All bone grafts were processed at the TBHCPA, following our own processing protocol. This process allowed the bone grafts to be produced in a way that retained their major characteristics (proteins and minerals). The preparation method cannot be fully disclosed to protect intellectual property rights. In the process, proteins are denatured with 20% hydrogen peroxide, and this is followed by alcohol extraction of lipids. The end product is composed of minerals (65%) and proteins (27%), and is completely sterilized in an autoclave. The failure of the original arthroplasty was determined to be aseptic in all patients. The type and the extent of the acetabular defects had been determined from preoperative radiographs and intraoperative assessments. All patients, without exception, were followed up until March 1, 2006. Patients were fully informed of the study, which was approved by the Ethics Committee of HCPA, and a written informed consent was obtained. The clinicopathologic characteristics of patients are shown in Table 1. The same surgeon carried out all the operations and the same reconstruction technique was used for each patient. A posterior approach was performed in all cases. The loose prosthesis was removed, and all cement, debris, granulomata and fibrous membrane were completely cleared. The acetabulum cavity was carefully reamed in order to reach the vascular bone bed, and then the acetabulum was reconstructed by cancellous morselized (chip size, approximately 8 mm3) freeze-dried bone. The chips were pressed into acetabulum defects and were carefully condensed. The flanges of the reinforcement device (MDT, 510 Table 1 - Clinicopathologic characteristics of the patients. Features Female Male Mean Age (SD) Type III Type IV Mean follow-up (Mo., SD) 54.7 (29.08) Acetabular Deficiency Human Graft Bovine Graft n = 26 (%) n = 25 (%) 18 (69.2) 8 (30.8) 63.8 (14.7) 16 (61.5) 10 (38.5) 20 (80.0) 5 (20.0) 57.7 (12.3) 49.1 (24.49) 14 (56) 11 (44) P value 0.575 0.116 0.457 0.907 São Paulo, Brazil) were bent into shape to fit the specific anatomy of the acetabular region. The hook of the device was placed under the teardrop portion. The upper flange of the metal ring was screwed to the ilium. This should result in a stable composite, with the load-bearing host bone grafts and the implant with an impacted bone graft located beneath the ring. Afterward, a polyethylene cup was cemented into the acetabular reinforcement device. The amount of bone graft used ranged from 40 to 60 g in all cases. Patient analysis was based upon clinical and radiographic evaluations. The clinical analyses were based on functional criteria established by Merle d’Aubigné and Postel.8 For the radiographic analyses, several subjectively established features such as radiolucency, density, trabecular bone formation and component migration were evaluated.9 A radiographic analysis of bone integration, based on the criteria of Conn et al. was thus developed to establish the bone incorporation of the grafts in the two groups. Each criterion, except migration, received an independent score ranging from 0 to 2 for each of the three zones of De Lee and Chanrley10 in the acetabulum, where 0 was the worst and 2 the best result. The sum of the scores was then, multiplied by three for the acetabulum. For migration, a score of 2, 4 or 6 was established when there was more than 6 mm, 3 to 5 mm, or less than 3 mm of prosthesis displacement, respectively. Therefore, a total of 24 points could be achieved for acetabular assessment. Adequate results were classified as those with a sum of 19 or greater. Statistical analyses were performed using the statistical program SPSS (SPSS Inc. Chicago, IL, USA). Descriptive analyses are presented as the mean, median, standard deviation, minimum and maximum values for quantitative variables, and as percentages for qualitative variables where appropriate. For quantitative variables, the Student’s t-test was used, and in asymmetric situations, the Mann-Whitney U test was used. For the categorical variables, the Pearson’s chi-square or Fisher’s exact test was used to compare the clinical and radiographic characteristics between the two