Depus Fixed-Pressure Valve: Ruby Ball and Titanium Spring

How the fixed-pressure Depus shunt valve works: a polysulfone body, a ruby ball and a titanium spring that respond to positive ventricular pressure.

The fixed-pressure Depus valve is a mechanical shunt valve with a polysulfone body. Inside, a ruby ball and a titanium spring form the mechanism. Positive ventricular pressure activates it, and CSF passes when that pressure is high enough for the valve's setting. Low, medium and high models give three fixed settings within DESU's shunt systems.

Key takeaways

• The Depus valve is a mechanical shunt valve with a polysulfone body, activated by positive ventricular pressure.
• A ruby ball and a titanium spring form a hydrodynamic leverage mechanism.
• Fixed-pressure models come in low, medium and high settings: DP-L, DP-M and DP-H.
• A fixed valve does not change after implantation. Antisiphon, reservoir and adjustable options are separate choices.

What does a shunt valve have to do?

A hydrocephalus shunt moves cerebrospinal fluid (CSF) from the ventricles to another part of the body where it can be absorbed. The valve sits on that path, between the proximal and distal catheters, and it decides when fluid may pass.

It has a narrow job with two ways to fail. If it opens too easily, the shunt can drain too much. If it resists too much, it can drain too little. A passive mechanical valve has to manage this with no power source, no sensor and no electronics, for as long as it stays implanted.

What is inside the Depus valve?

Three parts define the Depus valve:

• A polysulfone body, the rigid housing of the valve.
• A ruby ball, one of the two components of the mechanism.
• A titanium spring, the other component of the mechanism.

The valve works mechanically and responds to positive ventricular pressure, with the ruby ball and titanium spring acting as the components of a hydrodynamic leverage mechanism.

How does a ball-and-spring valve open and close?

In a ball-and-spring valve, the spring holds the ball against the flow path. Fluid pressure on the inlet side pushes the other way. The sequence is simple:

• At rest, the spring force keeps the ball seated and the path closed.
• When pressure on the inlet side rises enough to overcome that force, the ball moves and CSF flows through.
• As pressure falls, the spring returns the ball and the path closes again.

Two points follow from this. A valve like this responds to a pressure difference across it, not to a volume of fluid, so it has no target for how much CSF to drain in a day. And the setting comes from the mechanism itself: nobody has to operate the Depus valve, which opens automatically under positive ventricular pressure.

What are the properties of ruby, titanium and polysulfone?

Ruby is a crystalline form of aluminium oxide. It is very hard and can be finished to a smooth, accurate sphere, which is why ruby has a long history as a bearing material in precision instruments such as mechanical watches. Those are useful properties for a small part that has to move and reseat in a mechanism.

Titanium is strong for its weight, resists corrosion and is widely used in implanted medical devices. Polysulfone is a rigid thermoplastic, and a rigid housing keeps the parts of a mechanism in a stable relationship to each other. That differs from the silicone bodies of the Defit and Decurve valves.

What do low, medium and high pressure mean on a Depus valve?

Fixed-pressure Depus valves are offered in three settings, and the setting appears in the product code:

Teams that need numeric opening pressures should work from the instructions for use. Choosing a setting for a patient is a clinical decision for the surgeon.

The word fixed means the setting belongs to the model. To work at a different pressure, the patient needs a different valve. How that compares with an adjustable valve is covered in fixed-pressure vs adjustable shunt valves.

What does a fixed-pressure valve not do?

Because the mechanism responds to the pressure difference across it, posture can matter. When a patient stands up, the column of fluid in the distal catheter can add a siphon effect that the valve setting alone does not account for. DESU's antisiphon device is an option for this, added to certain Depus configurations, and kits that include it have codes ending in “-ASD”. The article on how the antisiphon device counters the siphon effect explains the mechanism.

Other functions sit outside the valve as well. A reservoir can be added to Depus systems as an option. Pressure changes after implantation are the role of the adjustable Depus valves, which are read and set with the Depus Adjustment Kit. That kit is designed for use with adjustable Depus valves.

What should a team confirm before using a Depus valve?

• The setting on the label matches the surgeon's order: L, M or H in the code.
• Whether the order is for the valve alone or a VP or LP kit.
• Whether the kit should include the antisiphon device, shown by the “-ASD” suffix.
• Imaging questions. Defit and Decurve contain no metal, while Depus has a titanium spring, so follow the instructions for use.

Depus valves carry the CE mark, are made under ISO 13485 and are sterilised with EO. The valve size is suitable for paediatric and adult patients.

Talk to a DESU product specialist

For the instructions for use, product codes or help matching a Depus configuration to your order, write to sales@desu.tr, use the contact page or request a quote.

Frequently asked questions

Can the setting of a fixed-pressure Depus valve be changed after implantation?

No. The low, medium and high models are fixed. Adjustable Depus valves are a separate product line, and the Depus Adjustment Kit is designed for use with those.

Is the Depus valve metal-free?

No. It has a titanium spring. DESU's metal-free valves are Defit and Decurve.

Is the Depus valve also used in lumboperitoneal shunts?

Yes. DESU offers Depus LP shunt kits in low, medium and high settings, with codes that begin LPDP, alongside its ventriculoperitoneal kits.

Related standards

• ISO 7197: Neurosurgical implants — Sterile, single-use hydrocephalus shunts and components
• ISO 13485: Medical devices — Quality management systems