A high offset stem design does not increase stem migration under full weight bearing in cementless total hip arthroplasty: a model-based RSA study
Bibliographic record
Abstract
BACKGROUND: High-offset stems in cementless primary total hip arthroplasty (THA) have been potentially associated with early aseptic femoral loosening. This study aimed to evaluate the primary and secondary stability of a cementless high-offset femoral component under full weight-bearing conditions using model-based RSA, comparing it with a standard offset stem in patients undergoing THA. METHODS: In this prospective, observational, single-center study, 42 patients with end-stage hip osteoarthritis underwent cementless primary THA using either a standard (SL-PLUS Standard) or a high-offset (SL-PLUS Lateral) cementless stem. Radiostereometric analysis (RSA) was employed to monitor stem migration at six weeks and three, six, twelve, and twenty-four months. Clinical outcomes were assessed using the modified Harris Hip Score (HHS) and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). RESULTS: There were no significant differences in mean stem subsidence between the groups at any follow-up interval, indicating comparable primary and secondary stability. After minimal initial subsidence (SL-PLUS Standard: up to -0.54 mm; SL-PLUS Lateral: up to -0.73 mm), no further progressive migration was observed. A significant difference in stem anteversion was noted between the groups at six months (P = 0.021) and two years (P = 0.001). The SL-PLUS Lateral group had significantly better WOMAC scores at the two-year follow-up (P = 0.027). CONCLUSIONS: This RSA study demonstrated similar migration patterns for the high-offset and standard-offset cementless stems within the first two years after operation. Both groups exhibited initial subsidence followed by high secondary stability. Based on the results of this study, the SL-PLUS Lateral is a safe alternative for patients with high femoral offset undergoing cementless THA.
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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 | 0.001 | 0.002 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.001 |
| 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) | 0.001 | 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 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".