Risk of Periprosthetic Femoral Neck Fracture After Hip Resurfacing Arthroplasty: Valgus Compared with Anatomic Alignment
Bibliographic record
Abstract
BACKGROUND: Early clinical results of hip resurfacing arthroplasty have led to the recommendation to achieve a neck-shaft angle of 140 degrees when inserting the femoral component. In addition, the idea of adhering to an absolute angle when inserting instrumentation in hips with excessive anatomic varus or valgus neck-shaft angles has raised concern. A biomechanical analysis was completed in order to determine if the achieved valgus orientation of the femoral component reduced the risk of periprosthetic fracture. METHODS: Twenty fresh-frozen cadaveric femora were blindly assigned to be implanted with a neutral or valgus-oriented hip-resurfacing femoral component. Bone mineral density scans were acquired for all femora. All specimens were loaded axially to failure at a rate of 0.21 mm per second. Radiographs of the specimens were measured in order to determine the relative valgus orientation of the femoral components and the change in offset. RESULTS: There was a significant increase in the ultimate failure load for the valgus-oriented components. While the bone density scans revealed that the bone mineral densities measured in the neutral and valgus-oriented femoral components were almost identical, the ultimate failure load was found to be significantly increased for the valgus-oriented components (6955 N) compared with the neutral-oriented components (5254 N). For the valgus-oriented femoral components, two had failure at the subcapital level, seven had vertical shear fractures, and one had an anterior shear fracture. For the neutral-oriented components, five subcapital fractures and five vertical shear failures were observed. CONCLUSIONS: The study suggests that a valgus orientation decreases the risk of periprosthetic femoral neck fracture following hip resurfacing. It also brings into question the use of an absolute angle for all patients. Obtaining the maximum possible valgus angle, while avoiding notching, may in fact provide the optimum protection from periprosthetic femoral neck fractures.
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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 | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| 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) | 0.000 | 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".