SEBS prosthetic foot wedges: materials, performance and manufacturing for advanced orthopaedic applications

Materials science applied to orthopaedic medicine is undergoing a radical transformation, driven by the need to combine excellent biomechanical performance with an ever greater degree of device customisation.

In this context, SEBS has become the reference technical solution for critical components in high-performance prosthetic foot systems.

SEBS stands for Styrene-Ethylene-Butylene-Styrene, a thermoplastic elastomer belonging to the family of styrenic block copolymers.

Corti Srl produces in SEBS the shock-absorbing wedges of the ROADWALKINGIIHP prosthetic foot by Roadrunnerfoot Engineering, an Italian company specialising in the development of advanced orthopaedic devices. It is a small, almost invisible component that has a decisive effect on the quality of the prosthesis user’s gait.

In this article we look at the real-world use case: why SEBS is the ideal material for prosthetic foot wedges, how the wedges are made by injection moulding and what benefits they bring to the end user.

Why the material makes the difference in a high-performance prosthetic foot

A prosthetic foot is not a static object. During the gait cycle its components undergo thousands of cyclic stresses, including compression at heel contact, torsion in the stance phase and thrust in the propulsive phase.

In this context, choosing the most suitable material for shock-absorbing components is not a secondary matter, but decisive for a reliable, stable and long-lasting mechanical response.

SEBS as a prosthetic material: from chemistry to performance in use

SEBS is a thermoplastic block elastomer (TPE-S). The styrene segments provide stiffness and mechanical strength, while the ethylene-butylene blocks provide elasticity and flexibility.

The result is a material that behaves like vulcanised rubber at room temperature while keeping the processability of plastics, a key advantage for injection moulding.

Every physical property of the material is designed to meet specific needs of the orthopaedic application, as the table below shows.

Its properties also make it suitable for demanding scenarios such as the XIV Milano Cortina 2026 Paralympic Winter Games, where low temperatures, high speeds and rapid changes of slope put prosthetic components to a severe test.

A comparison with traditional elastomeric materials highlights its advantages even further. PVC, for example, needs plasticisers to achieve the required flexibility, and these often include phthalates, substances that migrate towards contact surfaces over time. Latex offers good initial elasticity but has other limits: besides the risk of allergic reactions, it degrades more quickly under cyclic mechanical stress.

SEBS overcomes these limits thanks to its molecular structure, which ensures reliability, consistent performance and safety over time.

In the following sections we show how adjusting the hardness of the material makes it possible to optimise comfort, performance and user well-being.

Further reading: for a complete overview of the technical characteristics of SEBS, see our article Discovering SEBS: technical properties and applications

SEBS, EVA and TPU compared: which material for a prosthetic wedge

Having looked at the advantages of SEBS over traditional materials, the table below compares its performance with two modern materials used for shock-absorbing components: EVA (ethylene vinyl acetate) and TPU (thermoplastic polyurethane).

SEBS proves to be a particularly well-balanced solution, because it combines higher resilience than EVA with greater thermal stability than TPU.

It is often an advantageous choice in terms of process sustainability too: all three materials are thermoplastics and therefore, in theory, recyclable, but in real applications recovering EVA and TPU can be more complex depending on the material structure and the production process. SEBS, on the other hand, is easier to remelt and reuse, which helps to reduce production waste.

The prosthetic foot and the role of the SEBS wedge

The ROADWALKINGIIHP is a K4-level prosthetic foot designed for highly active users. The device combines four carbon fibre laminates, produced with autoclave cycles derived from aerospace, with three ground contact points.

This unique configuration achieves an energy efficiency of up to 70% in some wedge configurations, one of the highest values recorded for this category of prosthesis.

Within this design, the shock-absorbing wedges produced by Corti Srl in SEBS perform a fundamental biomechanical function: absorbing the impact at heel contact (heel strike) and returning energy in a controlled way during the propulsive phase.

The ability of SEBS to dissipate kinetic energy and return it gradually reduces stress on the user’s residual joints and, at the same time, maximises the elastic return of the carbon fibre laminates.

Without a shock-absorbing wedge with the right properties, even the best carbon laminate could not deliver its full potential.

In this sense, the SEBS wedge is the link between the user’s biomechanics and the technology of the device, helping to turn the performance of the materials into efficient, stable and natural movement.

Soft or hard wedge: customisation according to the patient’s weight

One of the most innovative features of the prosthetic foot system is the availability of two versions of the SEBS wedge: the wedge soft and the wedge hard.

The wedge is chosen according to the user’s weight, to ensure a consistent and optimal mechanical response regardless of body build.

It is important to note that customising the wedge does not only affect sports performance: a prosthesis that does not correctly compensate for differences in weight can cause gait asymmetries, postural problems and chronic back pain.

Optimising the carbon fibre laminate – SEBS wedge system produces a load-deflection curve that faithfully reproduces the physiological function of the human foot-ankle complex, protecting the healthy limb from degenerative overload in the long term.

How Corti Srl produces SEBS wedges: injection moulding

The SEBS wedges are produced by injection moulding. In this case, the production flow includes:

• CAD modelling of the wedge geometry, optimised according to the force vectors of the gait cycle analysed by Roadrunnerfoot through gait analysis.
• Material preparation with dehumidification of the SEBS granules, with parameters set to prevent structural defects.
• Injection at controlled temperature between 160 °C and 220 °C, with parameters calibrated to ensure a homogeneous material.
• Controlled cooling to avoid internal stresses and deformation after demoulding.
• Manual deflashing and final quality control, with specific checks on the tolerances that are critical for gait biomechanics.

Finally, Industry 4.0 systems constantly monitor the processing parameters of the wedge, ensuring uniform elasticity, batch repeatability and optimal quality for gait biomechanics. In an application that directly affects the user’s quality of life, this level of control is an essential requirement.

Further reading: for a complete overview of our processes, see the page All Corti Srl capabilities

A use case that opens up new scenarios: where the same approach can be applied

This project shows that SEBS is a concrete engineering solution for applications that require long-term stability, no additive migration and a predictable mechanical response. Corti Srl processes SEBS in very different contexts.

The oil-free formulation, for example, does not only ensure adhesion between the prosthetic wedge and the carbon laminate: it is also used in the production of furniture feet for delicate surfaces such as untreated parquet, carpets and light-coloured rugs. Here the absence of migrating plasticisers ensures that no rings, residues or stains are left over time, a protection that no additional surface treatment can offer.

Further application examples include:

• Seals and flexible components for medical and parapharmaceutical devices
• Shock-absorbing elements for professional sports equipment
• Grip and ergonomic components for surgical and rehabilitation instruments
• Scratch-proof feet and supports for furniture, delicate floors and untreated surfaces
• Protective coatings in automotive and electronics, where thermal stability is critical

To discuss custom SEBS solutions, please contact us. Our technical team is available to help you choose and develop the solution best suited to your needs.

Article prepared by the Corti Srl Technical Department

FAQ

What is SEBS and why is it used in prosthetic feet?

SEBS is a biocompatible thermoplastic elastomer that keeps its elasticity and shape even after thousands of use cycles, which makes it ideal for the shock-absorbing components of prosthetic feet. Its styrenic block structure ensures thermal stability from -50 °C to +125 °C and is completely free from phthalates and latex. These properties are essential for devices in prolonged contact with the body that must perform reliably even in extreme climatic conditions.

What is the difference between a soft and a hard SEBS wedge?

The soft wedge is used for lighter users and the hard wedge for heavier users. The choice is technical, not subjective, because it determines joint health and gait quality over time. A wedge not suited to the patient’s weight can cause chronic back pain and joint problems if it is too soft, or gait asymmetries if it is too hard.

Why is SEBS better than EVA or TPU for a prosthetic wedge?

SEBS combines the advantages that EVA and TPU offer separately: higher resilience than EVA and greater thermal stability than TPU, and it can be formulated in different hardnesses according to the needs of each user. EVA tends to collapse under prolonged cyclic loads, while TPU stiffens at sub-zero temperatures; SEBS overcomes both limits thanks to its molecular structure.

Is SEBS safe for applications in contact with the body?

Yes. SEBS is inherently biocompatible and free from PVC, latex and phthalates. In addition, the oil-free formulation used by Corti Srl eliminates any risk of plasticisers migrating towards surfaces in contact with the body, ensuring long-term chemical stability.

How does Corti Srl produce a SEBS wedge?

Corti Srl produces the wedges by injection moulding. The process starts with CAD modelling, continues with the preparation and dehumidification of the granules and injection at controlled temperatures (160–220 °C), and ends with final quality control to millimetre tolerances. Every batch is monitored with Industry 4.0 systems to ensure repeatability, full traceability and optimal quality.

Is SEBS used only for prostheses?

No. Thanks to its properties, SEBS is useful in many other contexts. Corti Srl uses it, for example, for furniture feet in an oil-free formulation, where the absence of plasticisers prevents rings on untreated parquet, carpets and light-coloured rugs. Other applications include medical seals, shock-absorbing components for sports equipment and protective coatings in automotive.