Hip arthroplasty for acute femoral neck fracture: Hemiarthroplasty, dual mobility, or conventional total hip arthroplasty? A comparative analysis of 37,169 hip arthroplasties from the Swiss National Joint Registry

BACKGROUND: The optimal choice of the type of hip arthroplasty for managing acute femoral neck fractures (FNF) remains controversial, particularly when deciding between total hip arthroplasty (THA) and hemiarthroplasty (HA). Dual mobility cups (DM) have demonstrated efficacy in preventing instability, which is a potential concern with conventional THA. This study aimed to compare the outcomes of HA, DM, and conventional THA for managing FNF using data from a nationwide cohort collected through the Swiss National Joint Registry (SIRIS). HYPOTHESIS: Hemiarthroplasty has lower revision rates in older patients, while THA demonstrates lower revision rates in younger patients. PATIENTS AND METHODS: Between 2012 and 2022, 37,169 patients who underwent hip arthroplasty for FNF in Switzerland were prospectively and systematically included in the SIRIS national registry. This cohort included 22,053 HA, 3,263 DM THA, and 11,853 conventional THA procedures. The study compared revision rates and implant survivorship for both septic and aseptic failures among these groups. Hazard ratios (HR) for revisions were calculated to compare HA, DM, and conventional THA, with subgroup analyses performed after adjusting for age, gender, BMI, and ASA scores. RESULTS: At the 10-year follow-up, the cumulative revision rates were 7.8% [6.4-9.4] for HA, 8.1% [7.6-10] for DM THA and 8.7% [7.7-9.9] for conventional THA. HA showed a trend toward a lower revision risk compared to DM and conventional THA (HR = 0.86 [95% CI: 0.72-1.02]), though this did not reach statistical significance. However, in patients <65 years, HA had a high 10-year revision rate of 20.7% [13.5-31.1], with 56.1% of these revisions involving conversion to THA. In addition, HA with cementless femoral stems had a significantly higher revision rate due to femoral periprosthetic fractures compared to cemented stems (HR = 1.81 [95% CI: 1.39-2.38]). Moreover, HA performed through a posterior approach had significantly higher revision rates due to dislocations compared to anterior approaches (HR = 1.64 [95% CI: 1.27-2.11]). DISCUSSION: When managing acute FNF with hip arthroplasty, there was no significant difference in revision rates or survivorship between HA, DM THA, and conventional THA at 10 years. However, for patients under 65 years, HA demonstrated a 20% revision rate over 10 years, with over half of these revisions involving conversion to THA. Based on these results, THA is recommended for younger patients, especially when life expectancy exceeds 10 years. For older patients, HA remains a viable option, provided certain technical considerations are followed i.e. the use of cemented femoral stems to reduce the risk of femoral periprosthetic fractures and the anterior approaches to minimize the risk of dislocation. These findings underlined the importance of tailoring arthroplasty choices to individual patient characteristics, including age, life expectancy, and surgical technique. LEVEL OF EVIDENCE: III.