: With modern fracture management techniques, there is the possibility of anatomic acetabular fracture, the risk of post-traumatic arthritis, and the need for hip arthroplasty. few studies have evaluated outcomes of postponed total hip arthroplasty in acetabular fracture patients. So, the aim of this study was to evaluate the total hip arthroplasty in patients previously treated with internal fixation, to pay more attention to the details of this type of surgery and to minimize surgical complications. In this prospective study 20 patients with secondary degenerative joint disease (DJD) or avascular necrosis (AVN) following Internal Fixation surgery of Acetabular fracture, were enrolled. All subjects underwent a second surgery of Total Hip Arthroplasty during 2010-2013 in Imam Hossein Hospital. The patients were followed up every 6 months. Surgical outcome was measured on the basis of Harris criteria in addition to x-ray studies aimed to assess loosening and heterotopic ossification. 20 patients were involved in our study who had previously undergone surgery due to acetabular fracture. The mean age at the time of surgery was 28.3 ± 0.97 years. Vehicle accidents were the most common mechanism of injury in these patients and most patients suffered from Pos. Column fracture, on average after 0.25± 4.9 years’ patients became candidate for hip replacement surgery due to severe DJD. The patients were followed for a mean duration of 2.85 ± 0.22 years in which surgical complications occurred in two cases; infection was diagnosed in one while the other experienced hematoma. When evaluating the patients based on Harris criteria, most patients had an excellent outcome while a poor outcome was reported in none of the cases. According to our results, hip arthroplasty is an appropriate approach in the treatment of secondary DJD and AVN. It can even lead to optimal results in young patients. KEY WORDS: Total Hip Arthroplasty, Acetabular Fracture, avascular necrosis, complications 1. INTRODUCTION Acetabulum is one of the main weight-bearing joints which is involved in all body movements. Accordingly, it should be quite smooth and step less compatible with the motion of the femur . Acetabular fractures are complex intraarticular injuries that occur in a bimodal distribution, typically in young patients with trauma and severe bleeding and in elderly patients with low energy loss in osteoporosis regulation . Although modern fracture management techniques reduce the almost R. Zandi, et,al, 2020 International Medical Journal 1024 anatomical fractures of these fractures, there is still the risk of post-traumatic arthritis . With the increase in vehicle accidents in recent years, a greater number of cases with pelvic and acetabular fractures have been witnessed. This increased failure amount was typically founded in cemented acetabular components and was ascribable to factors such as the relatively younger population, unusual anatomy after trauma, sclerotic bone bed, loss of acetabular bone stock, and complications involving previous hardware . Previously, heavy and prolonged tractions were used for treating such fractures. In the mentioned procedure given that the anatomic reduction is often not fully reached, it usually results in unsmooth surface of the joint and Degenerative Joint Disease (DJD) and these patients have to undergo hip arthroplasty . However, the high levels of non-union and the level of pelvic discontinuity which need to be improved before hip arthroplasty have to be reported . Moreover, the patients’ bed rest is associated with problems such as bedsores and disability. Therefore, today open surgery with the use of internal fixation is highly recommended . Most available literature has addressed the results of arthroplasty after previous non-surgical treatment of acetabular fractures; reporting good outcomes in 60%-90% of such patients . However, a meta-analysis study showed that 13-44% of patients treated for acetabular fracture with open reduction and internal fixation, developed posttraumatic arthritis. posttraumatic arthritis may have crippling consequences after acetabular fractures, and hip arthroplasty are often needed to correct clinical progression of symptoms . It has also been reported that 9% of acetabular fracture patients required hip arthroplasty surgery on average two years after initial surgery . Topical tissue changes, including scar tissue, bone density changes and infection, can make this surgery a challenging task for surgeons and may eventually make subsequent THA revisions . Unfortunately, this type of surgery is also associated with complications such as DJD and avascular necrosis (AVN) which can be managed by arthroplasty ..