Onlay Dural Graft: What It Is and How It Is Placed
An onlay dural graft is laid over a dural defect, overlapping the dura around it. What the term means, how it stays in place and which DESU grafts can be used.
An onlay dural graft is a dura substitute laid over a dural defect so that it overlaps the surrounding dura, rather than being sewn to the defect edge. Both DESU collagen membranes, DECOLL and DURASHEET, can be applied this way, at different CSF pressure levels. Both are made from pure Type I bovine collagen.
Key takeaways
- An onlay graft is laid on top of the dura, overlapping the defect edges, instead of being sewn edge to edge.
- Both DESU collagen membranes, DECOLL and DURASHEET, can be applied as an onlay at different CSF pressure levels.
- DURASHEET is also suturable and usable from either surface.
- Whether to use an onlay, and with how much overlap, is decided by the surgeon and the instructions for use.
Surgeons in training, OR nurses and buyers often meet the term on a product specification. For a comparison of the two closure methods, see onlay vs sutured duraplasty. The full range is on the dural grafts page.
What does “onlay” mean in dural repair?
“Onlay” describes where the graft sits. The dura is the tough outer membrane around the brain and spinal cord, and when part of it is missing or cannot be closed, a graft covers the gap. An onlay graft rests on the outer surface of the dura and extends past the defect on all sides, so its margins lie on healthy tissue.
The term is often used to mean “not sutured”, because an onlay graft is commonly placed without stitches. Strictly, though, it refers to position. A surgeon can place a graft as an onlay and still add a few tacking sutures.
How does an onlay differ from other graft placements?
| Placement | Where the graft sits | How it is held |
|---|---|---|
| Onlay | Over the dura, overlapping the defect edges | Contact with the surrounding tissue, with closure of the layers above |
| Underlay (inlay) | Beneath the dural edge | Tucked under the edge, with or without sutures |
| Sutured | Edge to edge with the dura | Stitches through graft and dura |
These words are not used identically in every department or paper, so if a specification or preference card says “inlay” or “onlay”, confirm what is meant.
How does an onlay graft stay in place?
A collagen sheet placed on a moist dural surface lies closely against it, and closing the overlying tissue layers helps keep it there. Some surgeons add a sealant or a few sutures according to their own protocol. Neither is part of the definition of an onlay.
An onlay graft is not the same thing as a watertight closure. What it can and cannot achieve is covered in watertight dural closure.
When might a surgeon choose an onlay?
The decision depends on the defect and the surgeon, and no single rule applies. Situations where a surgeon may choose an onlay include:
- Dura that is thin or friable, or that holds sutures poorly.
- Edges that are hard to reach with a needle.
- A defect where sutures alone would place the dura under tension.
Both membranes share the same uses: dural defects after spinal tumour surgery, dural defects after trauma, meningocele, myelomeningocele and surgical dural defects associated with lipoma. These are product uses, and the technique for each one remains the surgeon’s choice.
Which DESU grafts can be used as an onlay?
Both can. DECOLL and DURASHEET share their material, sizes and sterilisation, and both are applied as an onlay. DURASHEET adds properties that matter when a surgeon wants more than an onlay.
| Feature | DECOLL | DURASHEET |
|---|---|---|
| Onlay application | Yes | Yes |
| Suturable | — | Yes |
| Usable surface | See the IFU | Either surface |
| Pore structure | Impermeable | Impermeable |
| Other properties | Biodegradable | Biodegradable; high tensile strength; high absorption capacity |
| Sizes | 2.5 × 2.5, 5 × 5, 7.5 × 7.5, 10 × 10 cm | 2.5 × 2.5, 5 × 5, 7.5 × 7.5, 10 × 10 cm |
| Pre-processing | None | None |
| Sterilisation | Gamma | Gamma |
What does an onlay graft need to do?
With no sutures holding an onlay graft to the dural edge, attention moves to the sheet itself. Two features bear on this role:
- A barrier. The impermeable pore structure of both membranes forms a barrier at the repair site, intended to help control CSF leakage.
- A temporary structure. Both are collagen-based and biodegradable, a structure designed to support the healing process.
Being ready to use, with no pre-processing, also matters here: the team opens the membrane and passes it to the surgeon, without a preparation step.
How does an onlay affect the size to order?
Because an onlay extends beyond the defect, the graft has to be larger than the gap it covers. The size to open therefore depends on the defect and on the overlap the surgeon wants, which is set by the instructions for use and clinical judgement, not by a fixed rule. Both DESU membranes come in the four sizes above, from code DCL2525 or DRS2525 at the small end to DCL100100 or DRS100100 at the large end.
What should the OR team have ready for an onlay?
Onlay placement has few moving parts, so preparation is mainly a matter of confirming the surgeon’s plan before anything is opened:
- The product and size, from the preference card or a direct question, since the defect may need to be seen first.
- Whether a sealant or tacking sutures are planned. If sutures may be added, confirm the membrane, because DURASHEET is the suturable one.
- The label details needed for the implant record, including the code and lot.
Talk to a DESU product specialist
For the IFU or size and code details on DECOLL and DURASHEET, write to sales@desu.tr, use the contact page, or request a quote.
Frequently asked questions
Is an onlay graft the same as a sutureless graft?
Often in practice, but not by definition. Onlay describes where the graft sits, while sutureless describes how it is held. A graft placed as an onlay can still receive tacking sutures if the surgeon chooses.
Does DECOLL or DURASHEET need soaking before an onlay?
No. Both are supplied ready to use, with no pre-processing. Follow the instructions for use supplied with the product.
Can an onlay be used in spinal surgery?
Yes. Dural defects after spinal tumour surgery are among the uses of both DESU membranes, and both are applied as an onlay. The choice of technique in a given spinal case is the surgeon’s.
Does an onlay graft stay in the body permanently?
DECOLL and DURASHEET are biodegradable, so they are not intended as permanent implants.
Related standards
- ISO 22442 series: Medical devices utilizing animal tissues and their derivatives
- ISO 11137 series: Sterilization of health care products — Radiation
- ISO 10993 series: Biological evaluation of medical devices