Filing is concentrated at the top: the top five assignees together hold 226 of the 302 records in scope, or 74.8% of the field, and the single leading assignee holds 100 records on its own. The drop-off after that is steep — fifth place holds 20 records and tenth place holds 7 — so this is a field shaped by one dominant filer plus a handful of secondary players, not an evenly distributed one. Anyone assessing freedom to operate should check the leader's claim scope first, since it covers the largest single block of prior art.

Filing peaked in 2020 at 15 records and has eased since, with 2021's 6 records falling to 2024's 2 — a 67% drop over that three-year span. However, 2025 and 2026 figures in this dataset are still incomplete because patent publication typically lags filing by around 18 months, so the most recent years understate real activity. The honest read is that filing has cooled from its 2020 peak, not that the technology area is winding down.

This dataset is built around records that explicitly address modality transition alongside ethylene oxide process detail — cycle parameters, residual limits, emission control, aeration time, and facility permitting. The technology composition shows heavy overlap with A61F implants (29.5% of records) and A61K medicinal preparations (18.9%), meaning alternative-modality claims are usually tied to a specific device or formulation rather than filed as standalone process patents. Practitioners should expect alternative-modality art to surface inside device-specific filings, not a separate clean category.

The clearer openings sit in the operational and validation layers rather than the core sterilization chemistry: facility emission-control retrofit methods, modality-transition validation protocols, and residual ethylene oxide degassing sensors show thinner direct coverage relative to the dense core cycle-parameter claims. These areas tend to require regulatory or facility-level detail that fewer of the dominant filers have bothered to claim narrowly. A first claim in these branches would likely need to tie a specific sensor, protocol step, or emission threshold to a named regulatory trigger to clear the existing art.

Citation counts in this corpus skew toward older, broadly drafted filings — the most-cited records here relate to enzyme-based coatings and molecular healing methods, filed years before the more device-specific sterilization sensor patents that followed. That is a structural bias of citation counting within any searched corpus, not evidence that those older filings are more commercially relevant today. Use citation rank as a signal of historical influence, and cross-check against recent filing activity and assignee concentration before weighting a patent as strategically important.