BACKGROUND Total hip arthroplasty (THA) is a good option as a salvage procedure after failed treatment of proximal femur fracture. The anatomy of the proximal femur, however, makes this surgery complicated and challenging. The purpose of this study was to evaluate the radiographic and clinical outcomes of THA after failed treatment of proximal femur fractures. METHODS We retrospectively analysed 50 consecutive THAs (42 women, 8 men; mean age 77 years) after failed treatment of a proximal femur fracture. Mean postoperative follow-up was 58.1 months. Preoperative diagnoses were femoral neck fracture in 18 hips and trochanteric fracture in 32 hips, including three that were infected. Failure resulted from cutout in 22 cases, osteonecrosis in 12, non-union with failed fixation in nine, postoperative osteoarthritis in four, and infection in three. Factors compared included radiographic assessment, complication rate, visual analogue scale (VAS), and Harris Hip Scores (HHS). Radiographic variables included femoral neck anteversion and cup and stem alignment. RESULTS Absolute values of the differences in femoral neck anteversion between the affected and healthy sides were 6.0° in the femoral neck fracture group and 19.2° in the trochanteric fracture group (p = 0.01). There were no significant differences in cup anteversion (p = 0.20) or stem anteversion (p = 0.08). The complication rate was significantly higher in the trochanteric fracture group than in the femoral neck fracture group (25 vs 0%, p < 0.0001). Postoperative complications in the trochanteric fracture group included three periprosthetic fractures (9.4%), two dislocations (6.3%), two surgical-site infections (6.3%), and one stem penetration (3.1%). Although no significant differences between groups were seen in the VAS or HHS at final follow-up (p = 0.32, 0.09, respectively), these measures were significantly improved at final follow-up in both groups (p < 0.0001 for both). CONCLUSIONS Performing THA after failed treatment of trochanteric fractures requires consideration of complication risk and incorrect femoral neck anteversion.