Dehydrated vs cryopreserved amniotic grafts

Why preservation matters

Amniotic membrane is a perishable biologic. To distribute it as an allograft under FDA HCT/P regulations ^[1], the tissue must be preserved in a way that maintains structural integrity and (depending on product positioning) some of its biological activity. The two dominant approaches in U.S. wound care are dehydration and cryopreservation.

Dehydrated amniotic membrane (dHACM, dHAM)

Dehydration removes most of the water from the membrane after donor screening and processing. Dehydrated products are typically shipped and stored at ambient temperature, with shelf lives commonly in the 3–5 year range per the manufacturer''s instructions for use. Clinical handling is straightforward: the sheet is rehydrated briefly at the point of care, sized to the wound, and applied with a non-adherent secondary dressing.

Reported composition includes extracellular matrix proteins and a range of growth factors retained after the dehydration process. The exact composition depends on the manufacturer''s proprietary process and on lot variability; rely on the package insert for current product-specific data ^[2].

Cryopreserved amniotic membrane (CAM)

Cryopreservation freezes the tissue, often with cryoprotectants, and the product is shipped and stored frozen (commonly –65 °C to –80 °C). Some cryopreserved products are positioned as retaining viable cells in addition to the matrix and growth factors; the regulatory status of viable-cell products has been an area of FDA focus and may affect a given product''s 361/351 classification ^[1].

Cryopreserved products require cold-chain logistics, dedicated freezer storage at the clinic, and a thaw protocol before use. Shelf life on-site is typically shorter than dehydrated products once removed from the freezer.

Clinical and operational comparison

| Dimension | Dehydrated | Cryopreserved | | --- | --- | --- | | Storage | Ambient | Frozen (often –80 °C) | | Shelf life | Typically 3–5 years | Typically 1–2 years frozen | | Handling at point of care | Rehydrate, size, apply | Thaw, size, apply | | Clinic infrastructure | Minimal | Freezer + protocol | | Reported composition | ECM + growth factors | ECM + growth factors (some products: viable cells) |

This is a generalized comparison. Always consult the specific product''s instructions for use for storage, handling, and composition claims ^[2].

Evidence considerations

Direct head-to-head randomized trials comparing dehydrated vs cryopreserved amniotic allografts in the same wound type are limited. Most published RCTs compare a single product against standard of care, not against another preservation format. Indirect comparisons across trials are confounded by differences in study population, protocol, and outcome definitions. Systematic reviews note that evidence for "amniotic membrane allograft" as a class should not be assumed to apply equally to every product within the class ^[3].

How clinicians typically choose

Selection in practice is driven by a combination of clinical evidence for the specific product in the specific wound type, the practice''s existing storage and handling infrastructure, the LCD coverage of the product in the practice''s MAC jurisdiction, and supply reliability. Many wound-care practices stock a primary product and a secondary option to manage supply or coverage variability.

Related resources

• Amniotic membrane allograft for diabetic foot ulcers
• Graft size selection and wound measurement
• Amniotic allograft Q-codes: a clinician reference