Conversion of Failed Hemiarthroplasty to Total Hip Arthroplasty Remains High Risk for Subsequent Complications

Background: Few studies have described the outcomes following conversion of failed hemiarthroplasties to total hip arthroplasty (THA) and the impact of mortality when estimating implant survivorship. The aims of this study were to evaluate the following: (1) the risks and predictors of complications, dislocations, reoperations, and revisions and (2) the extent of competing risk of death when evaluating outcomes in patients converted from hemiarthroplasty to THA. Methods: The study comprised 389 patients treated with conversion THA following hemiarthroplasty for femoral neck fractures between 1985 and 2014. Revision rates were calculated using both the Kaplan-Meier method and cumulative incidence accounting for death as a competing risk. Risk factors were evaluated using Cox regression models. Results: During an average 9.3 years of follow-up, there were 122 complications, 34 dislocations, 69 reoperations, and 51 revisions. Conversion for periprosthetic fractures was associated with a higher risk of reoperations (hazard ratio 4.30, 95% confidence interval 1.94-9.52). Increasing age was a risk factor for reoperations (hazard ratio 1.32, 95% confidence interval 1.10-1.59). No decrease in the rate of complications, dislocations, reoperations, or revisions was observed over the entire 30 years of the study either when evaluating year of surgery as a continuous variable or when comparing specific calendar year intervals (1985-1989, 1990-1999, 2000-2009, 2010-2014) (P >.05). Compared to the cumulative incidence accounting for the competing risk of death, the Kaplan-Meier method overestimated the risk of revision by 7% at 15 years and 10% at 20 years. Conclusion: Conversion from hemiarthroplasty to THA remains at high risk for subsequent complications. The cumulative incidence estimate provides a more accurate estimate of revision risk.