Hip Resurfacing Arthroplasty Is Associated with Lower Metal Ion Levels and Revision Risk Compared with Large-Head Metal-on-Metal Total Hip Arthroplasty
Bibliographic record
Abstract
BACKGROUND: Large-diameter head total hip arthroplasty (LDH-THA) emerged in the late 1990s as a stemmed alternative to hip resurfacing arthroplasty (HRA). Both procedures use metal-on-metal (MoM) bearings to permit larger heads, lower dislocation risk, and optimize function in younger, active patients. While concerns over metal ion release and adverse local tissue reactions curtailed MoM use, long-term follow-up remains critical for the substantial population with these devices in situ. This review compares LDH-THA and HRA in clinical outcomes, metal ion levels, and revision rates to guide long-term management and future implant design. METHODS: PubMed, Embase, and Scopus were searched for studies reporting patient-reported outcomes, metal ion levels, or revision rates for both LDH-THA and HRA. The risk of bias was assessed using the Methodological Index for Non-Randomized Studies score. Random-effects meta-analysis evaluated revision risk; cobalt and chromium levels; University of California, Los Angeles (UCLA) activity; Harris-Hip Scores (HHS); Oxford Hip Scores (OHS); and Western Ontario and McMaster Universities Osteoarthritis Index. RESULTS: Of 221 studies, 21 met inclusion criteria, including 5,545 LDH-THAs and 3,197 HRAs. The unweighted pooled revision rate was 16% for THA and 7.8% for HRA. Meta-analysis showed higher cobalt (standardized mean difference [SMD] 1.07) and chromium (SMD 0.53) levels in THA. Revision risk (odds ratio 1.75), UCLA (-0.44), and HHS (-0.32) favored HRA, though not significantly. CONCLUSION: Although the usage of large-head MoM THA is largely historic, our findings suggest that MoM hip resurfacing arthroplasty has a more favorable outcomes profile with reduced systemic metal ion exposure, reinforcing its role in younger, active patients, where conventional or large-head THA may fall short. LEVEL OF EVIDENCE: Level III, systematic review of Level I, II, and III studies. See Instructions for Authors for a complete description of levels of evidence.
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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 | 0.010 | 0.035 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.004 | 0.011 |
| Bibliometrics | 0.004 | 0.006 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.001 |
| 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".