BACKGROUND: The incidence of posttraumatic arthrosis after acetabular fractures is significant, and patients frequently require secondary total hip arthroplasty. Conversion arthroplasty is more technically difficult, and there is higher risk than with routine primary total hip arthroplasty. The goal of this study was to identify the challenges and risks of secondary total hip arthroplasty compared to primary total hip arthroplasty. METHODS: We retrospectively identified 30 patients who underwent secondary total hip arthroplasty after open reduction and internal fixation of an acetabulum fracture and compared them with 20 patients who had undergone primary total hip arthroplasty for degenerative joint disease. RESULTS: Demographic data were similar between groups. Hardware removal was deemed necessary in 21 patients (70%). Allograft was needed for bone defects in 33% of secondary total hip arthroplasty cases, while no primary cases required grafting. Operative time (217.4 vs. 113.7 min, P < 0.01) and estimated blood loss (875.8 vs. 365 mL, P < 0.01) were significantly greater in the secondary arthroplasty group. Early postoperative complications were also higher in the secondary arthroplasty group. CONCLUSIONS: Total hip arthroplasty after acetabular fracture open reduction and internal fixation is a more complex procedure due to exposure difficulty, possible implant removal, management of bony deficits, and the potential use of cages and revision components. Experienced surgeons managing these complicated cases must take great care not only in ensuring appropriate technique but also in appropriate patient education regarding increased risk of major and minor complications. LEVEL OF EVIDENCE: Level III.