A Prospective Case Series Examining the Use of a Large-Head Metal-on-Metal Total Hip System
Bibliographic record
Abstract
To minimize wear-related failures and the risk of post-operative instability, large-head metal-on-metal (MoM) total hip replacement (THR) systems were introduced. However, concerns have been raised following high early failure rates of these implants. The purpose of the present study was to report the early clinical results of our center’s experience using a large-head MoM THR system. From October 2005 to May 2010, 88 patients (53 males, 35 females- 89 hips) with a mean age of 59.7 ± 9.8 yr (range: 20 to 79) had the CONSERVE® Total Hip with BFH® (Big Femoral Head, diameter 36–54 mm) MoM and a modular femoral system (Profemur™) implanted by four surgeons. The mean body mass index was 29.5 ± 6.2 (range: 21.2 to 44.8). Post-operative follow-up consisted of physical examination, standard radiographs, and three patient-reported outcomes: Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), modified Harris Hip Score (HHS), and University of California at Los Angeles (UCLA) Physical Activity Scale. At mean follow-up of 30 months (range: 24 to 72), all outcomes from the whole cohort showed improvement (p < 0.001). Mean WOMAC scores increased from 49.1 (pre-surgery) to 83.6 (follow-up) (pain), 44.5 to 73.2 (stiffness), 47.4 to 81.7 (function), and 47.5 to 81.4 (total). Mean modified HHS and UCLA activity scores improved from 54.0 to 82.4 and from 4.7 to 6.4, respectively. Nevertheless, nine cases required revision (mean = 31.9 months, range: 11 to 48) because of aseptic cup loosening (n = 6) or pseudotumor (n = 3). In the whole cohort, no patient had lucencies greater than 1.5 mm in three or more femoral zones. Three patients showed a radiographic lucency greater than 1 mm in one acetabular zone and one showed signs of cup migration greater than 5 mm and tilting greater than 5°. The mean cup inclination did not differ between patients requiring revision and those who retained their implant (43.3° versus 43.5°; p = 0.91). Because a high revision rate of a large-head MoM THR was observed due to poor acetabular component fixation and adverse tissue reactions, use of this implant should be restricted to conversion of a failed resurfacing arthroplasty with a well-ingrown cup and in the absence of an adverse local tissue reaction.
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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 | 0.005 |
| Meta-epidemiology (narrow) | 0.001 | 0.001 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.002 | 0.002 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.002 | 0.002 |
| Insufficient payload (model declined to judge) | 0.004 | 0.002 |
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".