Hemi-Versus Total Hip Arthroplasty in Femoral Neck Fractures? Predicting Failure on a 10-Year Data Analysis of the German Arthroplasty Registry (EPRD)

Abstract

Background/Objectives: The German Arthroplasty Registry (EPRD) recorded almost 100,000 femoral neck fractures between 2013 and 2023. The aim of this study was to identify survival rates and risk factors for failure in individuals with femoral neck fractures. Methods: A dataset of 97,410 cases from the EPRD was analyzed. We compared hemiarthroplasty (HA) and total hip arthroplasty (THA) using machine learning algorithms (MLAs) and statistical modeling approaches. For the MLA, the dataset was partitioned into training and test sets, with iterative feature selection and hyperparameter search. Predictive models were developed using XGBoost classifiers. Based on the feature importance, we performed LASSO regression to assess the odds ratios for key predictors of implant failure. Results: The failure rate was 3.7% for HAs and 5.6% for THAs, with a peak six weeks after surgery. LASSO regression revealed six risk factors for failure: non-cemented stem fixation (OR: 1.022, 95% CI: 1.019-1.026), treatment type (THA vs. HA; OR: 1.013, 95% CI: 1.010-1.016), time to discharge (OR: 1.006, 95% CI: 1.006-1.006), male sex (OR: 1.003, 95% CI: 1.000-1.005), age (OR: 0.999, 95% CI: 0.999-0.999), and day of surgery (weekday vs. weekend/holiday; OR: 1.004, 95% CI: 1.002-1.008). Conclusions: Longer hospital stays, male sex, and surgeries performed on weekends or holidays were associated with higher failure risks, while cemented fixation and hemiarthroplasty showed protective effects. Given that the overall failure rate was only 4.5%, even a 1-2% change in odds represents a very large clinical effect.

Keywords: EPRD; arthroplasty registry; cemented fixation; feature importance; femoral neck fracture; hemiarthroplasty; hip fracture; machine learning; total hip arthroplasty.

Figure 1

Study flowchart with data processing and analysis.

Figure 2

Kaplan–Meier plots with log-rank testing on arthroplasty survival and time to revision surgery (durability). (A) HA vs. THA, (B) cementless vs. cemented stem fixation, and (C) male vs. female patients were significant (log-rank, p < 0.001). (D) Surgery on weekdays vs. holidays/weekends showed no significant difference in survival analysis (log-rank, p = 0.146).

Figure 3

Relative failure distribution of the arthroplasties with focus on the first two years of observation (yellow line) and with focus on all cases (blue line). Failure occurs with a peak in the first 6 weeks.

Figure 4

MLA showed the feature importance of time to discharge as the most influential feature in predicting implant failure, followed by holiday and weekend, type of treatment, and number of cases per year. These features significantly contributed to the model’s ability to distinguish between failure and no-failure cases.

Figure 5

Predictors for failure of arthroplasty in femoral neck fractures are given as odds ratios with 95% confidence intervals. The highest risk for failure is a cementless stem fixation, followed by the treatment with THA compared to HA. Other predictors for failure were time to discharge, surgery on a weekend or holiday, and male sex (blue dotted line is an odd ratio of 1.0, green dots on the right are increased risk of failure, left reduced risk for failure). All included predictors are statistically significant.