Failure analysis and mechanical testing of Ti–6Al–4V modular revision hip stems
Bibliographic record
Abstract
Analysis of five modular titanium hip revision stems that failed in vivo was undertaken. The average time to failure was 4.0 ± 0.6 years with a range from 3.0 years to 4.9 years. The average age of the patients was 68.4 ± 7.6 years with a range of 61–81 years and the average mass was 88.0 ± 10.3 kg with a range of 71.7–98.9 kg. All five stems failed through fatigue just inside the taper junction between the stem and body. Microscopic analysis failed to detect any evidence of significant corrosion at the junction. Metallurgical analysis found that the material properties for the femoral stems were in agreement with typical values for Ti–6Al–4V. Mechanical testing revealed that fatigue failure would occur only with loads above 5000 N. This is far above any repetitive load that any of these stems would have undergone in vivo. Finite element analysis simulating a ‘worst case’ scenario demonstrated that a maximum tensile stress of 350 MPa would occur near the location of fracture seen on the retrieved stems. This stress is well below the fatigue limit of the titanium alloy. The exact location of the fracture in the mechanically tested components was affected by the assembly technique. It is suggested that the assembly technique could add considerable residual stress to the femoral stems causing them to fail well below the theoretical fatigue limit. Consideration for further investigation includes residual stresses within the implant secondary to assembly technique, and other unexplored factors that may lead to early fatigue failure.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".