The Effectiveness of Alpha‐2‐Macroglobulin Injections for Osteoarthritis of the Knee
Bibliographic record
Abstract
BACKGROUND: Intra-articular (IA) injections of plateletrich plasma (PRP) have been increasingly used in the nonoperative treatment of knee osteoarthritis (OA) but have considerable heterogeneity in both formulation and clinical results. Alpha-2-macroglobulin (A2M) is a large plasma protein found in PRP that inhibits cartilage-degrading enzymes and could be an efficacious OA treatment independently. The purpose of this study was to compare the short-term clinical efficacy of IA injection of A2M-rich PRP concentrate to conventionally prepared PRP and corticosteroids in the management of symptomatic knee OA. METHODS: This double-blinded, randomized, controlled clinical trial was conducted at a single medical center with enrollment from June 2018 to May 2019. Subjects with symptomatic Kellgren-Lawrence (KL) grade 2 or 3 knee OA were randomized to IA injection with A2M, PRP, or methylprednisolone (MP) and followed for 12 weeks post-injection. Knee pain and function were assessed at pre-treatment baseline and at 6-week and 12-week followup with patient-reported outcome (PRO) surveys including the visual analog scale (VAS) for pain, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), Knee Injury and Osteoarthritis Outcome Score (KOOS), Lysholm score, and Tegner score. RESULTS: Seventy-five subjects were enrolled in the trial, of whom 68 (90.7%) completed the 12-week follow-up. The majority of subjects (73%) were female with a mean age of 59 years (range: 37 to 75 years). There were no significant differences in age (p = 0.30), sex (p = 0.44), or KL grade (p = 0.73) between treatment groups. By 12 weeks postinjection, the A2M group showed significant improvement in VAS, WOMAC, KOOS, and Tegner (p < 0.05), the PRP group showed no significant improvement in any PROs (p > 0.05), and the MP group showed significant improvement in Lysholm only (p = 0.01). However, the changes in PRO scores between baseline and 12-week follow-up did not significantly differ between the three groups (p > 0.05). CONCLUSIONS: Alpha-2-macroglobulin IA injection shows comparable efficacy to PRP and corticosteroids in the treatment of mild-to-moderate knee OA. Alpha-2-macroglobulin treatment resulted in modest improvement in knee pain and function at 6-week follow-up, albeit inconsistently across PRO measures and to a similar degree as PRP and corticosteroids. Given its non-superior short-term efficacy compared to established IA injections, as well as its increased cost of preparation, A2M may not be a justifiable option for routine treatment of knee OA.
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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 | 0.002 | 0.002 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.001 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.001 |
| Insufficient payload (model declined to judge) | 0.002 | 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".