Actual Hydrated Volume of Acellular Dermal Matrix in Prepectoral Breast Reconstruction.

Background/Objectives: Acellular dermal matrix (ADM) is increasingly used in prepectoral breast reconstruction, but operative planning still relies largely on label-reported size and thickness. In this study, we evaluated the actual post-hydration volumetric properties of commercially available ADMs and developed manufacturer-specific reference estimates for clinical use. Methods: In this single-center retrospective study, we analyzed 200 ADM sheets used in 173 patients between February 2023 and July 2025. Standardized 20 × 20 cm2 sheets from four manufacturers were hydrated, their true volumes were measured using the water displacement method, their measured hydrated areas were recorded, and their calculated thicknesses were derived from the hydrated volume divided by the measured hydrated area. Differences based on manufacturer and thickness group were analyzed, and manufacturer-specific reference estimates for other sizes were derived and compared with independent 18 × 18 cm2 validation data. Results: In all groups, the measured hydrated volume and measured hydrate area exceeded label-reported expectations. The measured hydrated volume and calculated thickness differed significantly according to the manufacturer and thickness group, and the interaction between these factors was also significant. The measured hydrated area varied less across thickness groups, although inter-manufacturer differences were observed within the shared 1.0-2.0 mm category. Validation with independent 18 × 18 cm2 data showed overall agreement with the derived reference estimates. Conclusions: Post-hydration ADM volumetric properties differ according to manufacturer and thickness group, largely because of differences in calculated thickness rather than area alone. The proposed manufacturer-specific reference table may serve as a practical aid for volumetric planning in prepectoral breast reconstruction.