Comparative Results between Conversion to Total Hip Arthroplasty Secondary to Failed Osteosynthesis versus Total Hip Arthroplasty after Femoral Neck Fracture

Purpose Conversion to total hip arthroplasty (cTHA) after failed osteosynthesis has been associated with higher complication rates than elective THA, yet comparative evidence in femoral neck fractures (FNF) remains limited. This study compared length of stay (LOS), complication rates, and 90-day unplanned readmissions between patients undergoing cTHA and those treated with primary THA for FNF (pTHA). Methods A retrospective cohort study was performed at a tertiary center between 2015 and 2022. Patients undergoing cTHA after failed osteosynthesis or hybrid pTHA for displaced FNFs were included, with a minimum follow-up of one year. Demographic variables (age, sex, BMI, ASA score, Charlson comorbidity index) and postoperative outcomes were analyzed. Results A total of 106 patients were included: 75 pTHA and 31 cTHA. Mean follow-up was 36.2 months (4–85). Operative time was significantly longer in the cTHA group (94.9 vs. 74.9 minutes, p = 0.002). LOS was similar between groups (6.9 vs. 5.48 days, p = 0.12). Ninety-day complication rates did not differ significantly (32% pTHA vs. 16.1% cTHA, p = 0.14). Unplanned readmissions were also comparable (18.6% vs. 16.1%, p = 0.75). Conclusion Despite longer operative times, cTHA demonstrated similar LOS, complication rates, and 90-day unplanned readmissions compared to pTHA for FNF. These findings suggest that, when appropriately indicated and performed in experienced centers, cTHA is a safe salvage option following failed osteosynthesis. Nevertheless, meticulous preoperative planning remains essential due to the increased complexity of conversion procedures.