PURPOSE OF THE STUDY Tantallum trabecular metal implants (Trabecular Metal Technology - TMT) considerably changed the acetabular reconstruction options in revision surgeries with extensive bone defects and distorted pelvic ring integrity. The purpose of this study is to ascertain the short-term to medium-term outcomes of acetabular reconstruction through TMT implants in patients with Paprosky type 3a and 3b acetabular defects and in case of pelvic discontinuity. MATERIAL AND METHODS The prospective monocentric study included patients in whom the revision of acetabular components in total hip arthroplasty was performed, the acetabular defect was classified as Paprosky 3a and higher, a TMT implant was used for reconstruction, and the follow-up period was at least 2 years after surgery. In total, 87 patients who had met the inclusion criteria were operated on and followed-up. The patients in the study group underwent a clinical examination, an X-ray and also an assessment using the Harris hip score. Moreover, the patients were asked about their satisfaction with the surgical outcome, their willingness to undergo the same procedure again in case of difficulties, and they were also asked to rate the outcome in percentage term and by assigning grades. Also, an analysis of the reasons for revision and subsequent complications was carried out. Implant integration and its migration were evaluated on an X-ray. RESULTS 32 men and 55 women were subjects to evaluation, with a balanced number of operated sides (44:43 in favour of the right side). One-stage procedures prevailed, which were performed in a total of 74 cases, while two-stage revisions were performed in 13 cases in the study group. In three patients (3.5%) pelvic discontinuity was diagnosed, 69 patients (79%) suffered from Paprosky 3a defect and 15 patients (17%) from Paprosky 3b defect. The first patients underwent surgery in 2009 and the mean follow-up period in the study group was 48 months. In 1 patient the TMT implant was removed for infectious complications, in the remaining part of the group the TMT implant was fully integrated with no signs of loosening or migration in the monitored period. In the assessment using the Harris hip score, the mean score of 80.4 (range 36-99) was achieved. When assessing the satisfaction with the surgical outcome, the mean value achieved was 94.4%, and the mean assigned grade was 1.26 (on a school grading scale). DISCUSSION Extensive bone defects and pelvic discontinuity represent an issue in revisions of the acetabular component in total hip arthroplasty. There are several options how to address these conditions. State-of-the-art TMT implants thanks to their shortterm and medium-term outcomes appear as one of the most beneficial option with a low failure rate both in our study group and in published papers. CONCLUSIONS Evaluation of this monocentric prospective study reveals encouraging short-term and medium-term outcomes of the use of TMT implants in managing extensive acetabular bone defects of Paprosky 3a and 3b type and supports their further introduction into practice at our department. Key words: total hip arthroplasty (THA), revision implantation, TMT implant.