EP259 The impact of periacetabular osteotomy on peak contact area and stresses within the hip
Bibliographic record
Abstract
Abstract Acetabular dysplasia results in a shallow acetabulum, which reduces femoral head contact, leading to overloaded cartilage and high risk of early osteoarthritis. Periacetabular osteotomy (PAO) is a surgical procedure used to correct acetabular alignment before cartilage degeneration occurs. There is limited data on how PAO affects joint contact pressures. This study aims to analyze the joint mechanics in dysplastic hips before and after PAO during tasks such as squatting and walking. CT scans were taken before and after PAO for six participants (2 males, 4 females, ages 18-43) with acetabular dysplasia. They performed squatting and walking tasks in a lab pre- and post-surgery. An optoelectronic camera system recorded pelvis and limb displacement, while force platforms measured ground reaction forces. Joint angles and reaction forces were calculated from this data using personalized musculoskeletal models in OpenSim. Joint contact areas and pressures were simulated using a discrete element model with patient-specific bone meshes and cartilage surfaces generated based on Nishii’s method. Peaks in contact area, maximal pressure and mean pressures were compared with the Wilcoxon test. Walking results showed a significant increase in peak joint contact area post-surgery (6.5 ± 1.5 cm2 to 8.1 ± 2.4 cm2, p = 0.03), though no significant changes were found in peak max pressure (17.2 ± 3 MPa to 15.5 ± 3.9.4 MPa, p = 0.56) and peak mean pressure (7.0 ± 0.9 MPa to 5.2 ± 1.5 MPa, p = 0.09). There was no significant change in peak contact area (6.3 ± 1.7 cm2 to 7.0 ± 1.6 cm2, p = 0.31) nor in peak max and mean pressures (13.9 ± 5.6 MPa to 13.6 ± 2.6 MPa; 5.7 ± 2.8 MPa to 4.6 ± 0.8 MPa) for the squat. PAO improved joint contact area in dysplastic hips during walking, although this did not lead to significant changes in peak pressures. In high-flexion activities like squatting, lateral acetabular repositioning may not fully offset the loss of posterior coverage. Although all metrics’ means moved in the desired direction, the benefits of PAO to reduce peak stresses are not apparent in this small cohort.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 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) | 0.004 | 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 source (direct Gemma or distilled Codex), 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".