What Embedding-Based Guideline-Literature Drift Measures (and What It Doesn't): A Proof-of-Concept and Mechanistic Dissection of TIDE in Orthopedic Surgery

Purpose: We introduce the Temporal Index of Divergent Evidence (TIDE), a metric that evaluates how the topic center of gravity of a corresponding corpus of literature aligns with, or shifts relative to, a recommendation's semantics over time. Methods: TIDE computes annual mean cosine similarity using MedCPT embedding vectors between a recommendation and corresponding PubMed records binned by year (2000-2024), testing for monotonic temporal trend (Kendall {tau}). Three recommendations with expected divergent, stable, and convergent trajectories were examined: two-stage exchange for periprosthetic joint infection (PJI), emergent fasciotomy for acute compartment syndrome (ACS), and non-operative management of distal radius fractures (DRF) in adults [≥] 65 years. The signal was characterized by an additive per-token attribution, an isolated vs. in-context analysis, and an adversarial minimal-pair test. Results: PJI diverged ({tau} = -0.84, year-shuffle p = 0.001), DRF converged ({tau} = +0.42, p = 0.005), and ACS showed no detectable trend ({tau} = -0.07, p = 0.66). The two significant directions (PJI, DRF) held under matched input [CLS] pooling, while ACS remained near zero. Publication volume baselines did not distinguish the three trajectories (publication count was universally positive, {tau} = +0.77 to +0.97). A reversed-meaning minimal-pair control showed little cosine sensitivity to reversal. Paper-level TF-IDF recovered the qualitative three-case pattern. Conclusion: Embedding-based drift analysis is a proof-of-concept candidate pre-triage signal that tracks topical alignment, not evidentiary direction; superiority over TF-IDF remains unproven. The present study is hypothesis-generating, showing potential use of embedding representations as an analytical unit rather than simply for retrieval.