Silicone vs Polysulfone Shunt Valves: Defit, Decurve, Depus

Silicone vs polysulfone shunt valve housings: what Defit, Decurve and Depus are made of, what changes with each, and how to describe them on a specification.

Silicone and polysulfone are different valve housing materials, and neither is better in itself. In DESU’s range, Defit has a flat-bottom silicone body, Decurve is made of polypropylene and silicone elastomer, and Depus has a polysulfone body with a ruby ball and titanium spring. Each material comes with a different valve design, so teams choose the whole valve, not the material alone.

Key takeaways

• Defit has a silicone body, Decurve is polypropylene and silicone elastomer, and Depus has a polysulfone body.
• Neither material is better in itself; each comes with a different valve design.
• The housing comes with a valve design: shape, size, mechanism, reservoir and pressure options differ by family.
• All three families use the same silicone ventricular and peritoneal catheters.

DESU shunt systems come in three families, and surgeons, theatre nurses and buyers often need to know what each housing is made of, what comes with it and how to describe it on a specification. Valve selection stays with the surgeon and the instructions for use.

What is a valve housing, and why do people ask about it?

The housing is the body of the valve: the outer part that holds the valve mechanism and lies beneath the scalp once implanted. People usually ask about its material for one of three reasons:

• A tender or product form has a material field to complete.
• A surgeon knows one valve well and wants to know how another is built.
• A radiology or biomedical team is checking what an implant is made of.

What is each DESU valve made of?

One detail matters when completing a form. Decurve is also referred to as a silicone shunt, but its full material description is polypropylene and silicone elastomer. “Silicone” is fair shorthand in conversation; on a specification, use the full wording.

How do silicone elastomer and polysulfone differ as materials?

Silicone elastomer is a flexible, rubber-like material with a long history in implantable devices. Polysulfone is a rigid thermoplastic, a hard engineering plastic used where a part has to hold its shape.

Those are descriptions of the two material classes, not measurements of a DESU valve. If an evaluation needs hardness, stiffness or durability data, our product specialists can tell you what is available.

What else changes with the housing?

The housing is tied to a valve design, so comparing materials alone misses most of the differences. The features below belong to each valve family, not to the housing material.

• Defit: a fixed-pressure, flat-bottom valve in three sizes, 35, 40 and 45 mm overall, with thicknesses of 4.5, 5.5 and 7 mm. It contains no metal.
• Decurve: a fixed-pressure, round burr-hole valve with a reservoir, in 23 mm paediatric and 28 mm adult nominal diameters. It contains no metal.
• Depus: a mechanical valve whose ruby ball and titanium spring mechanism opens automatically under positive ventricular pressure. It comes in low, medium and high fixed pressures and as adjustable valves, which are read and set with the Depus Adjustment Kit.

Two of those differences have their own articles: valve shape in flat-bottom vs burr-hole shunt valves, and imaging in metal-free shunt valves and imaging. Only Depus offers an adjustable setting, and only Defit and Decurve carry the “no metal” description. These are trade-offs for the surgeon to weigh.

Does the housing affect the antibiotic-impregnated options?

Antibiotic-impregnated versions exist in all three families, so the housing material does not decide whether the option is available. The antibiotic is impregnated into the material and released in a controlled manner over 28 days. What varies is which parts are impregnated:

• Defit: valves with an impregnated body, semi-antibiotic kits and full-antibiotic kits.
• Decurve: valves with an impregnated body, semi-antibiotic kits and full-antibiotic kits, in both sizes.
• Depus: fixed VP and LP kits with impregnated catheters. Adjustable Depus valves are also available with an antibiotic-impregnated body.

Impregnated catheters are orange and standard catheters white.

Do the catheters and kit contents change?

Not in a standard VP kit. All three families use the same catheters, so the material comparison stops at the valve. A VP kit contains the valve, a 23 cm ventricular catheter (1.3 mm inner, 2.5 mm outer diameter), a 120 cm peritoneal catheter (1.1 mm inner, 2.5 mm outer diameter), a stylet and a right-angled connector. Adjustable Depus kits add a silicone reservoir.

DESU’s ventricular and peritoneal catheters are silicone, so a Depus kit has a polysulfone valve and silicone catheters. All shunt systems are single-use and sterilised by ethylene oxide, and an antisiphon device is an option on all three families.

How should a specification describe the housing?

A specification works best when it records the exact material wording and leaves the comparison out:

• Name the family and the full material: silicone body for Defit, polypropylene and silicone elastomer for Decurve, polysulfone body for Depus.
• Add the features the surgeon actually chose: valve shape, size, pressure, reservoir and, for Depus, fixed or adjustable.
• Keep valve material and catheter material on separate lines.
• Avoid writing a material as a requirement unless the department has a reason for it, because it can rule out a valve nobody meant to exclude.
• Use the order code where possible. DFS-M is a medium-pressure Defit Small valve, DCP-M a medium-pressure paediatric Decurve valve and DP-M a medium-pressure Depus valve.

How is the choice usually made?

The housing is rarely the starting point. The surgeon works through the questions below, and the valve family, and with it the housing, follows from the answers.

• Fixed or adjustable: is the option of changing the pressure after implantation wanted?
• Route: ventriculoperitoneal or lumboperitoneal?
• Position: at the burr hole, or separate from it on the skull?
• Patient: which valve size suits the anatomy?
• Reservoir: built in, optional or not needed?
• Imaging: what does the follow-up plan involve, and what do the instructions for use say?

A department may stock more than one family for this reason. That reflects technique and case mix, not a verdict on silicone or polysulfone.

Talk to a DESU product specialist

If you need to confirm the materials of a Defit, Decurve or Depus valve for a specification or tender, DESU’s product specialists can help. Write to sales@desu.tr, use the contact page, or request a quote.

Frequently asked questions

Is the Decurve valve pure silicone?

No. Decurve is polypropylene and silicone elastomer, although it is also referred to as a silicone shunt. Use the fuller description on specifications and tender forms.

Does a polysulfone Depus valve contain metal?

Yes. The polysulfone body holds a ruby ball and titanium spring mechanism, so Depus does not carry the “no metal” description used for Defit and Decurve. Imaging conditions for a Depus valve are set out in its instructions for use.

Is every adjustable DESU valve polysulfone?

Yes. In DESU’s range the adjustable valves are Depus valves, which have a polysulfone body. Defit and Decurve are offered in fixed low, medium and high pressures only.

Related standards

• ISO 7197: Neurosurgical implants — Sterile, single-use hydrocephalus shunts and components
• ISO 11135: Sterilization of health-care products — Ethylene oxide
• ISO 13485: Medical devices — Quality management systems