REDUCED FRACTURES AND STEM SUBSIDENCE AT SIX MONTHS WITH COLLARED STEMS IN DIRECT ANTERIOR CEMENTLESS TOTAL HIP ARTHROPLASTY
Bibliographic record
Abstract
Many femur fractures in total hip arthroplasty (THA) occur during advancement of the final stem, especially during a direct anterior approach (DAA). Calcar collars are a re-emerging trend among cementless stem designs which may reduce fracture risk by both preventing subsidence and acting as an intraoperative cue for sufficient stem advancement. We hypothesize that collared femoral stems have lower risk of intraoperative and post-op periprosthetic fracture and stem subsidence compared to collarless designs in DAA THA at 6 months. A retrospective review of 348 DAA THAs on a Hana table performed from 2017–2020 by a single surgeon, fellowship trained in arthroplasty, was done. Three cementless stems with similar broach systems were studied: Zimmer ML Taper, Avenir & the Avenir-Complete with a collar. Only patients with Dorr A or B femurs received cementless THA. Incidence of intraoperative fractures and post-operative Vancouver AL/B fractures within 6 months were recorded. Radiographic stem subsidence was measured and compared at 6-months by the attending surgeon and 2 independent observers. Routine 3-dimensional post-operative imaging to quantify subsidence was not feasible at our institution. Fisher-Exact test was used to compare outcomes between the collared vs non-collared designs with p 3mm was deemed clinically significant based on prior studies for similar broached stems. Both groups were comparable in sex, smoking history, diabetes, Dorr type and BMI. Patients with the collared stem had significantly fewer femur fractures compared to collarless stem designs (0/99 vs. 11/249) (p=0.043). 3 patients had intra-operative calcar cracks requiring cerclage and 8 required revision post-op. Radiographic subsidence >3 mm was also significantly lower in the collared stem group (p < 0.001) at 6 months. No statistically significant differences were observed in infection (p=0.55), hematoma formation (p=0.10), or wound complications (p=0.47). The use of collared cementless femoral stems in DAA THA resulted in significant reduction in periprosthetic femur fractures and subsidence compared to collarless stems. This was likely due to the collar acting as an intraoperative and post-operative calcar stop against over-advancement in the canal. There were no cases of early loosening with any of the stems. A prospective multi-surgeon study comparing collared and collarless versions of the Avenir-complete stem would yield stronger data. Subsidence would be more reliably measured with 3D imaging and radiostereometry. Implementing collared femoral stem designs may lead to further cost-savings and lower fracture rate in patients undergoing DAA THA.
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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) | 0.000 | 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".